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1
Burrell, Rhian. "Volcanic instability and associated uncertainties at Soufrière Hills Volcano, Montserrat and other volcanoes." Thesis, Lancaster University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435873.
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Bell, Andrew Forbes. "Patterns of volcano-tectonic seismicity at basaltic volcanoes." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444163/.
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Accelerating rates of volcano-tectonic (VT) earthquakes are a common precursor to volcanic eruptions and reflect fracture growth within the edifice. Theoretical models interpret the patterns in terms of failure of the volcanic edifice under the magmatic load and promise improved eruption forecasting. However, many eruptions at frequently active basaltic volcanoes are reported to begin with little change in the rate of VT earthquakes, apparently in conflict with edifice failure models. This thesis investigates the spatial and temporal patterns of VT earthquakes associated with eruptive and intrusive dyke injection at three of the best studied basaltic volcanoes, Kilauea and Mauna Loa (Hawaii) and Mt Etna (Sicily), in order to constrain the processes controlling the approach to eruption and test the applicability of edifice failure models. Approximately one third of dyke injection events are preceded by more than 4 weeks of exponentially accelerating rates of earthquakes. The trends are consistent with a model where deformation is controlled by the growth of independent fractures driven by increased magma pressure. Relations between acceleration parameters, such as the total number of earthquakes and characteristic timescale, provide information as to the likely timing of dyke injection. No evidence is found for short-term power-law accelerations in the rates of earthquakes thought to correspond to the linkage of fractures and observed at subduction zone volcanoes. The seismicity associated with the remaining events has characteristics indicating that flank instability is involved in triggering injection, either through the progressive reduction in the horizontal compressive stress by flank slip or through an episode of accelerated flank slip (a so-called slow earthquake). These observations suggest that: 1) an edifice failure model provides a good basis for understanding the approach to basaltic eruptions, but 2) at unstable volcanoes, modifications of the model are required to account for the influence of flank slip.
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Wetie, Ngongang Ariane. "Seismic and Volcanic Hazard Analysis for Mount Cameroon Volcano." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/60871.
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Mount Cameroon is considered the only active volcano along a 1600 km long chain of volcanic complexes called the Cameroon Volcanic Line (CVL). It has erupted seven times during the last 100 years, the most recent was in May 2000. The approximately 500,000 inhabitants that live and work around the fertile flanks are exposed to impending threats from volcanic eruptions and earthquakes.
In this thesis, a hazard assessment study that involves both statistical modelling of seismic hazard parameters and the evaluation of a future volcanic risk was undertaken on Mount Cameroon. The Gutenberg-Richter magnitude-frequency relations, the annual activity rate, the maximum magnitude, the rate of volcanic eruptions and risks assessment were examined.
The seismic hazard parameters were estimated using the Maximum Likelihood Method on the basis of a procedure which combines seismic data containing incomplete files of large historical events with complete files of short periods of observations. A homogenous Poisson distribution model was applied to previous recorded volcanic eruptions of Mount Cameroon to determine the frequency of eruption and assess the probability of a future eruption.
Frequency-magnitude plots indicated that Gutenberg-Richter b-values are partially dependent on the maximum regional magnitude and the method used in their calculation. b-values showed temporal and spatial variation with an average value of 1.53 ± 0.02. The intrusion of a magma body generating the occurrence of relatively small earthquakes as observed in our instrumental catalogue, could be responsible for this high anomalous b-value.
An epicentre map of locally recorded earthquakes revealed that the southeastern zone is the most seismically active part of the volcano. The annual mean activity rate of the seismicity strongly depends on the time span of the seismic catalogue and results showed that on average, one earthquake event occurs every 10 days. The maximum regional magnitude values which had been determined from various approaches overlap when their standard deviations are taken into account. However, the magnitude distribution model of the Mt. Cameroon earthquakes might not follow the form of the Gutenberg-Richter frequency magnitude relationship.
The datations of the last eruptive events that have occurred on Mt. Cameroon volcanic complex are presented. No specific pattern was observed on the frequency of eruptions, which means that a homogenous Poisson distribution provides a suitable model to estimate the rate of occurrence of volcanic eruptions and evaluate the risk of a future eruption. Two different approaches were used to estimate the mean eruption rate (λ) and both yielded a value of 0.074. The results showed that eruptions take place on average once every 13 years and, with the last eruption occurring over 15 years ago, it is considered that there is at present a high risk of an eruption to occur.Dissertation (MSc)--University of Pretoria, 2016.
Geology
MSc
Unrestricted
4
Armanno, Venero. "The volcano." Thesis, Queensland University of Technology, 1998.
Find full textAbstract:
The problems associated with marketing in China have been raised in several studies in the last 10 years. However, these prior studies focused on the four elements of
marketing mix for China and not on strategic marketing for the market in China, nor did they emphasise the implications of culture and marketing systems in China for developing strategic marketing plans.
This thesis has focused on building a general framework that could help Western firms, particularly Hong Kong-based, to develop strategic marketing plans that deal with
Chinese cultures and marketing systems in China. Therefore this thesis addresses the
research problem:How do wholly-owned Western firms in Hong Kong develop strategic marketing plans to do business in China? This research reviewed the available literature relating to cultures and marketing
systems in the West and China. By comparing and contrasting these differences, eleven research questions were formulated and shown as follow. In developing strategic marketing plans for the market in China: RQJ: how is market research as important a foundation for strategic marketing effectiveness as it is in the West?
RQ2: how is planning longer-term than in the West?
RQ3: how is the approach evolutionary rather than revolutionary, compared to the
West?
RQ4: how does strategy emphasise long-term relationships with and among consumers
(for example, by offering sales service) more than in the West?
RQ5: how does target marketing emphasise the group rather than the individual?
RQ6: how are product line strategies different.from those in the West?
RQ7: how do marketing strategies allow for less flexibility in price than in the West?
RQB: how will promotion strategies which Western firms can exercise within
distribution channels in China be similar to those used in the West?
RQ9: how are the choice of institutions and levels of channels in China different from
those in the West?
RQI Oa: how is market segmentation of consumers in China more difficult than in the
West?
RQllb: how can cultural differences between West and China be used as a basis for market segmentation?
As discussed in chapter 3, data were collected by using the case study methodology,with one pilot case study conducted in Brisbane to refine the research protocol and
procedure. In the major stage of data collection, six wholly-owned Western firms from different industries were interviewed and examined in Hong Kong. As discussed in chapter 4, data was analysed by using case descriptions, cross-case analysis and explanation building methods. Triangulation was carried out in order to ensure the findings and conclusion were convincing and generalisable.
The results of the research indicate that most of the methods for developing strategic marketing plans for the market in China (for example, market research, segmentation and targeting) are derived from the Western conventional marketing principles. However, the methods are relatively rudimentary and the approach tends to
evolutionary and emphasises relationships. Indeed, there are only a few similarities between strategic marketing planning in China and the West, with the differences being attributable in the main to cultural factors and marketing systems. The major contribution of the research was to provide far more detailed descriptions and
sometimes explanations of strategic marketing planning processes than those provided in the extant literature.
On the basis of these research findings, a model (refer table 5.2 and figure 5.1) has been built to help Western firms to develop strategic marketing plans that deal with
Chinese cultures and marketing systems.
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Saito, Takeshi. "Magnetic petrology of Yufu volcano and Unzen volcano, Japan." Kyoto University, 2004. http://hdl.handle.net/2433/147704.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第10945号
人博第232号
15||187(吉田南総合図書館)
新制||人||58(附属図書館)
UT51-2004-G792
京都大学大学院人間・環境学研究科環境相関研究専攻
(主査)教授 鎌田 浩毅, 助教授 石川 尚人, 助教授 酒井 敏
学位規則第4条第1項該当
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Smith, Cassandra M. "Volcanic Electrification: A Multiparametric Case Study of Sakurajima Volcano, Japan." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7950.
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Electrical activity at volcanoes has been recently recognized as a potential new remote sensing technique for plume-forming eruptions. Volcanic electrical activity takes place in the conduit and plume and therefore has the benefit of being a direct indicator of surface activity. This is unlike seismic signals, which indicate magma/gas movement underground, and infrasound signals, which indicate a surface explosion but not necessarily the formation of an ash plume. There are two distinct types of volcanic electrical discharges: volcanic lightning and continual radio frequency (CRF) impulses. This dissertation explores the relationships between these two electrical signals and other commonly monitored volcanic parameters. For volcanic electrical activity to be widely adopted into monitoring platforms it is important to understand how electrical discharges at volcanoes are related to other monitored signals. I present a case study of the electrical activity at Sakurajima Volcano, Japan. The lightning mapping array (LMA) is used to record both lightning and CRF. I relate CRF to ash properties and show that CRF corresponds to eruptions containing more juvenile magma that has undergone milling as it is transported out of the conduit. Seismic, infrasound, and video data are used in conjunction with multivariable statistical methods on a suite of electrical parameters to show that high levels of volcanic electrical activity are related to eruptions with large infrasound signals (> 107 J), high initial velocities (> 55 m/s), and relatively tall plume heights (> 1 km). Finally, an examination of globally detected lightning at Bogoslof Volcano, AK shows the potential for volcanic lightning in plume tracking (0-100 km), even after the end of the explosive phase of the eruption.
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Longobardi, Mariantonietta <1983>. "Locating the source of volcanic tremor at stromboli volcano, italy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5181/1/Tesi.pdf.
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We have developed a method for locating sources of volcanic tremor and applied it to a dataset recorded on Stromboli volcano before and after the onset of the February 27th 2007 effusive eruption. Volcanic tremor has attracted considerable attention by seismologists because of its potential value as a tool for forecasting eruptions and for better understanding the physical processes that occur inside active volcanoes. Commonly used methods to locate volcanic tremor sources are: 1) array techniques, 2) semblance based methods, 3) calculation of wave field amplitude. We have choosen the third approach, using a quantitative modeling of the seismic wavefield. For this purpose, we have calculated the Green Functions (GF) in the frequency domain with the Finite Element Method (FEM). We have used this method because it is well suited to solve elliptic problems, as the elastodynamics in the Fourier domain. The volcanic tremor source is located by determining the source function over a regular grid of points. The best fit point is choosen as the tremor source location. The source inversion is performed in the frequency domain, using only the wavefield amplitudes. We illustrate the method and its validation over a synthetic dataset. We show some preliminary results on the Stromboli dataset, evidencing temporal variations of the volcanic tremor sources.
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Longobardi, Mariantonietta <1983>. "Locating the source of volcanic tremor at stromboli volcano, italy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5181/.
Full textAbstract:
We have developed a method for locating sources of volcanic tremor and applied it to a dataset recorded on Stromboli volcano before and after the onset of the February 27th 2007 effusive eruption. Volcanic tremor has attracted considerable attention by seismologists because of its potential value as a tool for forecasting eruptions and for better understanding the physical processes that occur inside active volcanoes. Commonly used methods to locate volcanic tremor sources are: 1) array techniques, 2) semblance based methods, 3) calculation of wave field amplitude. We have choosen the third approach, using a quantitative modeling of the seismic wavefield. For this purpose, we have calculated the Green Functions (GF) in the frequency domain with the Finite Element Method (FEM). We have used this method because it is well suited to solve elliptic problems, as the elastodynamics in the Fourier domain. The volcanic tremor source is located by determining the source function over a regular grid of points. The best fit point is choosen as the tremor source location. The source inversion is performed in the frequency domain, using only the wavefield amplitudes. We illustrate the method and its validation over a synthetic dataset. We show some preliminary results on the Stromboli dataset, evidencing temporal variations of the volcanic tremor sources.
