Dissertations / Theses on the topic 'Chile Earthquake'

A lack of comprehensive understanding of the seismic hazards associated with a subduction zone can lead to inadequate anticipation of earthquakes and tsunami magnitudes. Four hundred and fifty years of Chilean historical documents record the effects of numerous great earthquakes; however, with recurrence intervals between the largest megathrust earthquakes approaching 300 years, seismic hazard assessment requires longer chronologies. This thesis seeks to verify and extend historical records in south central Chile using a relative sea-level approach to palaeoseismology, developed in Alaska and the Pacific Northwest. Quantitative, diatom-based approaches to relative sea-level reconstruction are successful in reconstructing the magnitude of coseismic deformation during recent, well documented Chilean earthquakes. Disparities between my estimates and independent data highlight the possibility of shaking-induced sediment consolidation of tidal marshes. Following this encouraging confirmation of the approach, I quantify land-level changes in longer sedimentary records from the centre of the 1960 rupture zone. Here, laterally extensive marsh soils abruptly overlain by low intertidal sediments attest to the occurrence of four megathrust earthquakes. Field sites preserve evidence of the 1960 and 1575 earthquakes and Bayesian age-depth modelling constrains the timing of two predecessors to 1270 to 1410 and 1050 to 1200. The sediments and biostratigraphy lack evidence for the historically documented 1737 and 1837 earthquakes. The distribution of documented effects of these ruptures and the new palaeoseismic data presented in this thesis suggests these earthquakes were smaller in magnitude and located in the southern portion of the 1960 rupture segment, as other authors have previously inferred. Coastal sediments record relative sea-level changes reflecting both the earthquake deformation cycle and non-seismic processes. The 1000 year record of net relative sea-level rise implied by the new records presented here differs from the mid to late Holocene relative sea-level fall inferred from previous field studies and modelling approaches.

No Chile, país de terremotos, a surpresa foi total quando multitudinários saques a estabelecimentos comerciais começaram logo depois do megassismo que atingiu, na madrugada de sábado 27 de fevereiro de 2010, Concepción, a terceira maior área metropolitana do país. Organizaram-se nos bairros estratégias de autodefesa por temor aos rumores sobre a chegada de saqueadores. Para se restabelecer a ordem social, foi decretado Estado de Exceção. Este estudo exploratório e qualitativo busca enxergar a relação entre terremoto, violência coletiva e insegurança urbana com base nos depoimentos de homens e mulheres que entrevistamos em Concepción dois anos depois do cataclismo. Inspirados no debate teórico sobre a memória coletiva, analisaremos os silêncios e olvidos que fazem parte dos testemunhos; assim, iremos interrogar o caráter inédito que os entrevistados, mas também acadêmicos e autoridades, outorgaram aos saques pós-terremoto, que, como iremos ver, foram interpretados como sintoma do deterioramento moral da sociedade chilena sob o regime neoliberal. Por intermédio de diferentes registros do passado, buscaremos rastros sobre conflitos sociais e políticos em outros momentos da história telúrica nacional. Sobre os episódios de 2010 em específico, e seguindo os trabalhos de Charles Tilly e Javier Auyero, apresentamos numa escala microespacial alvos, dinâmicas e repertórios dos saques conforme as rememorações dos consultados, entre eles, donos de lojas vitimizados pela multidão. Por fim, para indagar o deslocamento do medo do terremoto ao medo dos outros, chamaremos a atenção sobre os modos pelos quais são representados diferentes bairros da cidade e o papel dos rumores.
Chileans, a population used to earthquakes, woke up with surprise in the morning of February 27th, 2010 since right after the earthquake that hit Concepción, the third largest metropolitan area in the country, massive looting to stores came about. Fed by rumors about roving mobs, Concepcion residents formed their own neighborhood defense squads to guard their homes, whereas the Chilean government declared State of Exception to restore the social order. Drawing on testimonies of men and women I interviewed in Concepción two years after the disaster, this exploratory and qualitative research examines the relationship between earthquake, collective violence, and urban insecurity. Following a theoretical discussion about collective memories, I explore how silence and forgetting are active elements in the process of collective remembering. In addition, this project analyzes the sense of exceptionality that my interviewees, other scholars, and state authorities have assigned to looting in the aftermath of the earthquake; events that, as I shall demonstrate, were interpreted as a symptom of moral decadence of Chilean society under the neoliberal regime. By scrutinizing historical data about past earthquakes, I look at traces of social and political conflicts associated with the occurrence of natural disaster like the one I describe here. Concerning the 2010 facts, I make use of the framework offered by Charles Tilly and Javier Auyero to present, at a micro-scale level, looting targets, dynamics and repertoires based on narratives collected empirically (among them, testimonies of storeowners who were victimized by the crowd). Finally, to explore the displacement of fearin particular, from the fear to earthquake to the fear of the othersI point out the need to pay attention to the ways in which different neighborhoods are conceived of as well as the role of rumors.

The seismogenic zone of subduction margins has the potential to generate some of the world’s largest earthquakes. A detailed study of the 2010 Mw 8.8 Maule, Chile rupture has enabled interpretation of the controls that govern subduction zone seismic behaviour across the earthquake cycle. In this thesis, we focus on two aspects of the central Chile margin: (1) imaging physical properties in the forearc and along the plate interface; (2) assessing source complexity of megathrust ruptures. We exploit a dataset of seismic body wave onset times from local aftershocks recorded on a temporary network to derive a 3-D seismic velocity model of the Maule rupture area. We image the main domains of the subduction zone and find a high velocity anomaly located along the plate interface, which we initially interpret as a subducted topographic high. We then develop a second, more accurate velocity model that uses an improved arrival time dataset together with observations from ocean-bottom seismometers. This refined model gives a sharper view of both the plate interface close to the trench, and the marine forearc. We show that ancient blocks of dense mantle in the lower forearc may have decelerated slip during the Maule earthquake and contributed to its nucleation. Furthermore, we infer that fluid saturated sediments inhibited significant slip close to the trench. We study source processes of a large aftershock of the Maule sequence, the 2011 Mw 7.1 Araucania earthquake, by inverting local seismic waveforms for a multiple point-source faulting solution. We find this earthquake constituted rupture on the plate interface followed by almost instantaneous slip along a normal fault in the overriding plate: the first observation of its kind. The second rupture of this closely-spaced doublet was hidden from teleseismic faulting solutions, and may have been dynamically triggered by S-waves from the first event. Overall, our work highlights the role played by the upper plate in subduction zone seismogenesis. We suggest that seismic velocities can help to characterise the behaviour of future large megathrust earthquakes. We show that the potential hazard posed by closely-spaced doublets involving the upper plate should be accounted for in real-time tsunami warning systems by using local waveform analysis.