9
Fournier, Nicolas. "Shallow volcanic processes at persistently active volcanoes : evidence from a multidisciplinary study at PoaÌs volcano, Costa Rica." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411251.
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Letham-Brake, Mark. "Geological constraints on fluid flow at Whakaari volcano (White Island)." Thesis, University of Canterbury. Department of Geological Sciences, 2013. http://hdl.handle.net/10092/8728.
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This study assesses the geological constraints on fluid flow within the main crater of Whakaari volcano (White Island) which is located in the Bay of Plenty, New Zealand. A review of the volcanological and morphological history, field mapping, and permeability experiments were used to propose a model for single-state (gas or liquid water) fluid flow in the volcano. Three structural scales were of most importance: (a) the elongate main crater (1.2 km by 0.5 km); which contains (b) three subcraters (~300-500 m in diameter); and (c) >14 historic eruption craters and crater complexes (30-300 m in diameter).
A large (2.1x10⁸ m³) sector collapse formed the basic morphology and structure of the amphitheatre-like main crater ≤3.4 ka. Hot fluids are released from magma at ~1–2 km depth and circulated within a conduit-hosted volcano-hydrothermal system. The collapse event was likely to have removed low permeability cone lavas, significantly increasing meteoric water collection and lateral seawater infiltration within high permeability main crater fill above the magma conduit. It is proposed that this caused a susceptibility to ‘wet’ (i.e. phreatic and phreatomagmatic) eruptions which possibly formed three prehistoric subcraters and has been demonstrated in the last ~200 years of available historic record. The permeability of the remaining in-situ cone lavas is controlled by micro- (<1 mm) and macro- (>1 mm) cracks but despite these cracks, the cone lavas’ permeability is still sufficiently low to focus rising magmatic fluid flow through main crater fill. Low-to-high permeability lithified tuffs are inferred to fill the main crater at depth. Low permeability fine ash tuffs generally restrict vertical fluid flow put permit it when vertical trains of vesicles are present. Atmospheric steam and gas pluming is accommodated by a permeable zone of repeated and overlapping historic eruption crater-related discontinuities that extend to >250 m depth through highly permeable unlithified main crater fill in the west. It is likely to be this material into which the seawater infiltrates from the east. Throughout the main crater, fluid flow is focussed at subcrater margins due to steeply-dipping discontinuities between low permeability lava and low-to-high permeability crater fill deposits. The variable permeabilities of crater fill deposits are due to age-related factors of hydrothermal alteration, reworking/sorting, consolidation, and pore mineralisation. At shallow levels (<100 m depth), vertical fluid flow is diverted to historic eruption crater margins by very low permeability clay (reworked and altered tephra). High permeability coarse ash tuffs, Fe-rich lapilli tuffs, and surficial solfatara deposits do not appear to have much effect on the overall fluid flow system.
The results of this study show that, within active volcanic craters, the spatial distributions of variably permeable lithologies are often related to discontinuous cratering structures. Together, these are significant geological constraints on fluid flow. Morphological changes to crater structure can directly impact the groundwater regime above the magma conduit and may strongly influence the occurrence of wet versus dry eruptions. This process is possibly a significant control on eruptive behaviour at volcanoes with similar fluid flow systems worldwide.
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Saballos, Jose Armando. "Short and Long Term Volcano Instability Studies at Concepción Volcano, Nicaragua." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4757.
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Concepción is the most active composite volcano in Nicaragua, and is located on Ometepe Island, within Lake Nicaragua. Moderate to small volcanic explosions with a volcanic explosivity index (VEI) of 1-2 have been characteristic of this volcano during the last four decades. Although its current activity is not violent, its volcanic deposits reveal stages of violent activity involving Plinian and sub-Plinian eruptions that deposited vast amounts of volcanic tephra in the Atlantic Ocean. These observations, together with the 31,000 people living on the island, make Concepción volcano an important target for volcanological research.
My research focuses on the investigation of the stability of the volcano edifice of Concepción, using geophysical data such as gravity, geodetic global positioning system (GPS), sulphur dioxide (SO2) flux, real-time seismic amplitude (RSAM), and satellite remotely-sensed data. The integration of these data sets provides information about the short-term behavior of Concepción, and some insights into the volcano's long-term behavior.
This study has provided, for the first time, information about the shallow dynamics of Concepción on time scales of days to weeks. I furnish evidence that this volcano is not gravitationally spreading in a continuous fashion as previously thought, that its bulk average density is comparable to that of a pile of gravel, that the volcano edifice is composed of two major distinctive lithologies, that the deformation field around the volcano is recoverable in a matter of days, and that the deformation source is located in the shallow crust. This source is also degassing through the relatively open magmatic conduit. There are, however, several remaining questions. Although the volcano is not spreading continuously there is the possibility that gravitational spreading may be taking place in a stick-slip fashion. This has important implications for slope stability of the volcano, and the
associated hazards. The factors influencing the long term slope stability of the volcano are still not fully resolved, but internal volcanic processes and anthropogenic disturbances appear to be the major factors.
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Hidayati, Sri. "Study on volcano-tectonic earthquakes at Sakurajima volcano and its surroundings." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136776.
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Syahbana, Davy Kamil. "Seismological study of volcanic activity at Papandayan volcano, West Java, Indonesia." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209395.
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Dans l'histoire des éruptions volcaniques, le Papandayan à l'Ouest de Java est considéré comme l'un des plus meurtriers après avoir causé la mort de 2957 personnes et des dégâts sérieux en 1772. L'éruption la plus récente de ce volcan a eu lieu en 2002 et était de type phréatique. Cette éruption a été précédée d'une augmentation soudaine de l'activité sismique moins de deux jours avant l'éruption. Aucune victime n'a été déplorée. La nature de cette éruption est indéfinie. Cette thèse regroupe plusieurs études utilisant différentes techniques en vue d'améliorer la prédictibilité des éruptions du volcan Papandayan, principalement via l'interprétation des signatures sismiques.Le monitoring sismique passif a débuté en décembre 2009 par l'installation d'une station sismique permanente à large bande dans le cratère du Papandayan. L'année suivante, une station météorologique a été installée pour compléter les mesures. La troisième année, 8 stations sismiques temporaires ont été déployées autour du volcan en réponse à une augmentation de l'activité sismique en 2011.
Nous avons conduit différentes études; (1) Nous avons examiné l'évolution de l'activité volcanique par réalisation d'une revue complète de l'histoire éruptive du volcan, autant pour la période préhistorique qu'historique. (2) Nous avons réalisé une analyse temps-fréquence des événements sismiques, étudié leurs caractéristiques et proposé une nouvelle classification avec une description des processus physiques supposés les générer. (3) Nous avons étudié les signatures sismiques précurseur de l'éruption de 2002 et pendant la crise volcanique de 2011 en implémentant différentes méthodologies, dont: la détection automatique d'événements sismiques à l'aide de filtres récursifs STA/LTA, l'analyse spectrale des formes d'onde, la mesure continue de l'amplitude spectrale du signal (SSAM), la polarisation des ondes et l'analyse de la distribution fréquence/magnitude (b-value). Nous avons alors réalisé un modèle chronologique des séquences sismiques du Papandayan. (4) Pour améliorer la compréhension de la dynamique des fluides sous le volcan Papandayan, nous avons réalisé une analyse des fréquences complexes des événements longue période (LP) et leurs variations temporelles peuvent être utilisées pour estimer (a) la composition des fluides présents dans les fractures sous le volcan et/ou (b) l'évolution des dimensions de ces fractures. Ces variations des fréquences complexes des événements LP peuvent être interprétées comme les réponses dynamiques du système hydrothermal à des changements d'impulsions de chaleur transférées par les flux de gaz volcaniques du magma sous le volcan. (5) nous avons calculé l'évolution temporelle du rapport spectral horizontal-sur-vertical (HVSR) en utilisant le bruit sismique ambiant enregistré par une station unique pour estimer les variations de vitesse de propagation des ondes de cisaillement en lien avec l'activité dynamique du volcan. Nous avons trouvé une corrélation claire entre les variations de fréquence de résonnance HVSR et l'augmentation de la sismicité.
Enfin, nous proposons des hypothèses sur les processus physiques qui se produisent sous le Papandayan. Cette étude est une première tentative d'utilisation de cette méthode pour surveiller l'activité volcanique en continu.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Johnstone, Jade. "Rainfall induced volcanic activity on Soufriere Hills Volcano, Montserrat, West Indies." Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490615.
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Extremely hazardous volcanic dome collapse and pyroclastic flows can occur without warning and can be triggered by intense rainfall. Rainfall data collected on Soufriere Hills Volcano, Montserrat between 1998 and 2006 was analysed to assess the impact on primary volcanic activity, defined here as pyroclastic flows, dome collapse and explosions and to explore the utility of meteorological data as a predictive tool for active volcanoes. A statistical analysis of daily rainfall totals and volcanic activity, showed that if greater than 20 mm of rainfall fell on a particular day the probability of a dome collapse occurring on that day increased by a factor of 6.2 from 1.0% to 6.1%, similarly the probability of observing pyroclastic' flows and explosions increased by factors of 2.0 and 4.3 respectively. These statistically significant links increased as the rainfall threshold increased, and in some cases activity was observed up to 48 hrs after rainfall. The state of the volcano is important and an absence of a significant volume of material above the conduit removes the possibility that rainfall could trigger a collapse. An analysis of a network of 1 minute resolution rainfall and seismic data for the period 1 January 2001 - 31 December 2003 showed a correlation, statistically significant to the 99% level was found between rainfall and heightened activity; rockfalls, long period earthquakes, long period rockfalls and hybrid earthquakes. There were three prominent peaks in magnitUde, following a rainfall event of 5 mm hr-I at time lags of approximately 5, 14 and 25 hours. Over 50% of the heavy rainfall days were associated with synoptic scale weather systems which are potentially well predicted by current forecast models. However the remaining days were associated with localized and essentially unpredictable systems. There was significant variability between raingauges reflecting topographic variations and inherent variability within weather systems, hence any monitoring program is recommended to use a network rather than a single gauge. Incorporation of weather forecasting into hazard monitoring programs would help to improve the prediction of hazardous collapses.
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Ebmeier, Susanna Kathryn. "InSAR measurements of volcano deformation on the Central American Volcanic Arc." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:c015fe2a-f4dc-49db-b150-a2ab00ba8f5b.
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Satellite measurements of volcano deformation have the potential to illuminate a wide range of volcanic processes and have provided us with the first opportunity to investigate volcano deformation as an arc-scale process. This thesis presents the results of an Interferometric Synthetic Aperture Radar (InSAR) survey of the Central American Volcanic Arc between 2007 and 2010. My measurements confirm a statistically significant absence of magmatic deformation in Central America relative to other well-studied volcanic arcs. I estimate a minimum detection threshold for deformation at 20 of the arc’s 26 active volcanoes using time series analysis of interferometric phase. I find that the majority (∼80%) of literature measurements of volcano deformation made at other arcs would have been possible with the average magnitude of noise in Central American volcanoes. The absence of measurable magmatic deformation in Central America may therefore be due to factors that limit the geodetic expression of magma movement, including the deep pooling of basalts and high parental melt volatile content. The quantification of measurement uncertainty also allows me to use the lack of deformation at specific erupting volcanoes to make order of magnitude estimations of the minimum depth for magma storage that would not result in measurable deformation. I present measurements and interpretation of non-magmatic deformation associated with edifice development at two Central American volcanoes: Arenal, Costa Rica and Santiaguito, Guatemala. At Arenal, I measure apparently steady slip (∼7 cm/yr) on the volcano’s western flanks, which I attribute to gravity-driven slip on the boundary between lavas emplaced over the past 50 years and older tephras and paleosols. At Santiaguito, I demonstrate the measurement of large-scale (∼10-200 m) topographic change from a small set of large baseline interferograms. Measurements of post-2000 lava fields allow me to estimate extrusion rate, map changes to flow morphology and make simultaneous measurements of lava flow thickness and subsidence rate.
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Rawson, Harriet. "Volcanic history and magmatic evolution of Mocho-Choshuenco Volcano, southern Chile." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:05969e3b-4f38-4478-bc26-381ca13bce1d.
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Active volcanoes pose a significant natural hazard. In order to evaluate the hazard it is important to reconstruct the history of such volcanoes to understand the frequency, style of eruption and the areas typically affected by the explosive eruptions. This thesis focuses on deciphering the volcanic and magmatic record for one of the most productive volcanoes in southern Chile, Volcán Mocho-Choshuenco. Work presented in the thesis establishes a detailed record of the explosive activity during the last 18 kyrs, constructed using field observations and geochemical analyses of the eruption deposits. Using a multi-technique approach Mocho-Choshuenco is shown to be one of the most explosive, frequently active and hence hazardous volcanoes in Chile. This high-resolution eruptive record provides new constraints on the underlying causes of spatial and temporal variability in arc volcanism. Temporally, the record gives new understanding into the response of arc volcanoes to deglaciation; clear temporal variation in eruption flux, eruption size and magma composition are observed. This time-varying behaviour is hypothesised to reflect changes in the crustal plumbing system, and magma storage timescales in response to removal of an ice-load. It demonstrates that deglaciation can drive changes in eruption behaviour at arc volcanoes; however the response is more complex and subtle than settings where decompression melting dominates. Spatially, Mocho-Choshuenco has a high number and density of scoria cones that have erupted relatively primitive magmas but nonetheless with a wide range of magma compositions. For some of the 'classical' slab and mantle geochemical tracers the erupted magmas span the complete range seen in this part of the arc. The tight temporal and spatial constraints provided by the analysed samples, coupled with recent advances in numerical modelling of magma transport through subduction zones, enable new hypotheses for interpreting the signatures of mafic arc magmas to be defined.
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Aydar, Erkan. "Etude volcano-structurale et magmatologique du strato-volcan hasan dagi (anatolie centrale-turquie)." Clermont-Ferrand 2, 1992. http://www.theses.fr/1992CLF21446.
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Le hasan dagi, strato-volcan d'anatolie centrale (turquie), comprend 2 cones terminaux: grand hasan dagi (3253 m) et petit hasan dagi (3069 m). Son volume est estime a 354 km#3 et il couvre une superficie de 760 km#2 environ. Une approche pluri-disciplinaire nous a permis de retracer son evolution volcano-structurale, dynamique (styles eruptifs) et magmatologique. Nous avons distingue 3 grands stades d'evolution au cours de son histoire: 1) systeme de kecikalesi (13 ma environ) presente une depression d'origine calderique. Les caracteres mineralogiques et geochimiques (presence de pigeonite et affinite tholeiitique) en font un systeme independant du hasan dagi (s. S. ); 2) le paleo-hasan dagi (7 ma environ) est constitue d'empilement de coulees d'andesites basaltiques, lahars et ignimbrites rhyolitiques. Ce dernier episode conduit a l'effondrement d'une caldera. Les caracteres mineralogiques et geochimiques sont similaires a kecikalesi, a l'exception de la presence de grenat microlitique dans les laves et les ignimbrites du paleo-hasan dagi; 3) le hasan dagi (s. S. ) s'est edifie en deux etapes (le meso-hasan dagi et le neo-hasan dagi) caracterisees par 2 stades calderiques. Les produits sont des domes-coulees andesitiques, dacitiques et plus rarement rhyolitiques, avec nuees ardentes associees, des nappes d'ignimbrites rhyodacitiques et rhyolitiques et des breches intrusives. Les dernieres eruptions datent de moins de 6000 ans. Le melange magmatique est a l'origine des laves intermediaires. La serie calco-alcaline moyennement potassique est complete (basalte a rhyolite). Les termes les plus differencies sont fortement potassiques. D'autre part, un volcanisme basaltique accompagne tous les appareils centres. Nous avons distingue 3 generations: premiere generation, liee aux edifices anciens (kecikalesi et paleo-hasan dagi) a opx; deuxieme generation, interstratifiee dans la serie du meso-hasan dagi; troisieme generation, contemporaine du neo-hasan dagi calco-alcalin, a mineralogie de basaltes alcalins (feldspaths potassiques, nepheline normative, cpx de basaltes intraplaques), mais affinite orogenique. Sur le plan geochimique, certains de ces basaltes contiennent des microlites de grenat automorphe; dont l'origine est a rapporter a un processus de fusion partielle (croute subductee ou croute inferieure)
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Selles, Adrien. "Multi-disciplinary study on the hydrogeological behaviour of the Eastern flank of the Merapi Volcano, Central Java, Indonesia." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066690.
Full textAbstract:
Les connaissances actuelles sur le comportement hydrogéologique des édifices volcano-détritique sont encore limitées et cela limite la bonne gestion des ressources en eau. Depuis une décennie, sur les flancs du volcan Merapi, à Java Centre, en Indonésie, une pression croissante se fait sur la ressource en eau avec l'intensification des pratiques agricoles irriguées, la croissance de la population et les utilisations industrielles de l'eau. Le manque de connaissances sur les processus du cycle de l'eau par les consommateurs déclenche des conflits d'usage et le partage de l'eau devient une question centrale. Une compréhension plus précise du cycle de l'eau dans sa globalité dans ce genre de contexte est donc un point fondamental qui a besoin d'être amélioré.Ce travail a été axé sur la caractérisation des ressources en eaux souterraines à travers l’étude de la géométrie et des propriétés hydrodynamiques des systèmes aquifères /aquitards multi-couches à l'échelle d’un bassin versant expérimental sur le flanc Est du volcan Merapi. Pour couvrir tous les processus impliqués dans la circulation des eaux souterraines, une approche multi-disciplinaire a été choisi.Une nouvelle approche géologique et géomorphologique a été réalisé afin de caractériser la structure interne et l'architecture de dépôt sur le flanc Est du Merapi. Sur la base de ces résultats, un modèle conceptuel géologique et géomorphologique a été construit et révèle des formations détritiques chenalisées et connectées depuis les hautes altitudes jusqu’aux vallées, créant des chemins préférentiels pour les eaux souterraines.La caractérisation du climat avec l'estimation des termes du bilan hydrique et la description des principaux processus hydrologiques sont décrits par le suivi de deux années hydrologiques (2011-2012 et 2012-2013 ). Le climat tropical de cette région se caractérise par une période de mousson (Novembre à Mai ) et une saison sèche (Juin à Octobre ). Le bilan hydrologique est caractérisé par 40 % des précipitations sont perdus par évapotranspiration, 10 % s'écoulent et la moitié restante s'infiltre à travers l'édifice volcano-détritique et recharge les aquifères multicouches.Le fonctionnement hydrogéologique d'un environnement volcano-détritique complexe a pu être appréhendé à l’aide d’un suivi hydrogéologique, hydrochimique et géochimiques sur les sources et des puits peu profonds. Deux ceintures de sources ont été identifiées: la première est caractérisée par des sources de dépression alignées le long d'une ligne topographique tandis qu'une faille normale est probablement à l'origine de la seconde. L’utilisation de la température de l’eau de source comme traceur de l’altitude de recharge a permis l’identification de plusieurs systèmes aquifères multi-couches. Les propriétés hydrauliques de ces aquifères ont été établi à partir des l'analyses des essais hydrauliques. Le premier système aquifère est situé proche de la surface et possède une faible conductivité hydraulique. En revanche, un second système aquifère a été identifié en profondeur et possède une forte perméabilité. Le traceur “température” met en évidence un effet de mélange entre le premier et le deuxième aquifère au niveau des sources de basses altitudes . Ce phénomène est confirmé par les résultats des analyses isotopiques.L'application d'un modèle numérique couplant la circulation des flux, le transfert de masse ou le transfert de chaleur confirme le modèle conceptuel hydrogéologique et permet de quantifier la ressource en eauThe current knowledge on the hydrogeological behavior of the volcano-detritic edifices is still sparse and these lacks limit the attempting of water resource management. Since a decade, on the flanks of Merapi volcano, in Central Java, Indonesia, an increasing pressure is done on the water resource with the intensification of the irrigated agriculture practices, the growth of population and the water industrial uses. The lack of knowledge about the water cycle processes by the consumers triggers water use conflicts and the water sharing becomes a central issue. A most accurate understanding of the water cycle in its globality in this kind of context is hence a fundamental point that need to be improved.This work has been focused on the characterization of groundwater resource thought the identification of the extent, the geometry and hydrodynamic properties of the aquifers/aquitards multi-layered system at the experimental catchment scale on the Eastern flank of Merapi volcano. To cover all the processes involved into the groundwater circulation, a multi-disciplinary approach has been chosen.A new geological and geomorphological approach is performed to characterize the internal structure and the deposit architecture on this zone of the Eastern flank of the Merapi. Based on these results, a geological and geomorphological conceptual model has been built and insists on the channelized detritic formations connected from the upper parts to the low lands through the volcanic edifice and that create preferential groundwater path ways.The climate characterization with the estimation of the water balance terms and the description of main hydrological processes are described with the monitoring of two hydrological years (2011-2012 and 2012- 2013). The tropical climate of this region is characterized by seasonal monsoon (November to May) and dry season (June to October). The global water balance can be distributed as follow: 40% of rainfall are lost by evapotranspiration, 10% runs off and the remaining half infiltrates through the volcano-detritic edifice to recharge the multi-layered aquifers.The hydrogeological functioning of a complex volcano-detritic environment is explained through the implementation of hydrogeological, hydrochemical and geochemical monitoring on inventoried springs and wells. Two spring belts are described, the first one is characterized by depression spring along a topographic line while a normal fault is probably at the origin of the second one. The identification of a multi-layered aquifer systems has been done based on the determination of the spring water temperature as a relevant tracers of the recharge elevation and the groundwater circulations. The hydraulic properties of these aquifers have been investigated from the analysis of hydraulic tests. Results show a low permeable aquifer close to the surface with a local recharge while a second aquifer system with high permeability and regional recharge is located deeper. The tracer temperature shows a mixing effect between the first and the second aquifers in the springs at low elevation. This phenomenon is confirmed by the isotope analysis.The application of a coupled numerical model between flow circulation, first mass transfer and second heat transfer confirms the hydrogeological conceptual model of volcano-sedimentary edifice and allows to quantify the water resource
19
Milawski, James. "Quaternary Volcanic Ash Transformation in the Mayan Lowland." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377871595.