Logging and large earthquakes are disturbances that may significantly affect hydrological and erosional processes and process rates, although in decisively different ways. Despite numerous studies that have documented the impacts of both deforestation and earthquakes on water and sediment fluxes, a number of details regarding the timing and type of de- and reforestation; seismic impacts on subsurface water fluxes; or the overall geomorphic work involved have remained unresolved. The main objective of this thesis is to address these shortcomings and to better understand and compare the hydrological and erosional process responses to such natural and man-made disturbances. To this end, south-central Chile provides an excellent natural laboratory owing to its high seismicity and the ongoing conversion of land into highly productive plantation forests. In this dissertation I combine paired catchment experiments, data analysis techniques, and physics-based modelling to investigate: 1) the effect of plantation forests on water resources, 2) the source and sink behavior of timber harvest areas in terms of overland flow generation and sediment fluxes, 3) geomorphic work and its efficiency as a function of seasonal logging, 4) possible hydrologic responses of the saturated zone to the 2010 Maule earthquake and 5) responses of the vadose zone to this earthquake. Re 1) In order to quantify the hydrologic impact of plantation forests, it is fundamental to first establish their water balances. I show that tree species is not significant in this regard, i.e. Pinus radiata and Eucalyptus globulus do not trigger any decisive different hydrologic response. Instead, water consumption is more sensitive to soil-water supply for the local hydro-climatic conditions. Re 2) Contradictory opinions exist about whether timber harvest areas (THA) generate or capture overland flow and sediment. Although THAs contribute significantly to hydrology and sediment transport because of their spatial extent, little is known about the hydrological and erosional processes occurring on them. I show that THAs may act as both sources and sinks for overland flow, which in turn intensifies surface erosion. Above a rainfall intensity of ~20 mm/h, which corresponds to <10% of all rainfall, THAs may generate runoff whereas below that threshold they remain sinks. The overall contribution of Hortonian runoff is thus secondary considering the local rainfall regime. The bulk of both runoff and sediment is generated by Dunne, saturation excess, overland flow. I also show that logging may increase infiltrability on THAs which may cause an initial decrease in streamflow followed by an increase after the groundwater storage has been refilled. Re 3) I present changes in frequency-magnitude distributions following seasonal logging by applying Quantile Regression Forests at hitherto unprecedented detail. It is clearly the season that controls the hydro-geomorphic work efficiency of clear cutting. Logging, particularly dry seasonal logging, caused a shift of work efficiency towards less flashy and mere but more frequent moderate rainfall-runoff events. The sediment transport is dominated by Dunne overland flow which is consistent with physics-based modelling using WASA-SED. Re 4) It is well accepted that earthquakes may affect hydrological processes in the saturated zone. Assuming such flow conditions, consolidation of saturated saprolitic material is one possible response. Consolidation raises the hydraulic gradients which may explain the observed increase in discharge following earthquakes. By doing so, squeezed water saturates the soil which in turn increases the water accessible for plant transpiration. Post-seismic enhanced transpiration is reflected in the intensification of diurnal cycling. Re 5) Assuming unsaturated conditions, I present the first evidence that the vadose zone may also respond to seismic waves by releasing pore water which in turn feeds groundwater reservoirs. By doing so, water tables along the valley bottoms are elevated thus providing additional water resources to the riparian vegetation. By inverse modelling, the transient increase in transpiration is found to be 30-60%. Based on the data available, both hypotheses, are not testable. Finally, when comparing the hydrological and erosional effects of the Maule earthquake with the impact of planting exotic plantation forests, the overall observed earthquake effects are comparably small, and limited to short time scales.
Landmanagement und tektonische Prozesse haben einen erheblichen Einfluss auf das Abflussverhalten und den Wasser-, sowie den Sedimenthaushalt von Gebirgsregionen. Sowohl forstwirtschaftliche Bewirtschaftung, als auch starke Erdbeben sind Impulse, die hydrologische und Erosionsprozesse, sowie deren Prozessraten beeinflussen. Obwohl zahlreiche Arbeiten bereits den Einfluss von forstlicher Bewirtschaftung (Abholzungen, Aufforstungen) als auch von Erdbeben auf Wasser und Sedimentflüsse dokumentiert haben, bleiben wichtige Fragen offen. Wie entscheidend ist der Zeitpunkts der Abholzung und des nachfolgenden Wiederaufforstens? Wie wirken seismische Störungen auf unterirdische Wasserflüsse? Wie ändert sich die geomorphologische Arbeit nach Kahlschlägen? Zur Erforschung dieser Fragen bietet sich das südliche Zentralchile aufgrund seiner hohen lokalen seismischen Aktivität und der kontinuierlichen Umwidmung von Flächen in hochproduktive Plantagenwälder hervorragend an. Letztere verursachen sich häufig verändernde Umweltbedingungen durch kurze forstwirtschaftliche Rotationszyklen. Diese Dissertation betrachtet Einzugsgebiete mit vergleichbarer naturräumlicher Ausstattung. Dabei werden experimentelle Datenerhebung, ein Monitoring-Programm und Datenanalysetechniken mit prozessbasierter Modellierung kombiniert. Ziel der vorliegenden Arbeit ist: 1) die Untersuchung des Einflusses von Plantagenwäldern auf den lokalen Wasserhaushalt. Hier zeigt sich, dass die Baumart (Pinus radiata vs. Eucalyptus globulus) keinen entscheidenden Einfluss auf die lokale Wasserbilanz hat. Vielmehr ist der Bodenwasserspeicher unter dem gegebenen lokalen Hydroklima der entscheidende Faktor für den Wasserverbrauch. 2) die Untersuchung des Verhaltens von Kahlschlagflächen im Hinblick auf Quellen oder Senkenwirkung für Oberflächenabfluss und Sedimenttransport. Hier zeigt sich, dass diese Flächen sowohl als Quelle als auch als Senke für Oberflächenabfluss und Sedimenttransport wirken können – abhängig von der Regenintensität. Übersteigt diese ~20 mm/h, was <10 % der lokalen Niederschlagsereignisse entspricht, generieren Kahlschlagflächen Horton-Oberflächenabfluss (Infiltrationsüberschuss) und Sedimenttransport. Unterhalb dieses Schwellenwerts wirken sie als Senke. In Anbetracht der lokalen Niederschlagintensitäten ist der Gesamtbeitrag des Horton-Oberflächenabflusses daher sekundär. Der Großteil des Abflusses entsteht durch Dunne-Oberflächenabfluss (Sättigungsüberschuss). Zudem zeigt die vorliegende Arbeit, dass Abholzen die Infiltrabilität erhöhen kann. Dies führte dazu, dass zunächst der Gebietsabfluss abfällt bevor er erst nach Auffüllen des Grundwasserspeichers signifikant ansteigt. 3) Die Untersuchung des Einflusses von Kahlschlägen auf die hydro-geomorphologische Arbeit und ihre Effizienz. Durch das Anwenden von Quantile Regression Forests (QRF) wird auf kurzer Prozessskala gezeigt, dass Abholzung zu unterschiedlicher Jahreszeit zu signifikanten Veränderungen im Sedimenttransport führt. Vor allem Kahlschläge die während der Trockenzeit durchgeführt werden, verursachten einen Bedeutungsverlust von seltenen, stärkeren Abflussereignissen zu Gunsten der häufigeren, jedoch weniger starken Ereignissen. Hierbei dominierte der Dunne-Oberflächenabfluss. Dies stimmt mit den Ergebnissen eines prozessbasierten hydrologischen Modells (WASA-SED) überein. Es ist somit eindeutig die Jahreszeit, die die Leistung der hydro-geomorphologischer Arbeit nach Kahlschlägen prägte. 4) die Untersuchung von Grundwasserreaktionen auf das M8.8 Maule Erdbeben. Unter Grundwasserbedingungen kann der gesättigte Saprolith mit Verdichtung auf die Erdbebenerschütterungen reagieren. Dieser Prozess erhöht den hydraulischen Gradienten, der eine plausible Erklärung für den beobachteten Anstieg am Gebietsausfluss nach dem Erdbeben liefert. Die Verdichtung mobilisiert Grundwasser, das zudem von der ungesättigten Bodenmatrix aufgenommen werden kann. Hierdurch erhöht sich das Wasservolumen im Wurzelraum und begünstigt die Pflanzaktivität. Eine solche Aktivitätserhöhung spiegelt sich in verstärkten Tagesgängen wider. 5) die Untersuchung von hydrologischen Reaktionen auf das Erdbeben in der ungesättigten Zone. Hier zeigt sich, dass auch Bodenwasser aus der ungesättigten Bodenzone durch Erdbebenerschütterungen freigesetzt werden kann und den darunter liegenden Grundwasserspeicher zufließt. Hierdurch steigt der Grundwasserspiegel in den Talböden und erhöht dort die Pflanzenwasserverfügbarkeit. Durch inverse Modellierung wurde ein erdbebenbedingter Anstieg der Pflanzenaktivität von 30-60% quantifiziert. Beide Hypothesen sind jedoch auf Basis der verfügbaren Daten nicht eindeutig verifizierbar. Vergleicht man den Effekt des Erdbebens auf den Wasserhaushalt mit dem Effekt der exotischen Plantagenwälder zeigt sich, dass die Gesamtwirkung des Erdbebens auf den Wasserhaushalt vergleichsweise klein war und sich zudem auf kurze Zeiträume beschränkte.

Assessment of post-liquefaction residual strength is needed for the development of empirically-based, predictive correlations for earthquake engineering design. Previous practice commonly assigned negligible strengths to liquefied materials for engineering analysis, producing overly-conservative designs. Increasingly available case history data, and improved analytical tools have allowed for more accurate and less overly-conservative estimation of soil residual strength, improving empirical predictive models. This study provides a new case history to the limited suite of (approximately 30) liquefaction failure case histories available for post-liquefaction in-situ strength predictive correlations. This case history documents the Las Palmas gold mine tailings dam failure, resulting from seismic-induced liquefaction during the moment magnitude 8.8 February 27, 2010 Maule, Chile earthquake; the sixth largest since 1900. Forensic analysis provides reasonably well-constrained values of 1) back-calculated representative post-liquefaction residual strength, 2) representative penetration resistance, and 3) representative vertical effective stress along the suspected liquefied failure surface. This study employs the incremental momentum method to incorporate momentum effects of a moving soil mass. The incremental momentum method requires a series of cross sections animating the geometry of failure progression from initiation to termination, converging on the observed final geometry. Using interpreted soil strength characteristics, an iterative procedure approximates the back-calculated value of post-liquefaction residual strength. Findings of this case history plot well with existing empirical deterministic regression charts and are in general agreement with previous, related efforts. Results yield representative, well-constrained values of: 1) post-liquefaction residual strength ≈ 173 psf, 2) penetration resistance of N1,60,CS ≈ 5 and N1,60 ≈ 2.5, and 3) vertical effective stress ≈ 4,300 lb/ft2, or ≈ 2.0 atm.

Improving seismic hazard analysis is an important part of building safer structures and protecting lives. Since large magnitude earthquakes are rarer than other earthquakes, it is harder to model seismic hazards such as lateral spread displacements for these events. Engineers are often required to extrapolate current lateral spreading models when designing utilities, bridges, and piers to withstand the ground displacements caused by earthquakes with magnitudes larger than 8.0. This study uses three case histories from the Maule Chile 2010 earthquake (Mw =8.8) to develop recommendations on which models are most accurate for large earthquake events and how to improve the accuracy of the models. Six empirical models commonly used in engineering practice are compared. The model that best matches the Maule Chile case histories uses local attenuation relationships to make it easier to apply the model to any seismic region. Models that use lab data from cyclic shear tests over predict displacements but using a strain-reduction factor with depth significantly improved the accuracy of the results. Site-to-source distances can vary greatly between geographic seismic and faulting mechanisms. For this reason, models that depend on an internal source-to-site distance show less promise with large subduction zone earthquakes throughout the world. Models with site-to-source distances are most accurate in the western United States and Japan because the case histories for these models came from those countries.

Over the past several decades, empirical formulas have been developed and improved to predict liquefaction and lateral spread based on a database of case histories from observed earthquakes, such as Youd et al. (2002) and Rauch and Martin (2000). The 2010 Maule Chile earthquake is unique first of all because it is recent and was not used to develop recent liquefaction and lateral spread evaluation methods, and therefore can be reasonably used to evaluate the effectiveness of such equations. Additionally, the 8.8 magnitude megathrust event fills a significant gap in the databases used to develop these empirical formulas, which tends to under represent large magnitude earthquakes and events which occur along subduction zones. Use of case histories from this event will therefore effectively test the robustness and accuracy of these methods.As a part of this comparison, data will be collected from two piers in Port Coronel, Chile: Lo Rojas or Fisherman's Pier, and el Carbonero. Lo Rojas is a municipally owned pier which failed in the 2010 earthquake. Dr. Kyle Rollins gathered detailed engineering survey data defining lateral spread displacements along this pier in a reconnaissance visit with other GEER investigators after the earthquake. El Carbonero was under construction during the earthquake, but no known lateral displacements were observed. Collaboration with local universities and personnel contributed a great deal of knowledge about the soil profile. In early April 2014, collection of SPT and CPT data began in strategic locations to fill gaps of understanding about the stratigraphy near the two piers. Additional testing will provide necessary information to carry out predictions of displacements using current empirical models, which can then be compared with observed displacements collected after the earthquake. Collected data will also be complied, and this alone will provide useful information as it represents a unique case history for future evaluation.The goals of this study are therefore: (1) Collect data for two piers (Lo Rojas and el Carbonero) in Port Coronel, Chile to provide a useful case history of lateral displacements observed; (2) Conduct a liquefaction and lateral spread analysis to predict displacement of the two piers in question, considering lateral spread and slope stability; (3) Compare predicted values with observed displacements and draw conclusions on the predictive capabilities of analyzed empirical equations for similar earthquakes (4) Make recommendations to improve when possible.

The 2010, moment magnitude 8.8 earthquake that occurred near Maule, Chile caused major damages to several piers in the Port of Coronel located approximately 160 kilometers (100 miles) to the South of the earthquake epicenter. One of the piers, the North Pier, experienced significant lateral spreading that was caused from liquefaction of the soils at the approach zone of the pier. Damages from lateral spreading and liquefaction effects consisted of sheet pile welding ruptures of the cross-support beams, stiffener buckling, pile displacements, pile rotations, and pier deck displacement. Researchers analyzed the North Pier after the earthquake and documented in detail the damage caused by lateral spread displacements. This study introduces a simplified performance-based procedure called the "Simplified Modeling Procedure" that is used for the analysis of piles supporting a pier that are exposed to lateral spread displacements. The procedure uses the software LPILE, a common program for analyzing a single pile under lateral loading conditions, to evaluate a more complex multi-pile pier design. Instead of analyzing each of the piles in a given pier individually, the procedure utilizes what is known as a "Super Pile" approach to combine several piles into a single representative pile during the analysis. To ensure displacement compatibility between each "Super Pile" in the analysis, the "Super Piles" are assumed to be fully connected at the top of each "Super Pile" to the pier deck. The Simplified Modeling Procedure is developed and tested using the case study history of the North Pier from the Port of Coronel during the 2010 Maule earthquake. The Simplified Modeling Procedure incorporates p-y springs with a lateral push-over analysis. This approach allows the analysis to be performed in a matter of seconds and allows the user to more easily draw the needed correlations between the rows of piles. This procedure helps identify that different rows of piles either contribute to the movement of the pier or contribute to the bracing of the pier. The procedure ultimately predicts the anticipated pier deck deflection by determining when all the pile rows and their respective shear forces are in equilibrium. The Simplified Modeling Procedure predicted that the North Pier experienced deflections between approximately 0.31 meters (1.01 feet) and 0.38 meters (1.26 feet). The predicted deflections and rotations determined using the procedure were determined to be a relatively close representation of the observations made during the post-earthquake reconnaissance observations.