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Ulusoy, Inan. "Etude volcano-structurale du volcan Nemrut (Anatolie de l'Est, Turquie) et risques naturels associés." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2008. http://tel.archives-ouvertes.fr/tel-00730602.
Full textAbstract:
Le volcan actif Mont Nemrut, situé à l'ouest du lac Van, est l'un des volcans les plus importants d'Anatolie orientale. Il possède une caldeira sommitale de 8.5 x 7 km de diamètres. L'activité volcanique du Nemrut a commencé il y a ~ 1Ma et s'est poursuivie jusque dans les périodes historiques. Les éruptions les plus récentes ont été signalées en 1441, 1597 et 1692 A.D. Parmi les volcans anatoliens orientaux, le Nemrut est le volcan le plus dangereux, compte tenu de sa proximité avec des sites urbanisés environnants ; il menace directement 135 000 habitants. Les manifestations actuelles de l'activité volcanique sont représentées par une activité hydrothermale et fumerollienne au sein de la caldeira. L'évolution structurale du volcan se subdivise en deux stades principaux ( pré-caldeira et post-caldeira) séparés par l'effondrement catastrophique de la caldeira. Les produits de l'activité anté-caldeira sont majoritairement représentés par des écoulements et des dômes de lave felsiques. Les séries ignimbritiques du Nemrut et de Kantasi, manifestations majeures de l'activité de la caldeira, sont constituées d'unités pliniennes et d'écoulements ignimbritiques. L'activité post-caldeira est représentée par une activité phréatomagmatique explosive et une activité effusive basaltique-rhyolitique bimodale, concentrées au sein de la caldeira et au niveau de la zone de rift récent du Nemrut, sur le flanc nord. L'analyse des données multisources (études de polarisation spontanée, modèles numériques de terrain et bathymétrie ainsi que de leurs produits dérivés, images Landsat et ASTER) a permis de caractériser la structure de la caldeira du Nemrut et les circulations hydrothermales associées. La synthèse de ces approches pluri-thématiques et des interprétations correspondantes permet de proposer que la caldeira est constituée de 3 blocs principaux, conséquence des processus de fragmentation générés lors des phases d'effondrement. Les frontières délimitant ces blocs et la frontière structurale principale de la caldeira contrôlent les principales activités hydrothermales intra-caldeira. Le régime tectonique régional de compression-extension existant au Pliocène est structuralement enraciné et est responsable du déclenchement du volcanisme du Mont Nemrut. Le jeu de systèmes décrochants surimposés aux structures pré-existantes a provoqué l'apparition d'une zone de faiblesse localisée au sein de laquelle le système volcanique du Nemrut s'est préférentiellement mis en place. La surveillance de l'activité du volcan a été initiée par l'installation d'un ensemble de 3 sismomètres, ce qui constitue le 1er réseau de surveillance sismo-volcanique sur un volcan en Turquie. Les données temps réel sont acquises, traitées et archivées depuis octobre 2003. L'interprétation des signaux volcaniques acquis dans le cadre de cette surveillance sismologique, couplée aux résultats de l'étude du système hydrothermal, confortent clairement l'existence d'une chambre magmatique active localisée aux environs de 4-5 km de profondeur. La surveillance à long terme de ce volcan potentiellement actif est essentielle pour la prévention des risques associés et fournira de plus une base de données essentielle pour une meilleure connaissance et compréhension du mode de fonctionnement de ce volcan.
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Maussen, Katharine. "Carbon dioxide transport through Taal volcano’s hydrothermal system and Main Crater Lake (Philippines)." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/271649.
Full textAbstract:
The presence of a hydrothermal system at Taal volcano is evident from the presence of a craterlake (Main Crater Lake, MCL), a caldera lake (Lake Taal) and several hot springs on the flanksof Taal volcano island and in the crater. Taal MCL, covering an area of 1.2 km², is acidic (pH= 3), warm (T = 30-33 °C) and its composition is dominated by Cl, Na and SO4. This thesisaims at understanding the geochemistry of Taal volcano’s hydrothermal system and the wayCO2 is transported through the hydrothermal system and MCL towards the atmosphere.The long-term geochemical evolution of MCL indicates that the hydrothermal system is madeof two reservoirs, one being volcanic and one geothermal in origin. The geothermal componentin Taal MCL has stayed rather constant since 1991, while the volcanic component hasdecreased.The low pH makes Taal volcano the perfect natural laboratory to study the behaviour of CO2,because there is no dissociation of CO2. A combined approach of total CO2 flux measurementsvia accumulation chamber and gaseous CO2 flux measurements via echo sounder shows thatmore than 90% of the total CO2 output of Taal volcano is due to the influx of dissolved CO2,migrating from the hydrothermal system to MCL via thermal springs under the lake surface.After verification of both horizontal and vertical homogeneity of dissolved CO2 concentrations,a continuous monitoring station was installed in 2013, measuring dissolved CO2 using aninfrared gas analyser protected by an ePTFE membrane, as well as several meteorological andenvironmental parameters. Several environmental and lacustrine processes influence CO2transport in MCL, including stratification, solar heating and rainfall.Taal volcano regularly goes through periods of unrest, characterised by seismic swarms,ground deformation and increased carbon dioxide flux. In 1991-1994, this was accompaniedby geochemical changes in MCL, including pH decrease and F, Si and Fe concentrationincrease. These changes can be attributed to an intrusion of magma to shallow levels less thanone kilometre deep. More recent unrests do not show these geochemical changes and are likelycaused by pressure changes in the hydrothermal system. The permanent monitoring stationrecorded hourly data on the 2015 unrest and showed that abnormally high CO2 concentrationswere recorded before the start of seismic or deformation activity, which makes continuous CO2monitoring a very valuable addition to current monitoring activities at Taal volcano.La présence d’un système hydrothermal au volcan Taal se manifeste par la présence d’un lac de cratère (Main Crater Lake, MLC) ainsi qu’un lac de caldera (Lake Taal) et de multiples sources d’eau chaudes sur les flancs et dans le cratère. Le MCL, avec une surface de 1.2 km², est acide (pH = 3), chaud (T = 30-33 °C) et composé principalement de Cl, Na et SO4. Le but de cette thèse est de comprendre la géochimie du système hydrothermal du Taal et la manière dont le CO2 est transporté à travers de celui-ci ainsi qu’à travers le MCL vers l’atmosphère. L’évolution géochimique à long terme indique que le système hydrothermal est composé de deux réservoirs, un d’origine volcanique et un autre d’origine géothermale. Le composant géothermal est resté plutôt constant depuis 1991, tandis que le composant volcanique a diminué. Le pH plutôt bas fait que le volcan Taal est le laboratoire naturel parfait pour étudier le comportement du CO2, parce qu’il n’y a pas de dissociation de CO2. Une approche combinée du flux de CO2 total via chambre d’accumulation, et flux de CO2 gazeux via echo sondeur montre que plus que 90% du flux de CO2 total est dû au CO2 dissout, qui migre depuis le système hydrothermal au MCL via des sources thermales sous la surface du lac. Après vérification de l’homogénéité horizontale et verticale du CO2 dissout, une station de monitoring en continu a été installée en 2013. Cette station mesure le CO2 dissout à l’aide d’un analyseur de gaz infrarouge protégé par une membrane en ePTFE, ainsi que de multiples paramètres météorologiques et environnementaux. Le transport de CO2 dans le MCL est influencé par plusieurs processus environnementaux et lacustre, comprenant la stratification, l’échauffement solaire et la pluie. Le volcan Taal connait régulièrement des périodes de crises caractérisées par une activité sismique, par une déformation du sol et par un flux élevé du CO2. En 1991-1994, ceux-ci ont été accompagnés par des changements géochimiques du MCL, comprenant une diminution du pH et une augmentation de la concentration de F, Si et Fe. Ces changements peuvent être attribués à une intrusion superficielle de magma à moins d’un kilomètre de profondeur. Les crises plus récentes ne montrent pas ces changements en géochimie et sont probablement causés par des changements de pression dans le système hydrothermal. La station de monitoring en continu a enregistré des données toutes les heures pendant la crise en 2015 et a montré que des concentrations particulièrement élevées en CO2 dissout ont été enregistrées avant le début de l’activité sismique et de déformation. Ceci a montré que le monitoring en continu du CO2 est une addition très précieuse aux activités de monitoring du volcan Taal.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
22
Selles, Adrien. "Multi-disciplinary study on the hydrogeological behaviour of the Eastern flank of the Merapi Volcano, Central Java, Indonesia." Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066690.