Reconstruction is the ultimate type of intervention a building can experience, usually contested in the context of built heritage. Records and available remains are used as a way to settle debates around it, primarily associated with monuments, leaving aside other types of heritage such as housing in historical areas. When disasters happen regularly — for example earthquakes — reconstruction processes also occur periodically and are unquestioned, due to the necessity to recover the dwelling space for the affected families. I use the case of Chile as a laboratory since earthquakes occur regularly. Even though changes in regulations have led to safer behaviour of buildings in earthquakes, especially in urban areas, the built heritage has been significantly affected, mainly because of the age of the buildings, lack of maintenance, poor regulations, accumulated damage and overall neglect. The pressure for quick reconstruction has led to a superficial understanding of heritage by offering solutions that ‘look like’ the previous houses but without using actual records and without considering other important aspects of their historical value, such as building techniques and human occupation. As a methodology, I surveyed three heritage areas in Chile — San Lorenzo de Tarapacá, Zúñiga and Lolol — throughout different periods using 3D-laser-scanning complemented by photography and interviews. From this, I explore the potential role of accurate records in what is considered heritage and its reconstruction, understanding the capacity of such technologies to be a virtual database for memory, preservation, demolition, intervention or replica. I also propose a series of alternatives based on using 3D-laser-scanning as a continuous practice of recording, as a post-earthquake assessment tool and as a basis for design, which act as a trigger for speculation and questioning over the nature of rebuilding. With this research, I intend to contribute to a much-needed debate in Chile with further implications for other changing historical environments.

On September 16, 2015, a Mw 8.3 earthquake struck offshore of the north-central Chile coast with a fault-rupture length of approximately 150 km. The earthquake triggered a tsunami that impacted 500 km of coastline from Huasco (28.5°S) to San Antonio (33.5°S), registering as much as 4.5 m on the tide gauge at Coquimbo (30.0°S) with run-up heights >10 m at a few exposed locations between Limarí (30.7°S) and Coquimbo. The tsunami provided an invaluable opportunity to examine the nature of tsunami deposit evidence in a semi-arid, siliciclastic environment, where settings suitable for the preservation of tsunami sedimentation are scarce, thereby improving our ability to identify such evidence in the geologic record. Using before-and-after-tsunami satellite imagery and post-tsunami coastal surveys, we targeted one of the few low-energy depositional terrestrial environments in the tsunami-affected area that had a high potential to preserve the 2015 tsunami deposit and older events: the Pachingo marsh in Tongoy Bay (30.3°S). We employed field and laboratory methods to document the 2015 tsunami deposit and discovered sedimentological evidence of previous tsunami inundation of the site. The 2015 tsunami deposit and an older sand bed ~10 cm lower in the stratigraphy exhibit similar sedimentological characteristics. Both sand beds are composed of poorly to moderately sorted, gray-brown, fine- to medium-grained sand and are distinct from underlying and overlying organic-rich silty sediments. The sand beds are thinner (from ~20 cm to <1 cm) and finer (from medium- to fine-grained sand) at more inland locations, and fine upward. However, the older sand bed extends over 150 m farther inland than the 2015 tsunami deposit. To explore the differences in the offshore ruptures that generated the tsunamis that deposited each sand bed, we employed an inverse sediment transport model (TSUFLIND). Our field survey, sedimentological data, and modeling results infer that the older sand bed preserved at the Pachingo marsh field site was produced by a larger tsunami than the 2015 tsunami. Anthropogenic evidence (copper smelter waste) along with Cs137 and Pb210 dating constrains the magnitude and age of the older sand bed to the last 130 years. Based on historical analysis of recent tsunamis that impacted the Pachingo marsh region, we infer a widespread tsunami in 1922 is the best candidate for depositing the older sand bed at our site, providing first geologic evidence of pre-2015 tsunami inundation along the north-central Chile coast.
Master of Science
On September 16, 2015 a segment of the Chilean subduction zone ruptured off the coast of north-central Chile producing a magnitude 8.3 earthquake. The earthquake created a tsunami that impacted 500 km of coastline and created waves measuring 4.5 m on the tide gauge at Coquimbo (30.0°S) with waves reaching inland to heights >10 m at a few exposed locations. The 2015 event in north-central Chile provided a unique opportunity to study tsunami deposits in semi-arid, sand-dominated environment where preservation of tsunami deposits within coastal sediments is rare, helping improve our ability to identify this type of evidence in the sedimentary record. Using before-and-after-tsunami satellite imagery and post-tsunami coastal surveys, we targeted a marsh in the tsunami-affected area that was capable of preserving the 2015 tsunami deposit and older events: the Pachingo marsh in Tongoy Bay (30.3°S). We employed field and laboratory methods to document the 2015 tsunami deposit and discovered evidence of previous tsunami overwash at the site within the sediments of the marsh. Our field work observations and sedimentary data revealed that in addition to the 2015 tsunami deposit, the site contained an older, anomalous sand bed that we infer to be a tsunami based on its similarity to the modern deposit at the site. Our modeling results suggest that the older sand bed was deposited by a tsunami larger than the 2015 tsunami. Based on historical analysis of recent tsunamis that impacted the Pachingo marsh region, we infer a tsunami in 1922 is the best candidate for depositing the older sand bed at our site. This discovery provides the first evidence of tsunami sediments from pre-2015 tsunami inundation along the north-central Chile coast.

A assistência humanitária em casos de desastres vem desempenhando papel significativo nos estudos da logística atualmente. Neste cenário, onde a participação de militares brasileiros prestando este tipo de assistência tem sido cada vez mais marcante, cabe às instituições que compõem as Forças Armadas brasileiras revisar, documentar e analisar continuamente os processos e métodos quando atuando em assistência humanitária. Este trabalho tem como objetivo apresentar os obstáculos que a Marinha do Brasil encontrou e como foi sua atuação no campo logístico quando participou de ações humanitárias nos terremotos ocorridos no Haiti e no Chile, ambos no ano de 2010. A contribuição desta pesquisa é principalmente servir de fonte documental retratando como foi o apoio prestado pelos militares na época que os eventos ocorreram e a sistemática de abastecimento atualmente empregada pela Força, visando melhorar as decisões a serem tomadas na Marinha do Brasil, quando esta se deparar com casos semelhantes aos que aqui foram tratados. A metodologia de pesquisa utilizada foi de abordagem qualitativa, com objetivo exploratório e descritivo, por meio de pesquisa bibliográfica em conceitos presentes no ramo da logística e em doutrinas legais que regem a logística militar. O estudo de caso pautou-se em apresentar dois eventos e analisar a atuação da Marinha em cada um deles. A revisão e análise dos casos aqui tratados resulta no apoio a novos estudos que visem o aperfeiçoamento de processos e o melhor gerenciamento de cadeias logísticas que sejam capazes de aliviar o sofrimento humano por meio de operações humanitárias.
Humanitarian assistance for disaster events has been playing a significant role in logistics studies nowadays. In this scenario, where the participation of Brazilian military personnel proving this type of assistance has been increasingly important, it is duty of the institutions that compose the Brazilian Armed Forces to continuously review, document and analyze the processes and methods when acting in humanitarian assistance. This dissertation aims to present the obstacles that the Brazilian Navy encountered and how it performed in the logistic field when it participated in humanitarian actions after the earthquakes in Haiti and Chile, both in the year of 2010. The contribution of this research is mainly to serve as a documentary source, depicting the support provided by the military at the time the events occurred and the supply system currently employed by the Force, aiming to improve the decisions to be taken in the Brazilian Navy, when it faces similar cases in the future. The research methodology used was a qualitative approach, with an exploratory and descriptive objective, through a bibliographical research on concepts present in the logistics sector and in legal doctrines that govern the military logistics. The case study consisted in presenting two events and analyzing the Brazilian Navy s performance in each of them. The review and analysis of the cases discussed here results in support for further studies that aim the improvement of processes and the better managing of logistics chains that are capable of alleviating human suffering through humanitarian operations.