Full textAbstract:
Les connaissances actuelles sur le comportement hydrogéologique des édifices volcano-détritique sont encore limitées et cela limite la bonne gestion des ressources en eau. Depuis une décennie, sur les flancs du volcan Merapi, à Java Centre, en Indonésie, une pression croissante se fait sur la ressource en eau avec l'intensification des pratiques agricoles irriguées, la croissance de la population et les utilisations industrielles de l'eau. Le manque de connaissances sur les processus du cycle de l'eau par les consommateurs déclenche des conflits d'usage et le partage de l'eau devient une question centrale. Une compréhension plus précise du cycle de l'eau dans sa globalité dans ce genre de contexte est donc un point fondamental qui a besoin d'être amélioré.Ce travail a été axé sur la caractérisation des ressources en eaux souterraines à travers l’étude de la géométrie et des propriétés hydrodynamiques des systèmes aquifères /aquitards multi-couches à l'échelle d’un bassin versant expérimental sur le flanc Est du volcan Merapi. Pour couvrir tous les processus impliqués dans la circulation des eaux souterraines, une approche multi-disciplinaire a été choisi.Une nouvelle approche géologique et géomorphologique a été réalisé afin de caractériser la structure interne et l'architecture de dépôt sur le flanc Est du Merapi. Sur la base de ces résultats, un modèle conceptuel géologique et géomorphologique a été construit et révèle des formations détritiques chenalisées et connectées depuis les hautes altitudes jusqu’aux vallées, créant des chemins préférentiels pour les eaux souterraines.La caractérisation du climat avec l'estimation des termes du bilan hydrique et la description des principaux processus hydrologiques sont décrits par le suivi de deux années hydrologiques (2011-2012 et 2012-2013 ). Le climat tropical de cette région se caractérise par une période de mousson (Novembre à Mai ) et une saison sèche (Juin à Octobre ). Le bilan hydrologique est caractérisé par 40 % des précipitations sont perdus par évapotranspiration, 10 % s'écoulent et la moitié restante s'infiltre à travers l'édifice volcano-détritique et recharge les aquifères multicouches.Le fonctionnement hydrogéologique d'un environnement volcano-détritique complexe a pu être appréhendé à l’aide d’un suivi hydrogéologique, hydrochimique et géochimiques sur les sources et des puits peu profonds. Deux ceintures de sources ont été identifiées: la première est caractérisée par des sources de dépression alignées le long d'une ligne topographique tandis qu'une faille normale est probablement à l'origine de la seconde. L’utilisation de la température de l’eau de source comme traceur de l’altitude de recharge a permis l’identification de plusieurs systèmes aquifères multi-couches. Les propriétés hydrauliques de ces aquifères ont été établi à partir des l'analyses des essais hydrauliques. Le premier système aquifère est situé proche de la surface et possède une faible conductivité hydraulique. En revanche, un second système aquifère a été identifié en profondeur et possède une forte perméabilité. Le traceur “température” met en évidence un effet de mélange entre le premier et le deuxième aquifère au niveau des sources de basses altitudes . Ce phénomène est confirmé par les résultats des analyses isotopiques.L'application d'un modèle numérique couplant la circulation des flux, le transfert de masse ou le transfert de chaleur confirme le modèle conceptuel hydrogéologique et permet de quantifier la ressource en eauThe current knowledge on the hydrogeological behavior of the volcano-detritic edifices is still sparse and these lacks limit the attempting of water resource management. Since a decade, on the flanks of Merapi volcano, in Central Java, Indonesia, an increasing pressure is done on the water resource with the intensification of the irrigated agriculture practices, the growth of population and the water industrial uses. The lack of knowledge about the water cycle processes by the consumers triggers water use conflicts and the water sharing becomes a central issue. A most accurate understanding of the water cycle in its globality in this kind of context is hence a fundamental point that need to be improved.This work has been focused on the characterization of groundwater resource thought the identification of the extent, the geometry and hydrodynamic properties of the aquifers/aquitards multi-layered system at the experimental catchment scale on the Eastern flank of Merapi volcano. To cover all the processes involved into the groundwater circulation, a multi-disciplinary approach has been chosen.A new geological and geomorphological approach is performed to characterize the internal structure and the deposit architecture on this zone of the Eastern flank of the Merapi. Based on these results, a geological and geomorphological conceptual model has been built and insists on the channelized detritic formations connected from the upper parts to the low lands through the volcanic edifice and that create preferential groundwater path ways.The climate characterization with the estimation of the water balance terms and the description of main hydrological processes are described with the monitoring of two hydrological years (2011-2012 and 2012- 2013). The tropical climate of this region is characterized by seasonal monsoon (November to May) and dry season (June to October). The global water balance can be distributed as follow: 40% of rainfall are lost by evapotranspiration, 10% runs off and the remaining half infiltrates through the volcano-detritic edifice to recharge the multi-layered aquifers.The hydrogeological functioning of a complex volcano-detritic environment is explained through the implementation of hydrogeological, hydrochemical and geochemical monitoring on inventoried springs and wells. Two spring belts are described, the first one is characterized by depression spring along a topographic line while a normal fault is probably at the origin of the second one. The identification of a multi-layered aquifer systems has been done based on the determination of the spring water temperature as a relevant tracers of the recharge elevation and the groundwater circulations. The hydraulic properties of these aquifers have been investigated from the analysis of hydraulic tests. Results show a low permeable aquifer close to the surface with a local recharge while a second aquifer system with high permeability and regional recharge is located deeper. The tracer temperature shows a mixing effect between the first and the second aquifers in the springs at low elevation. This phenomenon is confirmed by the isotope analysis.The application of a coupled numerical model between flow circulation, first mass transfer and second heat transfer confirms the hydrogeological conceptual model of volcano-sedimentary edifice and allows to quantify the water resource
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Jeddi, Zeinab. "Seismological Investigation of Katla Volcanic System (Iceland) : 3D Velocity Structure and Overall Seismicity Pattern." Doctoral thesis, Uppsala universitet, Institutionen för geovetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303342.
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The work in this thesis concentrates on Katla volcano in southern Iceland. This is one of Europe’s most active volcanoes and its history tells us that it poses many threats to society, both locally (Iceland) and on a broader scale (Europe). Its geological setting is complex, where the effects of a melting anomaly in the mantle and a changing rift geometry, perturb the classical setting of volcanism in a rifting setting. The work has focused on two aspects. The first is the varying distribution of physical properties in the subsurface around the volcano. The second is the distribution of microearthquakes around the volcano. The physical properties that we study are the speeds of seismic waves that reflect variations of temperature, composition and fracturing of the rocks. These can, therefore, help us learn about long-term processes in the volcano. The seismicity gives shorter-term information about deformation associated with current processes. I have applied two tomographic techniques to study Katla’s subsurface to a depth of 5-10 km, namely local-earthquake and ambient-noise tomography. The former makes use of the timing of waves generated by local earthquakes to constrain the earthquakes’ locations and the distribution of wave speed. Here I have concentrated on compressional waves or P waves with a typical frequency content around 10 Hz. With the latter, surface waves are extracted from microseismic noise that is generated far away at sea and their timing is measured to constrain their wave-speed distribution, which then is used to map shear-wave velocity variations. This is done at a typical frequency of 0.3 Hz. I find that the volcano contains rocks of higher velocity than its surroundings, that Katla’s caldera is underlain by low velocities at shallow depth that may be explained by hot or partially molten rocks and that beneath the caldera lies a volume of particularly high velocities that may constitute differentiated cumulates. But, I also find that it is not simple to compare results from such different wave types and discuss a number of complications in that regard. In addition to the well-known microearthquake distribution in the caldera region of Katla and to its west, we have discovered two additional areas of microearthquake activity on the volcano’s flanks, south and east of the caldera. These point to current activity and are, therefore, of interest from a hazard point of view. However, it is difficult to pinpoint their underlying process. Speculation about possible interpretation leads me to hydrothermal processes or small pockets of melt ascending due to their buoyancy or locally enhancing fluid pressure, thereby lowering the effective stress.
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Perälä, Jesper. "Pit Craters of Arsia Mons Volcano, Mars, and Their Relation to Regional Volcano-tectonism." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-255563.
Full textAbstract:
Pit crater and pit crater chains associated to the volcano Arsia Mons on Mars have been mapped to analyse their spatial pattern and to conclude about their formation. For the mapping, high resolution satellite data gathered during the Mars Express mission were used. The spatial distribution of the pit craters was then compared with typical patterns of magmatic sheet intrusions within volcanoes as they are known from Earth. The results show that the pattern of the mapped pit craters and pit crater chains are in good agreement with these sheet intrusions and are therefore likely related to Martian sheet intrusions.Kollapskratrar och kraterkedjor relaterade till vulkanen Arsia Mons på Mars har karterats för att analysera deras spatiala mönster och för att komma till slutsatser för deras tillblivelse. Högupplösta satellitbilder tagna av Mars Express-sonden har använts för karteringen. Fördelningen av de karterade kraterkedjorna jämfördes med typiska fördelningar av magmatiska gångbergarter från vulkaner på jorden. Resultaten visar att fördelningen av kollapskratrar och kraterkedjor överensstämmer enligt förväntningarna och påvisar en relation mellan kollapskratrar och magmatiska gångbergarter på Mars.
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Clavero, Jorge Eduardo. "Evolution of Parinacota volcano and Taapaca Volcanic Complex, Central Andes of Northern Chile." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393075.
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B, Jhon Macario Londoño. "A seismic model for the volcanic activity of Nevado del Ruiz Volcano, Colombia." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149994.
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Erwin, Patrick Seumas. "Palaeomagnetic investigations of volcano instability." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249474.
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Carrier, Aurore. "Endommagement et processus non-linéaires au sein d'un édifice volcanique pressurisé." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAU013/document.
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Sur les volcans on enregistre fréquemment des accélérations du nombre cumulé de séismes et parfois du déplacement de la surface dans les heures, les jours ou les semaines précédant les éruptions. Expliquer une accélération du déplacement de surface par l'utilisation de modèles élastiques linéaires pour les édifices implique d'introduire une accélération de la pressurisation du réservoir et de la base du conduit magmatique avec des temps caractéristiques courts, ce qui est peu réaliste. Une autre voie de recherche consiste à considérer qu'une éruption est due à la rupture du réservoir magmatique, et que cette rupture n'est pas instantanée - elle peut être précédée par une phase d'endommagement progressif de l'édifice, pendant laquelle de petites ruptures ont lieu dans l'édifice. Ces ruptures provoquent l'affaiblissement des modules élastiques de l'édifice. Nous avons examiné l'effet que peut avoir l'affaiblissement des modules élastiques sur le déplacement de surface, ainsi que sur la pression dans le réservoir et le débit de magma entrant. Pour cela nous avons d'abord recherché une loi d'endommagement qui permette d'ajuster les déplacements de surface enregistrés en utilisant le nombre cumulé de séismes. La loi trouvée est une loi puissance d'un paramètre d'endommagement incrémental, qui est le rapport entre la longueur de rupture incrémentale caractéristique et la longueur à rompre pour obtenir une éruption. Cette loi fait intervenir, à l'exposant, le nombre cumulé de séismes.Ce modèle permet d'expliquer des vitesses et des accélérations du déplacement aussi bien faibles que fortes, selon la valeur prise par le paramètre d'endommagement, ainsi que la bifurcation entre un état stable de l'édifice, et un état instable qui mène à l'éruption. L'affaiblissement de l'édifice induit une diminution de la surpression et une accélération du déplacement de surface, la surpression diminuant plus lentement que les modules élastiques du fait de l'approvisionnement du réservoir en magma.Ce modèle peut expliquer une large gamme de comportements pré-éruptifs et éruptifs dans les volcans. Il permet d'ajuster simplement aussi bien les accélérations du déplacement de surface enregistré par les stations GPS sommitales du Piton de la Fournaise pour l'éruption du 30/03/2007, que les déplacements croissants de façon stationnaire du volcan Grimsvötn (Islande), entre 2005 et 2011. Il peut aussi être utilisé pour comprendre les comportements éruptifs plus complexes, comme dans le cas de l'éruption de 2010 du Mérapi (Indonésie). La valeur de la constante de temps du système d'approvisionnement contrôle le décalage temporel entre le maximum de l'endommagement (fin de la crise sismique volcano-tectonique) et le maximum de la déformation ou