Natural disasters in Argentina and Chile played a significant role in the state-formation and nation-building process (1822-1939). This dissertation explores state and society responses to earthquakes by studying public and private relief efforts reconstruction plans, crime and disorder, religious interpretations of catastrophes, national and transnational cultures of disaster, science and technology, and popular politics. Although Argentina and Chile share a political border and geological boundary, the two countries provide contrasting examples of state formation. Most disaster relief and reconstruction efforts emanated from the centralized Chilean state in Santiago. In Argentina, provincial officials made the majority of decisions in a catastrophe’s aftermath. Patriotic citizens raised money and collected clothing for survivors that helped to weave divergent regions together into a nation. The shared experience of earthquakes in all regions of Chile created a national disaster culture. Similarly, common disaster experiences, reciprocal relief efforts, and aid commissions linked Chileans with Western Argentine societies and generated a transnational disaster culture. Political leaders viewed reconstruction as opportunities to implement their visions for the nation on the urban landscape. These rebuilding projects threatened existing social hierarchies and often failed to come to fruition. Rebuilding brought new technologies from Europe to the Southern Cone. New building materials and systems, however, had to be adapted to the South American economic and natural environment. In a catastrophe’s aftermath, newspapers projected images of disorder and the authorities feared lawlessness and social unrest. Judicial and criminal records, however, show that crime often decreased after a disaster. Finally, nineteenth-century earthquakes heightened antagonism and conflict between the Catholic Church and the state. Conservative clergy asserted that disasters were divine punishments for the state’s anti-clerical measures and later railed against scientific explanations of earthquakes.

L’objectif principal de cette thèse est d'effectuer des inversions des données sismologiques afin d'obtenir la distribution de glissement de cinq tremblements de terre qui ont eu lieu dans des zones de subduction. Ils sont les séismes de : Tocopilla 2007( Mw 7. 8) ; Michilla 2007 (Mw 6. 7) et Maule 2010 (Mw 8. 8) lesquelles ont frappé le Chili, et ceux de Iwate 2008 (Mw 6. 8) et Tohoku 2011 (Mw9. 0) au Japon. Nous avons calculé des inversions cinématiques pour tous ces événements et avons fait des inversions dynamiques pour Michilla 2007 et Iwate 2008. Ces inversions ont été réalisées proposant une distribution géométrique a priori de forme elliptique pour la zone de rupture avec une distribution gaussienne de glissement. La recherche de la meilleure solution est réalisée en utilisant l'algorithme de voisinage. Accélérogrammes et GPS en continu (cGPS) ont été utilisés dans l’inversion. Pour l'inversion du séisme de Tocopilla 2007 la solution converge vers une distribution de glissement modélisée par deux ellipses. Similaire a celle proposée par Peyrat et la. (2010). Pour le tremblement de terre de Maule 2010, la solution converge vers une distribution de glissement modelisée par deux ellipses, le glissement maximal est situé sur la cote nord de la rupture sismique. De inversion des accélérogrammes, deux aspérités étaient localisées dans le nord de la rupture, ces aspérités contrôlaient le mouvement dans la zone de fréquences intermédiaires (0,02 Hz a 0,1 Hz). Le tremblement de terre de Tohoku 2011 a été caractérisé par la rupture d'une seule ellipse. A partir de ces résultats, nous avons exploré l'espace de solutions avec une méthode de Monte Carlo ou seulement 3 paramètres sont libérés: la vitesse de rupture, la taille maximale de glissement l'ellipse et la taille de l'ellipse (en gardant le ratio d'aspect fixe entre leurs axes). Entre ces trois paramètres, il existe une forte ambiguïté, ce qui confirme que la solution n'est pas unique. Aussi pour ce tremblement de terre est effectuée une inversion préliminaire avec une discrétisation classique en rectangles, et nous avons trouvé des résultats similaires à l’inversion elliptique. Enfin nous avons fait l'inversion de deux tremblements de terre intraplaques de profondeur intermédiaire (Mw 6. 8). Nous avons fait les premières inversions dynamiques avec la libération de tous les paramètres. Par les inversions de Monte Carlo, nous confirmons que les inversions dynamiques ne sont pas uniques, et que la rupture des séismes est contrôlé par les paramètres de la loi de frottement. Ces paramètres peuvent prendre des valeurs différentes, mais ils sont regroupés dans une valeur spécifique de moment sismique et du paramètre kappa (kappa est un paramètre proportionnel au rapport entre ligue l'énergie libérée et l’énergie disponible pour la rupture sismique)
We study the inversion of the slip distribution of five earthquakes: 3 that occurred in Chile (Tocopilla 2007, Mw 7. 8; Michilla 2007, Mw 6. 7; Maule 2010, Mw 8. 8) and two from Japan (Iwate 2008, Mw 6. 8, Tohoku 2011, Mw 9. 0). Kinematic inversions are made for them with the exception of Michilla 2007 and dynamic inversions were made for Michilla 2007 and Iwate 2008. Inversions are made using an elliptical rupture area which is characterized by a Gaussian distribution of slip. The search for the best solution is approached using the neighborhood algorithm. Strong motion and continuous GPS (cGPS) data were used in the inversion. For Tocopilla 2007 we proposed a slip distribution characterized by two ellipses confirming previous work by Peyrat et al. (2010). For the Maule 2010 earthquake two ellipses were proposed, the results showed that the maximum slip is located on the northern part of the rupture. Here also we identified the asperities that controlled the movement in the range of intermediate frequencies (0. 02 Hz to 0. 1 Hz) in the north of the rupture. The Tohoku 2011 earthquake was characterized by the rupture of one ellipse. Then we searched for the best solution using a Monte Carlo method, we fixed some parameters and released 3 of them: rupture velocity, maximum slip and ellipse size (keeping fixed the aspect ratio between their axes), finding that between these three parameters there are strong links, confirming that the solution is non unique. Also for this earthquake is develops a preliminary inversion using a classical discretization with rectangles, finding similar results to the elliptical inversion. Finally we made the inversion of two intraplate intermediate depth earthquakes of magnitudes around Mw 6. 8. For these earthquakes we made the first full dynamic inversions. Here we confirmed, making Monte Carlo inversion, those dynamics inversions are not unique and that are characterized by the parameters of the friction law. These parameters can take different values, but they share common values of seismic moment and kappa values (kappa is a parameter that relates the energy released with the energy available for the earthquake rupture)
Se invierte la distribucion de deslizamiento de cinco terremotos, 3 ocurridos en Chile (Tocopilla 2007, Mw 7. 8; Michilla 2007, Mw 6. 7; Maule 2010; Mw 8. 8) y dos de Japon (Iwate 2008, Mw 6. 8 y Tohoku 2011, Mw 9. 0). Se realizan inversiones cinematicas para ellos con la excepcion de Michilla 2007 e inversiones dinamicas para Michilla 2007 e Iwate 2008. Las inversiones son hechas proponiendo a priori una distribucion geometrica del area de ruptura formada por una o dos elipses y distribucion gaussiana de deslizamiento. La busqueda de la mejor solucion se realiza utilizando el algoritmo de vecindad. Acelerogramas y GPS continuos (cGPS) fueron invertidos. Para Tocopilla 2007 se obtiene una distribucion de slip caracterizado por 2 elipses. Para el terremoto del Maule dos elipses fueron propuestas encontrandose que el maximo deslizamiento se ubica en la zona norte de una ruptura de casi 500 km; para este terremoto ademas se identificaron las asperezas que controlaron el movimiento en el rango de frecuencias intermedias (0. 02 Hz a 0. 1 Hz) en la zona norte de la ruptura. El terremoto de Tohoku 2011 pudo ser caracterizado por la ruptura de una elipses y luego se realizo una busqueda de la mejor solucion utilizando un metodo de Monte Carlo fijando algunos parametros y liberando solo 3 de ellos: velocidad de ruptura, deslizamiento maximo y el tamano de la elipse (manteniendo fija la razon de aspecto entre sus ejes), encontrando que entre estos tres parametros existen fuertes acoplamientos, confirmando que la solucion no es unica. Tambien para este terremoto se realiza desarrolla una preliminar inversion utilizando una discretizacion clasica de rectangulos, encontrandose resultados similares a la inversion por elipse. Finalmente realizamos la inversion de dos terremotos intraplaca de profundidad intermedia de magnitud cercana a Mw 6. 8. Para estos terremotos nosotros realizamos las primeras inversiones dinamicas liberando todos los parametros. Aqui se confirma, realizando inversiones del tipo Monte Carlo, que las inversiones no son unicas y que la ruptura de los terremotos queda controlada por los parametros de la ley de friccion, pudiendo tomar diferentes valores pero agrupandose en valores especificos de momento sismico y kappa (kappa es un parametro que relaciona la energia liberada con la energia disponible para que el terremoto se propague)

L’étude des séismes géants de subduction présente un intérêt de premier ordre, car ils sontsuffisamment puissants pour exciter le manteau et déclencher sa relaxation visco-élastique. Cephénomène est caractérisé par des déformations à grande échelle spatiale (plusieurs milliers dekilomètres) et temporelle (plusieurs décennies). L’étude des déformations post-sismiques en surfacepar géodésie spatiale permet de contraindre les caractéristiques géométriques et rhéologiques del’interface de subduction, ouvrant ainsi la voie à l’étude du cycle sismique dans sa globalité.Le 27 février 2010 se produit le séisme de Mw 8.8, dans la région du Maule, au large du Chili. Lasubduction de la plaque Nazca sous la plaque continentale Sud-Américaine offre, pour la premièrefois, la possibilité de mesurer de manière continue et dense les déformations post-sismiques sur plusde 1500 km. Par ailleurs, plus de 10 ans de campagnes de mesures GPS, ont permis d’imager uncouplage très hétérogène tout au long de l’interface de subduction. L’imbrication alors visible entreles déformations post-sismiques et inter-sismiques, appuyée par l’étude de la sismicité historique,met ainsi en évidence les interactions inter-segments que seuls les modèles visco-élastiques de cyclesismique permettront de mieux comprendre.Cette thèse a été centrée autour de deux axes principaux, qui conduisent vers l’objectif finaldes modèles visco-élastiques de cycle sismique. Le premier et principal objectif est l’étude desdéformations post-sismiques du Maule. J’ai ainsi traité et analysé les cinq ans de données aprèsle séisme afin d’extraire le champ de déformation post-sismique. Ces données ont alors permis decontraindre les modèles visco-élastiques, grâce à la méthode des éléments finis. Un modèle combinéd’afterslip et de relaxation visco-élastique dans l’asthénosphère et dans un chenal à faible viscositétrès profond, permet ainsi d’expliquer le champ de déformation horizontal mais aussi verticalobservé. L’amplitude et la complexité des déformations en champ proche résulte de "l’afterslip",tandis que la relaxation dans le chenal permet de reproduire le très fort soulèvement de la Cordillèredes Andes. Enfin, la relaxation dans l’asthénosphère est responsable de l’extension sur plusieursmilliers de kilomètres des déformations post-sismiques. De plus, la continuité de l’effort de terrainet le traitement des données recueillies a permis de combler l’ultime gap de données. Il a ainsiété possible de déterminer un champ de vitesse inter-sismique continu sur la quasi totalité del’interface. Finalement, même si un modèle de cycle sismique à l’échelle de la subduction Chiliennen’a pas encore pu être réalisé, le modèle de post-sismique apporte déjà de nouveaux indices sur lesinteractions entre les différents segments de l’interface Chilienne, suite au dernier séisme
The study of giant earthquakes on subduction zone represents a main interest. They are indeedsufficiently powerful to excite the mantle and trigger its viscoelastic relaxation, over a very largespatial (thousands of kilometers) and temporal (several decades) scale. Postseismic deformation,monitored by spatial geodesy, are a proxy to the geometrical and rheological characteristics of thesubduction interface, that will allow us to study the whole seismic cycle.On February 27th 2010 in the region of Maule, Chile, occurs the Mw 8.8 megathrust earthquake.Yet, the subduction of the Nazca plate beneath the continental South-American plate offers, forthe first time, the opportunity to measure continuously and densely the postseismic deformationfollowing the earthquake, over more than 1500 km. Otherwise, more than a decade of GPS repeatedmeasurements allowed to image a very heterogeneous coupling all along the Chilean interface. Thevisible imbrication between postseismic deformation and interseismic loading, supported by historicaland instrumental seismicity, highlights interactions between the segments. Viscoelastic modelsof seismic cycle appears to be the only way to understand these interactions.This PhD focused on two main axes, that will lead to the development of viscoelastic modelsof seismic cycle. The first part was dedicated to the study of postseismic deformation followingthe Maule earthquake. Therefore, we processed and analyzed very precisely GPS data in orderto extract the postseismic pattern and modeled it using the finite elements method. A combinedmodel of afterslip and viscoelastic relaxation in the asthenosphere and in a low viscosity channel,extending deep along the slab, can reproduce the complex deformation pattern, horizontaly and inverticaly. The amplitude and complexity of the near-field deformation result from aseismic slip onthe fault plane, while the great uplift of the Cordillera is reproduced by relaxation in the channel.The far field extension, up to 1600 km, entirely results from relaxation in the asthenosphere. Onthe other hand, the continuity of campaign measurements was the occasion to fill the ultimate gapof data, and thus estimate a continuous interseismic velocity field from the North of the Maulerupture zone up to North Chile. Finally, even if the final viscoelastic models of seismic cycle couldnot be processed yet, the present postseismic model already brings new insights on interactionsbetween the different segments of the Chilean interface, following the last Chilean earthquake