du flux de magma et donc la dynamique du processus. Une analyse préliminaire montre que le rapport entre les constantes de temps d'affaiblissement de la résistance et de la pression est un facteur de contrôle de la dynamique du processus pré-éruptif et éruptif.L'endommagement d'un édifice volcanique ne peut continuer indéfiniment, cela interdirait le stockage de magma dans l'édifice à long terme. L'édifice volcanique connait donc nécessairement des phases de consolidation. Une première approche d'étude de la consolidation reposant sur l'utilisation d'un critère basé sur les variations relatives de volume a été investiguée. Les résultats montrent cependant qu'une telle approche n'est pas suffisante pour expliquer la nécessaire augmentation des modules élastiques, et que les processus de consolidation chimique sans variation de volume doivent avoir une importance fondamentale dans l'existence de cycles éruptifs. Pour étudier ces processus, il faut disposer d'une observable géophysique indépendante du déplacement de surface - nous proposons d'utiliser l'anisotropie de propagation des ondes de cisaillement dans l'édifice volcanique. Ces variations de résistance de l'édifice peuvent contrôler la pression en profondeurOn volcanoes accelerations of the cumulated number of earthquakes and sometimes of the surface displacement occur in the hours, days and weeks preceding the eruptions. Explaining an acceleration of surface displacement using an elastic model for the volcanic edifice implies an acceleration of the pressure increase in the magma reservoir and in the mantle, at the base of the magma conduit, at short timescales, that is not realistic. Another direction for research consists in considering that an eruption is due to the rupture of the magma reservoir, and that this rupture is not instantaneous - it can be preceded by progressive damage of the edifice, during which low-magnitude earthquakes occur. These ruptures provoke the progressive weakening of the edifice elastic moduli. In this work we have inverstigated the effect of this weakening on the surface displacements, on the reservoir pressure and on the magma flow. We have first searched for a damage law allowing fitting the measured surface displacements by using the cumulated number of recorded earthquakes. The law allowing this fit is a power-law of the incremental damage parameter, with the cumulated number of earthquakes at the exponent. This incremental damage parameter is the ratio between the characteristic incremental rupture length and the length to be ruptured for the eruption.This model allows us to explain weak and strong rates and accelerations of the surface displacement, with the value of the damage parameter. Bifurcation that occurs between a stable state of the edifice and an instable state leading to an eruption is also explained. The weakening of the edifice induces simultaneously a diminution of the reservoir overpressure and an acceleration of the surface displacement, overpressure decreasing more slowly than the elastic moduli, due to the magma feeding of the reservoir.This type of model can explain a wide range of pre-eruptive and eruptive behaviours on volcanoes. It allows the fitting of surface displacement accelerations recorded at the GPS summit stations of Piton de la Fournaise volcano for the March 30th, 2007 eruption, and explains the steady increase of the surface displacement recorded at the summit of Grimsvötn volcano (Iceland), between 2005 and 2011. It may be used for understanding the complex eruptive behaviours, comprising multiple episodes, as in the case of the October-November 2010 eruption of the Merapi volcano (Indonesia). The value of the characteristic time of the feeding system controls the time delay between the maximum of damage (end of the volcano-tectonic seismic crisis) and the maximum of the surface displacement or magma flow. A preliminary analysis shows that the ratio between the weakening characteristic times of the edifice strength and reservoir pressure participate to the control of the pre-eruptive and eruptive process dynamics.Damage of the volcanic edifice can not continue indefinitely, otherwise long-term magma storage would be impossible in the volcanic edifice. The volcanic edifice therefore necessarily experiments periods of strenghtening. A first approach for studying this strengthening relying on a criterion based on the volume relative variation of the edifice has been investigated. Results show that this approach is not sufficient to explain the necessary increase of the elastic moduli. Chemical strenghtening processes without volume changes should have a fundamental role in the existence of eruptive cycles. For improving our knowledge of these processes, we need a further geophysical observable, independent on the surface displacements - we propose to use shear-wave anisotropy in the volcanic edifice.We finally show that the surface dynamics imposed by strength changes of the edifice can influence the dynamics of the deep processes, and consider the possibility of a retroaction of the edifice strength changes on the deep source processes
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Picquout, Adrien. "Impacts géographiques de l'éruption de 2010 du volcan Merapi, Java, Indonésie." Thesis, Paris 1, 2013. http://www.theses.fr/2013PA010581/document.
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Le 26 octobre 2010, le Merapi, volcan le plus peuplé et le plus actif de l'île de Java en Indonésie, est entré en éruption. Depuis plusieurs mois, l'activité du volcan avait crû de manière exponentielle et les scientifiques s'attendaient à une éruption exceptionnelle. Leurs pronostics furent confirmés puisqu'un blast parcourut une distance de 8 km, rasa en partie deux villages évacués, et tua mbah Marijan, le « gardien des clés du volcan » et son entourage, ce qui perturba l'équilibre culturel de la région. Dans les jours suivants, l'activité du volcan continua de s'intensifier et des évacuations massives furent organisées. L'éruption paroxysmale du Merapi eut lieu dans la nuit du 4 au 5 novembre ; alors que plusieurs dizaines de milliers de villageois étaient en train de fuir le volcan, de puissantes coulées pyroclastiques dévastèrent les flancs du volcan, tuant et détruisant tout sur leur passage sur une distance maximale de 17 km. Cette nuit-là, plus de 250 personnes furent tuées et des milliers d'autres blessées. Le secteur agricole subit de lourdes pertes puisque de nombreuses récoltes et un grand nombre de têtes de bétail furent perdus. L'activité touristique de la région connut une réaction en chaîne d'impacts, générée en grande partie par la fermeture de l'aéroport de Yogyakarta. La thèse propose de faire une étude transversale et systémique de ces impacts en analysant comment gouvernement et populations se remettent de cette éruption et s'apprêtent à faire face à une future crise causée par le MerapiOn October 26th 2010, the Merapi volcano, the most populated and active volcano on the Java Island in Indonesia, began erupting. During several months, the volcano's activity grew exponentially and scientists were expecting an exceptional eruption. Their predictions got confirmed as a blast ran through a distance of 8 km, partially destructed two villages (that got evacuated) and killed mbah Marijan, the « Volcano's keys guardian » and his entourage. As a consequence, the cultural balance of the region got disrupted for a while. In the following days, the volcano's activity kept increasing and mass evacuations were organized. The paroxysmal eruption of Merapi occurred in the night of November 4th to 5th 2010, while tens of thousands of villagers were running away from the volcano. Powerful pyroclastic flows ran down its flanks, killing and destroying everything on their way over a maximum distance of 17 km. During that night, over 250 people were killed and thousands were injured. The agricultural sector suffered from heavy losses as many crops and livestock were lost. The tourism industry in the region experienced a chain reaction of impacts generated by the closure of Yogyakarta airport. The thesis offers to make a transversal and systemic study of these impacts by analyzing how the government and people recovered from the eruption and how they are to face a future crisis caused by the Merapi
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Sadikin, Nurlia. "Volcano-tectonic Earthquakes and Magma Supply System at Guntur Volcano, with Long-term Dormant Period." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124353.
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Auer, Sara Lynn. "Diverse oxygen isotope values and high magmatic water contents within the volcanic record of Klyuschevskoy Volcano, Kamchatka, Russia /." Connect to title online (Scholars' Bank), 2007. http://handle.net/1794/6054.
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Beachly, Matthew William 1986. "The Upper Crustal P-wave Velocity Structure of Newberry Volcano, Central Oregon." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11475.
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xii, 98 p. : ill. (some col.)The upper-crustal seismic-velocity structure of Newberry volcano, central Oregon, is imaged using P-wave travel time tomography. The inversion combines a densely-spaced seismic line collected in 2008 with two USGS seismic experiments from the 1980s. A high-velocity ring (7 km EW by 5 km NS) beneath the inner caldera faults suggests an intrusive ring complex 200 to 500 m thick. Within this ring shallow low velocities (<2 km depth) are interpreted as caldera fill and a subsided block. High velocities below 2 km depth could be intrusive complexes. There appears to be a low-velocity body at 3-6 km depth beneath the center of the volcano. This region is poorly resolved in the inversion because the ray paths bend around the low-velocity body. The 2008 data also recorded a secondary arrival that may be a delayed P-wave interacting with the low-velocity body.
Committee in charge: Emilie E.E. Hooft, Chairperson; Douglas R. Toomey, Member; Katharine V. Cashman, Member
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Toombs, Andrew Charles. "Volcano-tectonic deformation and lava flow subsidence modelling using InSAR data at Nyamuragira Volcano, D.R. Congo." Thesis, University of Reading, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.553002.
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The rift volcano Nyamuragira in D.R. Congo regularly produces large- volume lava flows resulting from flank fissure eruptions. The eruptions are usually fed by near-vertical dykes whose orientation and location are controlled by local and regional stress. Fissuring occasionally occurs within the summit caldera, but dyke emplacement and fissuring is usually confined to the flanks along preferential zones of weakness which radiate away from the 2 x 2.2 km caldera. Space-borne Synthetic Aperture Radar Interferometry (InSAR) was used to measure eo-eruptive and inter-eruptive surface deformation at the volcano between 1996 and 2010 (8 eruptions). The largest line-of-sight (LOS) displacement due to dyke emplacement (42 cm) was recorded during the 2002 eruption. Previously unreported displacements have been measured for the 1998, 2001 and 2004 eruptions. Numerical modelling of the 2006 and 2010 eruptive events was tried. The . orientation and size of the dykes is, however, poorly constrained, and the nature of subsurface connectivity with the caldera is not known. Both dykes were emplaced on the southern flank and are aligned with a NNW-trending fracture zone running between Nyamuragira and nearby Nyiragongo. Two methods using regression analyses on time-series data were devised to model and remove lava flow subsidence signals from interferograms. Subsidence signals> 3cm/year have been measured and are a function of time and lava thickness. Linear rate subsidence models were found to be appropriate for most lava flows. Detailed mapping of the recent lava flows of Nyamuragira has also better constrained their location and spatial extent. By stacking interferograms we obtained mean deformation maps of the volcano revealing inter-eruptive deformation: 1. Uplift within the Eastern Pit Crater and inflation of the summit prior to the 2010 eruption; 2. Post- eruptive deflation centred on the 2010 eruption site; 3. Long-period subsidence beneath the Western Crater and rifring of the caldera and 1 immediate flanks; 4. Long-period subsidence centred on the 2006 eruptive vent thought to be associated with visco-elastic relaxation of a cooling magma body; 5. Similar subsidence fields centred on the 1998 and 2002 eruptive vents; 6. Anomalous subsidence associated with the 1991-93 lava flow; 7. The existence of an apparently stable, fault-bounded, and dyke- resistant block of Precambrian crust beneath the NW flank of the volcano, probably related to the Western Border Fault.
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Calvari, Sonia. "Hazard assessment on Etna volcano, Italy." Thesis, Lancaster University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301816.
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Zhang, Yan. "Wireless sensor network for volcano monitoring." Thesis, KTH, Mikroelektronik och Informationsteknik, IMIT, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92301.
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The monitoring of volcanoes for risk assessment has deployed single sensors for years. This kind of system requires manual supervision to monitor each sensor, which makes the monitoring work not flexible and efficient enough to adapt to variable volcano environments. With the development of wireless sensor networks, the accuracy and coverage of volcano observations can be improved by deploying networked sensors. This paper proposes a wireless sensor network prototype for volcano remote monitoring, which was built and tested in a field campaign in volcano Etna, Italy in September of 2004.Hardware design of sensors, in-depth sensor network design and software module architecture will be introduced in this paper. The experience gained from the practical work in volcano Etna will be used in an upcoming volcano monitoring project.Vulkaner har, i syfte för riskuppskattning, under en lång tid observerats med enkel sensorteknik.Det systemet behöver dock manuell övervakning av varje sensor, vilket gör att övervakningssystemet inte blir nog flexibelt eller effektivt för att kunna anpassas till en variabel vulkanmiljö. Med utvecklingen av trådlösa sensornätverk kan noggrannheten och täckningen av vulkanövervakning förbättras. I denna rapport föreslås en prototyp för ett trådlöst sensornätverk avsett för övervakning av vulkaner.Denna prototyp byggdes och provades i en fältkampanj på vulkanen Etna i september 2004. I denna rapport presenteras även hårdvarudesign av sensorer, fördjupad design av sensornätverket och arkitektur av mjukvarumoduler.Erfarenheten från det praktiska arbetet på Etna kommer att användas i ett kommande vulkanprojekt.
数年耒， 火山庐盎'情予页手贝哑工儡乍中普遍采用的是单传感器系茎充。 这手中系彗充需要人工监控每个传 感器, 由于其不可多灵活高效, 不苜旨适应多变的火山壬不土竞。 随着无线传感器网络的岌展, 采用 网络互连的传感器苜旨句多提高火山监暑贝畦的子崔确'性养口宗置盖范围o 本文提出了一茉中用于火山远程监 控的无线传感器网络原型, 在 2口口4年 日 月薏犬禾lj士矣特男B火山的科学考察活动中, i亥网络芋皮搭 建井寄贝哑试应用。 本文轧寻介妻召宝亥网络中的传感器的丑更儡牛设元十, 传感器网络设无十以及软儡牛摸块结 构。 在士矣特丑B火山的实地考禀工儡乍中获宁导的宝贵经验耳幂儡故为下一唇介段火山监手贝哑项目的守旨南。
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Palacios, Pablo Bolívar Palacios. "Seismo-acoustics of Tungurahua Volcano, Ecuador." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702151.
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Explosive volcanic eruptions produce seismic and acoustic waves that travel through the ground and air, respectively, interacting at the air-ground boundary. This thesis presents a study of these signals and how they correlate during five sustained eruptions at Tungurahua volcano, Ecuador. It is well known that corrections for site effects can be necessary in the study of seismic sources. What is less well known is that acoustic waves, after coupling at the air-ground interface, are also sensitive to site effects, thereby influencing seismic records. In this study a new procedure for site effect corrections that uses seismic noise is developed and it is shown that seismic source locations improve after applying such corrections. From acoustic studies about jets, it is well known that the acoustic intensity recorded at a fixed location depends on the jet velocity. Here, it is proposed that the seismic intensities of waves produced during sustained eruptions depend on the flow velocity of the gas-pyroclast mixture that is ejected through the conduit, which forms the volcanic plume and generates the acoustic waves. Additionally, seismic and an acoustic indices are defined and it is observed that such indices correlate during paroxysmal eruptions. As a consequence, a significant conclusion is that during paroxysms both the seismic and acoustic source type must necessarily be the same, and likely dipolar, or at least their dipolar components must be dominant in the near field. Seismic tremor locations for the five eruptions studied form clusters, in approximately the same region, beneath the northwestern flank of the volcano. As cluster location does not change significantly through time, it can be concluded that variations in seismic and acoustic intensities are due to variations in eruptive size rather than variations in source-station distance. A measure of the 'eruption seismic size' and 'eruption acoustic size' are defined as the cumulative intensities at a given station, and used to compare the eruptions. It is observed that the eruption seismic size correlates with the plume heights that they produced. The seismic and acoustic indices presented here offer insights into volcanic processes associated with paroxysmal eruptions. Furthermore, the monitoring of such indices improves the real time hazard assessment, being particularly useful in explosive sustained eruptions.
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Aliotta, Marco Antonio. "Data mining techniques on volcano monitoring." Doctoral thesis, Università di Catania, 2013. http://hdl.handle.net/10761/1364.
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The aim of this thesis is the study of data mining process able to discover implicit information from huge amount of data. In particular, indexing of datasets is studied to speed the efficiency of search algorithm. All of the presented techniques are applied in geophysical research field where the huge amount of data hide implicit information related to volcanic processes and their evolution over time. Data mining techniques, reported in details in the next chapters, are implemented with the aim of recurrent patterns analysis from heterogeneous data.
This thesis is organized as follows. Chapter 1 introduces the problem of searching in a metric space, showing the key applications (from text retrieval to computational biology and so on) and the basic concepts (e.g. metric distance function). The current solutions, together with a model for standardization, are presented in Chapter 2. A novel indexing structure, the K-Pole Tree, that uses a dynamic number of pivots to partition a metric space, is presented in Chapter 3, after a taxonomy of the state-of-the-art indexing algorithm. Experimental effectiveness of K-Pole Tree is compared to other efficient algorithms in Chapter 4, where proximity queries results are showed. In Chapter 5 a basic review of pattern recognition techniques is reported. In particular, DBSCAN Algorithm and SVM (Support Vector Machines) are discussed. Finally, Chapter 6 shows some geophysical applications where data mining techniques are applied for volcano data analysis and surveillance purpose. In particular, an application for clustering infrasound signals and another to index an thermal image database are presented.
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Phillips, Kathleen A. "Using seafloor geodesy to monitor volcanic collapse on the south flank of Kilauea Volcano, Hawaii." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3208095.
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Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed May 22, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 124-129).
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Alatorre, Ibargüengoitia Miguel Angel. "A model of volcanic explosions at Popocatépetl volcano (Mexico): Integrating fragmentation experiments and ballistic analysis." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-134097.
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Powell, Tanya Wendy. "Characterisation of volcano-seismic events and their relation to volcanic processes in the Montserrat eruption." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417741.
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CorteÌs, JoaquiÌn Alberto. "Thermodynamics of magma recharge in open volcanic systems : a case study from Stromboli volcano, Italy." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421973.
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Vallejo, Vargas Silvia Ximena. "Numerical models of volcanic flows for an estimation and delimitation of volcanic hazards, the case of Reventador volcano (Ecuador)." Thesis, Université Clermont Auvergne (2017-2020), 2017. http://www.theses.fr/2017CLFAC100/document.
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Les coulées de laves sont les produits volcaniques les plus représentatifs des éruptions effusives. Elles sont formées quand le magma est extrudé et se répand à la surface de la Terre. Quand la lave arrive en surface, elle perd de la chaleur et refroidit. Le refroidissement affecte directement les propriétés rhéologiques de la lave, jusqu’à arrêter son écoulement. Les paramètres rhéologiques qui contrôlent la dynamique des coulées de laves sont la viscosité et le seuil de plasticité, qui dépendent eux-mêmes de la composition chimique, de la cristallinité et de la teneur en bulles. Il existe de nombreux modèles d’estimation de la rhéologie, la plupart développés pour les coulées de lave basaltiques et quelque uns pour les coulées de lave andésitiques. Les coulées de laves peuvent grandement affecter les régions peuplées, les infrastructures et l’environnement. Un moyen de prévoir les futurs dégâts est de développer des modèles numériques pour prévoir la propagation des coulées de laves sur des topographies volcaniques réelles. Cette méthode difficile combine la topographie, la rhéologie, la perte de chaleur et la dynamique de l’écoulement pour simuler l’emplacement d’une coulée de lave précise. Le code numérique VolcFlow, qui est basé sur une approche moyennée verticale, est capable de reproduire les caractéristiques principales des dépôts comme la morphologie, la longueur et l’épaisseur. Dans cette étude sont proposés trois modèles implémentés dans VolcFlow et ayant pour but de simuler des coulées de laves. Le premier est isotherme, le deuxième inclut le refroidissement et les variations rhéologiques associées, et le troisième prend en considération la déformation de la croûte à la surface de la coulée et son effet sur l’emplacement de la coulée. Afin de vérifier la validité des différentes approches, les modèles sont testés sur quatre cas d’étude : deux coulées de lave de composition basaltique (expérience de basalte fondu de Syracuse lava Project et la coulée de lave d’août novembre 2015 du Piton de la Fournaise, France) et deux de compositions andésitique (la coulée de lave du 4-5 décembre 2015 du Tungurahua et trois coulées de lave du Reventador, Equateur). Les résultats des simulations montrent que le modèle isotherme peut reproduire les coulées même s’il ne prend pas en compte les variations de rhéologie et le refroidissement. Le modèle incluant la cristallisation, induite par le refroidissement de la lave au cours de son écoulement, et les variations rhéologiques associées donne de très bons résultats mais est très sensible aux paramètres d’entrée, en particulier à la viscosité, elle-même très dépendante de la composition chimique et de la température. Enfin, le modèle prenant en compte le refroidissement et les variations de rhéologie par une loi synthétique sigmoïde montre une bonne cohérence dans tous les cas simulés, sauf pour le Piton de la Fournaise. Le modèle visant à simuler la formation d’une croûte à la surface de la lave et sa percée par l’écoulement sous-jacent amène uniquement à l’épaississement de la croûte. Le mécanisme de percée n’est pas reproduit avec VolcFlowLava flows are the most representative volcanic products of effusive eruptions and are formed whenthe magma is extruded and flows on the surface. When lava flows reach the surface they lose heat and cool.Cooling affects directly the rheology of the lava up to a point where it cannot flow anymore. Rheologicalparameters that control the dynamics of lava flows are the viscosity and the yield strength which in turndepends on the chemical composition, crystallinity and bubble content. There exist numerous models forthe rheology estimation, mostly developed for basaltic lava flows and few for andesitic ones.Lava flows can highly affect populated areas, infrastructures and environment. A way to forecastthe future damages is to developed numerical codes of the lava propagation on real volcanic topography.This challenging method combines the topography, the rheology, the heat loss, and flow dynamics tosimulate the emplacement of a particular lava flow. The numerical code VolcFlow which is based on thedepth-averaged approach is able to reproduce the main physical characteristics of the deposits likemorphology, length and thickness. Here 3 models are proposed for their implementation in VolcFlow withthe aim to simulate lava flows. One model is isothermal, the second includes cooling and the associatedrheological variations, and the third takes into account the crust formation and its effect on the flowemplacement. To check the validity of the different approaches, the models were tested with four studycases, two with basaltic compositions (molten basalt experiment of the Syracuse lava Project and the August-November, 2015 lava flow from Piton de la Fournaise, France) and two with andesitic compositions (theDecember 4th-5th lava flow from Tungurahua, Ecuador, and three lava flows from El Reventador,Ecuador). Results of the simulations shows that the isothermal model can reproduce the flows even if itdoes not consider the cooling and rheology variation. The model that includes rheological laws as functionof crystallization induced by cooling down flow can give very good results but is very sensitive to the inputdata, in particular to the fluid viscosity that is very dependent on chemical composition and temperature.Finally, the model that includes cooling and synthetic sigmoid rheological law shows good coherence for allthe cases except at Piton de la Fournaise. The model that aims to simulate the formation of a crust on thelava flow surface, lava flowing underneath and break-out mechanisms leads to the thickening of the crust.Hence, break-out mechanism is not reproduced with VolcFlow
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Janssen, Volker Surveying & Spatial Information Systems Faculty of Engineering UNSW. "A mixed-mode GPS network processing approach for volcano deformation monitoring." Awarded by:University of New South Wales. School of Surveying and Spatial Information Systems, 2003. http://handle.unsw.edu.au/1959.4/20771.