付記する学位プログラム名: グローバル生存学大学院連携プログラム
京都大学
0048
新制・課程博士
博士(社会健康医学)
甲第22151号
社医博第99号
新制||社医||10(附属図書館)
京都大学大学院医学研究科社会健康医学系専攻
(主査)教授 古川 壽亮, 教授 森田 智視, 教授 村井 俊哉
学位規則第4条第1項該当
Doctor of Public Health
Kyoto University
DFAM

Cette thèse présente des résultats basés sur les mesures d'ondes réalisées par le satellite DEMETER. Ce satellite français a été exploité entre les années 2004 et 2010 à l'altitude de ~660 km. Nous nous sommes concentrés sur les mesures des ondes électromagnétiques et de la densité du plasma au voisinage des tremblements de terre imminents .Dans la première partie, nous présentons une étude des variations de la densité du plasma dans le voisinage d'un tremblement de terre très puissant au Chili ( Mω 8.8) qui a eu lieu le 27 Février 2010. Les données enregistrées avant le choc principal le long des orbites proches de l'épicentre ont montré des augmentations de densité du plasma. Dans une deuxième étape, une analyse statistique a été effectuée en utilisant 4 ans de données pour suivre les variations saisonnières de densité. Cette étude montre qu'une augmentation forte de la densité du plasma est très rare dans cette région à l'époque du séisme. Dans la deuxième partie, une étude statistique (~6,5 ans) des variations de l'intensité des ondes TBF est montrée. Nous avons analysé toutes les données mesurées disponibles à proximité (en temps et en distance) de grands séismes (M> ou = 5). Les données relatives à plus de 12000 tremblements de terre ont été comparées avec une distribution de référence non perturbée. Nous confirmons les résultats déjà rapportés de la diminution statistiquement significative de l'intensité des ondes à des fréquences de l'ordre de ~1,7 kHz. Cet effet semble être lié à une diminution de la limite inférieure de l'ionosphére qui affecte les ondes TBF qui se propagent dans le guide Terre-ionosphère.

La convergence continue des plaques entre l'Inde et l'Eurasie au cours des ∼40 millions d'années a créé le plateau tibétain, une région avec une altitude moyenne de ~4500 m, une superficie de plus de 600×1000 km2, et des failles actives et une déformation crustale s'étendent sur plus de 2000 km Asie centrale. Environ la moitié des 36 à 40 mm/a de l’Inde vers le nord se répartit dans le plateau tibétain, ce qui entraîne un épaississement, un raccourcissement, des plis et des systèmes de failles complexes. La déformation crustale active provoque divers styles d'accumulation et de libération de déformation sur les failles crustales, exprimées sous la forme de comportements de failles ou de cycles sismiques distincts. L'étude de la déformation des failles crustales et des cycles sismiques sur le plateau tibétain à l'aide de la géodésie spatiale, c'est-à-dire le système de positionnement global (GPS) et l'interférométrie radar à ouverture synthétique (InSAR), a commencé il y a 30 ans. Actuellement, la géodésie à haute résolution spatio-temporelle nous fournit des données abondantes et une résolution suffisante pour étudier la déformation de la surface du sol associée aux processus du cycle sismique.Dans cette dissertation, je me concentre sur la déformation intersismique le long de trois grands systèmes de failles de glissement du plateau tibétain, la faille Altyn Tagh, le système de failles Haiyuan et le système de failles Xianshuihe-Anninghe-Zemuhe-Xiaojiang (XAZX). J'utilise les observations géodésiques GPS (1999–2018) et InSAR (2003–2016), ainsi que les modèles de dislocations 2D et de blocs 3D, pour inverser les taux de glissement et le couplage des failles intersismiques, évaluer le risque sismique et étudier les cycles sismiques le long de ces failles ; étudier en outre la cinématique de la déformation à travers le plateau tibétain. Mes résultats montrent des taux de glissement allant de ~2 à ~12 mm/a, un couplage de failles intersismiques très hétérogène (coexistant complètement verrouillé avec un fluage total), un potentiel sismique distinct et différents cycles de tremblement de terre le long de ces failles. En particulier, j'identifie deux et un nouveaux segments rampants asismiques le long du système de faille Haiyuan et de la faille Xianshuihe respectivement. Mes résultats d'observation et de modélisation géodésiques démontrent la diversité spatio-temporelle et la complexité de la déformation interstismique des failles dans le plateau tibétain, mettent en évidence l'importance de considérer la déformation verticale dans InSAR et permettent une compréhension nouvelle et approfondie des cycles sismiques le long des trois failles ci-dessus systèmes
Ongoing plate convergence between India and Eurasia during the past ∼40 million years has created the Tibetan Plateau, a region with average elevation of ~4500 m, area of over 600×1000 km2, and active faulting and crustal deformation extends more than 2000 km into central Asia. Approximately one-half of India’s 36–40 mm/a northward motion is partitioned in the Tibetan Plateau, resulting in crustal thickening, shortening, folds, and complex fault systems. The active crustal deformation cause diverse styles of strain accumulation and release on crustal faults, expressed as distinct faulting behavior or earthquake cycles. Investigating into crustal fault deformation and earthquake cycles in the Tibetan Plateau using space-based geodesy, i.e., Global Positioning System (GPS) and Synthetic Aperture Radar Interferometry (InSAR), has started 30 years ago. Currently, high spatial-temporal resolution geodesy provides us with abundant data and sufficient resolution to study the ground deformation associated with earthquake cycle processes.In this dissertation, I focus on the interseismic deformation along three boundary large strike-slip fault systems of the Tibetan Plateau, the Altyn Tagh fault, the Haiyuan fault system and the Xianshuihe-Anninghe-Zemuhe-Xiaojiang fault system (XAZX). I use GPS (1999-2018) and InSAR (2003-2016) geodetic observations, along with 2D dislocation and 3D block models, to invert for slip rates and interseismic fault coupling, assess seismic hazard and investigate earthquake cycles along these faults; moreover, study the kinematics of deformation across the Tibetan Plateau. My results show slip rates ranging from ~2 to ~12 mm/a, highly heterogeneous interseismic fault coupling (fully locked coexist with fully creeping), distinct seismic potential and different earthquake cycles along these faults. In particular, I identify two and one new aseismic creeping segments along the Haiyuan fault system and the Xianshuihe fault respectively. My geodetic observation and modeling results demonstrate the spatio-temporal diversity and complexity of interseismic fault deformation in the Tibetan Plateau, highlight the significance of considering vertical deformation in InSAR, and allow a new and in-depth understanding of earthquake cycles along the above three fault systems