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Ground deformation due to volcanic magma intrusion is recognised as an important precursor of eruptive activity at a volcano. The Global Positioning System (GPS) is ideally suited for this application by being able to measure three-dimensional coordinate changes of the monitoring points over time. Due to the highly disturbed ionosphere in equatorial regions, particularly during times of maximum solar activity, a deformation monitoring network consisting entirely of single-frequency GPS receivers cannot deliver baseline solutions at the desired accuracy level. In this thesis, a mixed-mode GPS network approach is proposed in order to optimise the existing continuous single-frequency deformation monitoring system on the Papandayan volcano in West Java, Indonesia. A sparse network of dual-frequency GPS receivers surrounding the deformation zone is used to generate empirical 'correction terms' in order to model the regional ionosphere. These corrections are then applied to the single-frequency data of the inner network to improve the accuracy of the results by modelling the residual atmospheric biases that would otherwise be neglected. This thesis reviews the characteristics of existing continuously operating GPS deformation monitoring networks. The UNSW-designed mixed-mode GPS-based volcano deformation monitoring system and the adopted data processing strategy are described, and details of the system's deployment in an inhospitable volcanic environment are given. A method to optimise the number of observations for deformation monitoring networks where the deforming body itself blocks out part of the sky, and thereby significantly reduces the number of GPS satellites being tracked, is presented. The ionosphere and its effects on GPS signals, with special consideration for the situation in equatorial regions, are characterised. The nature of the empirically-derived 'correction terms' is investigated by using several data sets collected over different baseline lengths, at various geographical locations, and under different ionospheric conditions. Data from a range of GPS networks of various sizes, located at different geomagnetic latitudes, including data collected on Gunung Papandayan, were processed to test the feasibility of the proposed mixed-mode deformation monitoring network approach. It was found that GPS baseline results can be improved by up to 50% in the midlatitude region when the 'correction terms' are applied, although the performance of the system degrades in close proximity to the geomagnetic equator during a solar maximum.
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Roberts, Katie Sarah. "Mud volcano systems : structure, evolution and processes." Thesis, Durham University, 2011. http://etheses.dur.ac.uk/752/.
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Mud volcano systems erupt sediment and fluid onto the Earth’s surface producing edifices up to 25 km3 in volume however, little is known about how such volumes are transported through the Earth’s crust. This thesis investigates whether transport is through mud-dyke-sill complexes, or is diapiric. Structural field mapping of exhumed mud volcano intrusive domains onshore in Azerbaijan, shows that feeder complexes are 200-800 m wide and roughly circular. These complexes consist of various fracture networks and a megabreccia of country rock blocks tens-of-metres-across that have rotated up to 90° in a matrix of mud. A structural domain model categorises regions within the feeder complex which formed during stoping processes. Structural mapping is combined with nearest neighbour and 2-point-azimuth statistical analysis of vent distributions described from nine mud volcanoes in Azerbaijan and Lusi mud volcano, East Java. Vent distributions are non-random, showing alignments with: 1) anticline crestal faulting, 2) fractures 3) ring faults, and 4) detachment faults indicating that fracture systems and regional stresses significantly influence feeder complex architecture. Lusi’s vent alignments change orientation from 2006-2010 implying regions 10 km east and west of the main vent are more likely to be impacted by new vents due to the onset of elongate-caldera collapse. Kilometre-scale, elongate scarps are identified as ‘sector collapses’ on mud volcanoes in Azerbaijan due to morphological similarity to those on igneous volcanoes. Shape parameters distinguish sector collapses and eruptive mud breccia flows allowing identification in field and satellite-based mapping. The updip domains are characterised by vents showing there is linkage to deeper mud volcano fluid flow pathways. A model of a deflating mud chamber triggering ‘thin-skinned’ sector collapse is proposed. This sector collapse model, vent alignment orientation analysis and intrusive domain structural model are ultimately integrated into a comprehensive schematic model of the mud volcano system.
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Bracamontes, Dulce Maria Vargas. "Stress models related to volcano-tectonic earthquakes." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540585.
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Skilling, Ian Paul. "The geological evolution of Suswa volcano, Kenya." Thesis, Lancaster University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261744.
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Dabrowa, Amy Louise. "Volcano infrasound : from laboratory to global scale." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.684649.
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Volcanic infrasound is detectable at distances up to 10,000 km from the source and increasingly commonly, volcanoes are monitored at local distances using infrasound. As a relatively new area of research, many avenues can be explored to improve techniques for monitoring and interpreting infrasound and a range of approaches are utilised in this thesis. A database was compiled of 110 events at 36 globally distributed volcanoes. Infrasound from these events was searched for and characterised using data from infrasound arrays of the International Monitoring System (IMS) to assess how the IMS could be used to monitor remote volcanoes. The distance at which volcanic events were detected increased with eruption plume height. Amplitude decay rates varied widely, but an amplitude decay rate of l/r (where r is distance to source) was successfully used to compare eruptions. The amplitude and energy of volcanic infrasound was found to increase with plume height, whilst frequency decreased. These characteristics allow a broad estimation of eruption intensity using long-range infrasound data from the IMS alone, and in combination with simple event location methodologies demonstrate how the IMS could be used to monitor remote volcanoes. Infrasound from Mount Erebus, Antarctica, is regularly detected at an infrasound array 25 km distant. Comparing these data with that recorded near the vent allowed study of infrasound propagation effects, and investigation of how volcanoes could be monitored at this distance. The rate of amplitude decay observed between near-vent sensors and an infrasound array 25 km from the vent was greater than expected by purely hemispherical spreading. Decay rates varied between just less than l/r and approaching 1/r2 over the course of just a few days, indicating that varying meteorological conditions are likely to have a strong effect. Of the known infrasound signals, 75% were detected at IS55 and methodology was successfully developed to automatically detect further events. This demonstrates that although the true amplitude of volcanic events would be unknown due to varying amplitude decay rates, volcanoes could still be successfully monitored at this distance in terms of the frequency of occurrence of events. A set of analogue experiments were conducted to offer insights into the processes that may be important during infrasound production at Strombolian eruptions and other similar volcanic events. Bubbles burst at an air-liquid interface whilst being recorded by a pair of microphones and a high speed camera to investigate the effect of bubble volume, fluid viscosity and rupture dynamics. The experimental system exhibited complex behaviour. Sound began concurrently with bubble rupture and varied greatly with radial position around the source exhibiting dipole characteristics. Both acoustic and rupture characteristics; amplitude, frequency and bubble rupture speeds all increase with decreasing viscosity. Audio results are most closely reproduced by a simple model which assumes that the sound produced is due to excitation of the atmosphere by directional mass flow from the bubble.
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Williams-Jones, Glyn. "Integrated geophysical studies at Masaya volcano, Nicaragua." Thesis, Open University, 2001. http://oro.open.ac.uk/54428/.
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Research into the mechanisms responsible for the lasting, cyclic activity at Masaya volcano can lead to a better understanding of persistently degassing volcanoes. This study is greatly enhanced by the integration of dynamic micro-gravity, deformation and gas flux measurements. The acquisition of extended temporal and spatial geophysical data will also allow for the development of robust models for the dynamics of magmatic systems. Masaya volcano, Nicaragua, is one of the most active systems in Central America, making it an excellent natural laboratory for this study. It is noted for repeated episodes of lava lake formation, strong degassing and subsequent quiescence. Ground-based geophysical measurements show two episodes of similar magnitude gravity decreases in 1993-1994 and 1997-1999, separated by a period of minor gravity increase. A major increase in S02 gas flux from 1997-1999 correlates well with the most recent episode of gravity decrease. The gravity changes are not accompanied by deformation in the summit areas and are interpreted in terms of sub-surface density changes. The persistent degassing at Masaya suggests that up to -15 krrr' of magma may have degassed over the last 150 years, only a minute fraction of which has been erupted. Furthermore, thermal flux calculations suggest that 0.5 krrr' of magma (the estimated volume of the shallow reservoir) would cool from liquidus to just above solidus temperatures in only 5 years. The high rates of degassing and cooling at open-system volcanoes such as Masaya raise questions as to the ultimate fate of this degassed and cooled magma. A number of models have been proposed to explain this, but the most likely mechanism to explain persistent activity at Masaya and other similar volcanoes is convective removal of cooled and degassed magma and subsequent recharge by volatile-rich magma from depth. Another fundamental question in modem volcanology concerns the manner in which a volcanic eruption is triggered; the intrusion of fresh magma into a reservoir is thought to be a key component. The amount by which previously ponded reservoir magma interacts with a newly intruded magma will determine the nature and rate of eruption as well as the chemistry of erupted lavas and shallow dykes. The physics of this interaction can be investigated through a conventional monitoring procedure that incorporates the Mogi model relating ground deformation (~) to changes in volume of a magma reservoir. Gravity changes (.1.g)combined with ground deformation provides information on magma reservoir mass changes. Models developed here predict how, during inflation, the observed .1.gI~ gradient will evolve as a volcano develops from a state of dormancy through unrest into a state of explosive activity.
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Setiawan, Ari. "Modeling of Gravity Changes on Merapi Volcano." Phd thesis, [S.l. : s.n.], 2003. https://tuprints.ulb.tu-darmstadt.de/362/17/cv.pdf.
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Merapi volcano, located in Central Java, is one of the most active volcanoes in Indonesia. 2 million people are living in its immediate neighborhood. Therefore Merapi was selected within the International Decade of Natural Disaster Reduction (IDNDR) of UNESCO as one of 15 so called high risk volcanoes in the world. National and International research groups from Indonesia, France, Netherlands, Japan, USA and Germany are working on Merapi. Different methods are applied on Merapi to study the volcanic processes and to improve the possibilities to predict future eruptions. In this thesis the importance of gravity changes in space and time for the analysis of volcanic processes is analyzed and further developed. First the basic theory of Earth's gravity field and gravity anomalies is described. For the interpretation of gravity anomalies several programs have been developed using the MATLAB software package. The programs are used for the interpretation of gravity changes in time which have been observed five times between summer 1997 and summer 2000 in a repetition network around Merapi volcano. This network consists of 23 stations. During all campaigns four LaCoste&Romberg gravimeters model G and D have been used. Height changes at the observation sites are controlled by GPS-observations which have been carried out in parallel with the gravity measurements. The observed gravity and height changes are small. They reveal that Merapi volcano is just now an open system where no large stresses can build up. Nevertheless possible models are developed to explain the observed changes. Based on four geometric models of magma chamber and conduit within the volcano?s edifice as found in the literature the migration of magma in the conduit is investigated. The conduit system thereby is modeled by a cylinder, the magma chamber by a sphere. It is shown, that gravity changes map the migration of the magma, if gravity changes at stations at the crater rim are considered. Gravity changes at stations far away from the volcano conduit (2 ? 25 km) can be explained by changes within the geohydrothermal system. For this purpose particular ground water layers as determined by other geophysical methods (resistivity observations, magnetotelluric measurements and LOTEM) are modeled as concentric cylinders around the conduit of Merapi volcano. The resulting density changes in the cylinders explain with sufficient accuracy the observed gravity changes. Precise repeated gravity observations in combination with other geophysical methods allow therefore the detailed analysis of subsurface mass migration within a volcano.
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Montgomery-Brown, Emily Kvietka Desmarais. "Time dependent deformation of Kīlauea Volcano, Hawaii /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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