碩士
國立臺灣海洋大學
應用地球科學研究所
104
On February 27, 2010, an earthquake with Mw 8.8 occurred in Maule, Chile, where the Nazca plate is subducting eastward beneath the South American plate. This earthquake was called the 2010 Maule (Chile) earthquake or the 2010 MW 8.8 Chile earthquake. It has been the largest earthquake in the Chile region since the 1960 Mw 9.5 Chile earthquake. Hence, the earthquake came to widespread notice by seismologists. Previous studies investigated rupture features of the 2010 MW 8.8 Chile earthquake based on the view in kinematics. In this study, we made an attempt on examining variations in the radiated seismic energy and static stress drop for further understanding the dynamic rupture features. First, the directivity analysis of surface-wave was used to determine the fault parameters based on the single source with uniform rupture process. Results showed that the event had two rupture directions with different rupture lengths and rupture velocities. A rupture toward N19E had a rupture length of ~300 km with a rupture velocity of ~1.81 km/s and the other toward N196E had a rupture length of ~100 km with a rupture velocity of ~1.23 km/s. The source duration for the earthquake was about 200 s. From the Fourier spectral nodes, the rise time was estimated at 30.6 s, ~0.16 times of the source duration, comparable with previous observations for larger earthquakes (0.15-0.20). In terms of the single source, our results exhibited the rupture features of the 2010 Chile earthquake, which is an event with asymmetric bilateral faulting, fast rupture velocity in the northern rupture and slow rupture velocity in the southern one. Such rupture features are in agreement with previous studies, but the rupture velocities are still slower than those. Subsequently, for investigating the complex rupture features, we adopted a forward P-wave modeling method to infer the multiple sources of the 2010 Chile earthquake by using the stations whose azimuth angles are normal to the rupture direction. Results showed that the earthquake consisted of at least 16 sub-events. The total seismic moment (M0) was 1.021022 Nm, corresponding to MW = 8.6. The estimated radiated seismic energy (ES) was 2.171017 Nm and the ES/M0 ratio is 2.1310-5, consistent with the values in the subduction-zone earthquakes (3-510-5), but not meeting those for tsunami earthquakes (0.7-3.010-6). During the faulting, the fourth sub-event with the duration of 25 s was 35 s later after the onset of the earthquake and had the largest M0 = 2.661021 Nm, but there was no the largest ES and ES/M0 which is probably related to the static stress drop. The estimated static stress drop for each sub-event from their source parameters increased with ES/M0, but not with ES. Up to 60-100 s after the onset, the static stress drop reached to the larger values. This implied uneven strength on the fault plane during the earthquake rupture. The average static stress of the 2010 Chile earthquake was estimated to be 62 bars, higher than those of interplate earthquakes (30 bars). As mentioned above, the 2010 Chile earthquake had a slow rupture velocity from the rupture directivity analysis. As a result, an import rupture feature is that there is high static stress drop along with slow rupture velocity for the 2010 Chile earthquake. This was also similar to the 2011 MW 9.0 Tohoku earthquake. Our results revealed a possible anti-correlation between the static stress drop and rupture velocity. Up to now, this is still an open issue.

碩士
國立臺灣海洋大學
應用地球科學研究所
100
In 1960, the biggest earthquake (M=9.5), the human ever recorded event, occurred in south Chile. Subsequently several mega earthquakes (M >8) occurred, along the plate boundary. This imply that an incomplete release of tectonic energy. In February 27 2010, Chile mega earthquake (M=8.8) occurred at the Maule area in middle of Chile. The epicenter location is 105 km, NNE direction (35.9° S, 72.73° W) from Concepción, the second biggest city in Chile. The main shock, in which the focal depth is about 35 km, is a thrust – type subduction earthquake where the Nazca Plate subduct/collied into the South America Plate (the Chile subduction system). The main shock caused more than 500-km long rupture in the accretionary prism that produced a destructive tsunami. It killed many thousands of people and damaged more buildings. Even up to today, the aftershocks and volcanic activities still occur continuously in this region. In order to understand the processes, we have deployed 18 OBSs at 4 months after the main shock. We recorded a total of 23-day data (July 15 – August 8). In this study, we analyzed the P- and S-wave arrivals. The events were relocated by using one-dimensional local velocity model. Before the trench region the result is shown a sequence of normal faulting events. That sequence is possible because the oceanic plate is hardly to subduct beneath the continental plate, as the result of banding mechanism of oceanic plate. On the other hand, after the trench region most of events occur in the paleo-accretionary and fewer in frontal-accretionary prism, we suggest that this boundary is a high angle splay-fault structure and that maybe imply for possibility of generated tsunami. In this study area, the stress has accumulated since 1835. The amount of stress was released by the main shock occurred in 2010. From the slip model by previous studies, we compare our aftershock result to check the region of incomplete released by this mega earthquake event. Based on the historical studies, the period of the mega earthquake occur between ~80 and ~100 years. Taiwan and Chile region share similar tectonic features that is located along the subdcution zone. By numerous researches in Taiwan region, the splay-fault structures also being observed. If these structures were activated, it may possible generated a destructive tsunami.

This thesis discusses the potential for preserving the cultural assets embodied in built heritage, which is damaged in disasters and further threatened during recovery processes. The general underlying assumption is that the use of reclaimed and recycled building materials is a way to retain heritage and cultural values in a sensitive post-disaster reconstruction. It looks at the development of the reclamation practice in Germany, and through analysis of successes and barriers there, it makes parallel comparisons for opportunities and limitations in the Chilean post- February 27th, 2010 earthquake context. This thesis goes on to propose a housing prototype design, which aims to address the undervaluation of traditional building materials and to recommend improvements to urban quality through the design of a house prototype intended to replace those lost in the earthquake. The design site is Chanco, a town that typifies regional heritage architecture of adobe, timber, ceramic tiles and continuous facades in the Maule region of Chile.

碩士
長庚大學
臨床行為科學研究所
94
Research have documented that natural disaster is one of the major traumatic events that might cause posttraumatic stress disorders in survi- vors. The 1999 Taiwan earthquake has great impact to our society and its aftermath is worthy to study. The present study, as part of a longitudinal research, intends to (1) evaluate the reliability and validity of instruments for screening posttraumatic stress reactions, anxiety, and depression; (2) compare the follow-up data of child survivors in an earthquake-affected area;and (3) examine the effectiveness of a school-based intervention program for high-risk child survivors. Two studies were conducted. In study 1, a follow-up screening of posttraumatic stress reactions, anxiety, and depression for 633 5th and 6th graders in a local elementary school of an earthquake-affected area was conducted four years after the earthquake. The screening instruments included the UCLA Posttraumatic Stress Disorder Index (UCLA-PTSD Index), the Revised Children Manifest Anxiety Scale (RCMAS), and the Children Depression Inventory-Chinese version (CDI-C). The results were then compared with the screening data collected two and a half years after the earthquake. In study 2, a school-based intervention pro- gram was conducted for high-risk children and its efficacy was evaluated. Twenty-one high-risk children were divided into two groups: a cognitive behavioral therapy (CBT) group and a placebo control (PC) group. Seven sessions of group therapy were conducted for the CBT group. The PC group attended 7 group meetings of general activities. Both groups were assessed for their posttraumatic stress reactions, anxiety, and depression before and after their group program as well as at 10-week follow-up. The three instruments, i.e. the UCLA-PTSD Index, the RCMAS, and the CDI-C, have satisfactory internal consistency and test-retest reliability. The factor structures of these three instruments are also similar to pre- vious findings. The results showed that 414 (65.4%) participants reported the 921 earthquake as the most disturbing traumatic event they had ex- perienced. 4.6% of them were at high risk for PTSD. Compared to previous screening data of the same group of children, there is a significant decrease in their overall PTSD reactions across time, except hypervigilance. Contrary to the research hypotheses, there is no signi- ficant difference between the CBT and PC group on all the measures at three assessment time. Further analysis reveals that only those children who have reported the 921 earthquake as the most disturbing traumatic event have benefited from the CBT group. Their PTSD and anxiety scores sig- nificantly decreased after the CBT program. Four years after the 921 earthquake, the PTSD reactions of child survivors have reduced significantly to the level of general population. A school-based CBT program, which focused on the 921 earthquake, has showed some benefit to those children who were traumatized by the earthquake, but its effect is minimal to those who have suffered from other traumatic events. Limitations and clinical implications of this study are discussed and directions for future research are suggested.