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1
Watts, Lee Mark. "The Walls Boundary Fault zone and the Møre Trøndelag fault complex : a case study of two reactivated fault zones." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3878/.
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It is commonly observed that ancient faults or shear zones can become reactivated again and again, either within the same or even superimposed tectonic episodes, yet millions of years apart. Rocks of the continental crust show such effects particularly well, owing to their longevity, because through their buoyancy, continental rocks resist recycling back into the Earth's mantle over long time-scales. The Møre Trøndelag Fault Complex (MTFC), Central Norway and the Walls Boundary Fault (WBF), Shetland, were studied to elucidate the kinematic, geometric and textural evolution, in order to assess fault linkages, fault-rock preservation styles and the controlling factors on fault reactivation The WBF is a crustal-scale, reactivated fault that separates distinctively different basement terranes; the Caledonian front to the west from Dal radian type rocks to the east. The WBF initiated as a late-Caledonian sinistral strike-slip fault (c.l00-200km offset) associated with the development of mylonites and cataclasites. Dextral strike-slip reactivation (c.65km) in the Permo-Carboniferous related to inversion of the Orcadian Basin and led to the development of cataclasite and fault gouge assemblages. Later dip-slip and finally sinistral strike-slip (c.l5km. Tertiary?) reactivation were localised within earlier formed fault gouges. The ENE-WSW-trending MTFC in Central Norway is a 10-20 km wide, steeply dipping zone of fault-related deformation. The MTFC has a prolonged and heterogeneous kinematic history. The complex comprises two major fault strands: the Hitra-Snasa Fault (HSF) and the Verran Fault (VF). These two faults seem to have broadly initiated as part of a single system of sinistral shear zones during Early Devonian times (409+12 Ma). Sinistral transtensional reactivation (dated as Permo-Carboniferous; 291 + 14 Ma) of the ENE-WSW-trending HSF and VF led to the development of cataclasites and pseudotachylites together with the formation of N-S-trending faults leading to the present-day brittle fault geometry of the MTFC. Several later phases of reactivation were focused along the VF and N-S linking structures during the Mesozoic probably related to Mid- Late Jurassic/Early Cretaceous rifting and Late Cretaceous / Early Tertiary opening of the North Atlantic. Based on apparent offshore trends, it has been suggested that the MTFC and the WBF may have been linked at some stage during their evolution and subsequent reactivation. This is consistent with the present study, as early Devonian movements along both the WBF and the MTFC are sinistral. Differences in the magnitude, dynamics and senses of displacement in the Permo-Carboniferous, however, seem to militate against linkage of these faults in the late Palaeozoic. There is no compelling evidence for direct Mesozoic or Tertiary linkage, although both structures were reactivated to some extent during these times. It seems that the formation and reactivation of the WBF and MTFC were associated with broadly similar regional tectonic processes and therefore, to some extent, share similar kinematics. Although both the MTFC and the WBF show clear proof of repeated reactivated, superficially similar geometries or alignments should not be used as a basis for correlating structures, in the absence of direct kinematic evidence. Displacements along the MTFC and the WBFZ are repeatedly localised along the earlier formed fault rocks, suggesting that these fault rocks are intrinsically weak compared to the surrounding rocks. A complex interaction exists between the geometrical properties of the fault network and fault-zone weakening mechanisms operative within fault rocks around the level of the frictional-viscous transition. Together these factors control fault reactivation in the long term. In the case of reactivated, sub-vertical, strike-slip fault zones the preservation and exhumation of these fault rocks both depend on the architecture and magnitude of later reactivations.
2
Najdahmadi, Seyedehbita [Verfasser]. "Imaging the North Anatolian Fault Zone with Fault Zone Head Waves, Reflected and Converted Phases / Seyedehbita Najdahmadi." Berlin : Freie Universität Berlin, 2017. http://d-nb.info/1144270219/34.
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Whitmarsh, Richard Sawyer. "Structural framework of the Fries fault zone south of Riner, Virginia." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09122009-040538/.
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Papaleo, Elvira. "The north Anatolian fault, Turkey : insights from seismic tomography." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=239855.
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The North Anatolian Fault Zone (NAFZ) in Turkey is a major continental strike-slip fault, 1200 km long and with a current slip rate of 25 mm/yr. Historical records show that the NAFZ is capable of producing high-magnitude earthquakes, activating different segments of the fault in a westward progression. Currently, the NAFZ poses a major seismic hazard for the city of Istanbul, which is situated close to one of the two strands into which the fault splays in northwestern Turkey. Understanding of fault zone structure and properties at depth is essential to constrain where deformation occurs within the lithosphere and how strain localises with depth. In fact, geodynamic models explaining surface deformation require knowledge of the width and depth extent of the fault zone in both the crust and upper mantle. In this framework, this thesis aims to provide better constraints on fault zone geometry within the lithosphere. To achieve this objective P and S wave teleseismic tomography have been applied to the data recorded by a dense array of broadband seismic stations (DANA, Dense Array for Northern Anatolia); through teleseismic tomography it was possible to image the NAFZ structure in both the crust and uppermost mantle. In addition, joint inversion i of P-wave teleseismic data and local earthquake data collected using the same array provided a greatly improved resolution within the upper 20 km of the crust. Results from this work highlighted the presence of a shear zone associated to the northern branch of the NAFZ in the study area. The fault zone appears to be 15 km wide within the upper crust and narrows to < 10 km within the lower crust and to Moho depth. In the uppermost mantle its width is constrained to be 30 to 50 km.
5
Koc, Ayten. "Remote Sensing Study Of Surgu Fault Zone." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606611/index.pdf.
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The geometry, deformation mechanism and kinematics of the Sü<br>rgü<br>Fault Zone is investigated by using remotely sensed data including Landsat TM and ASTER imagery combined with SRTM, and stereo-aerial photographs. They are used to extract information related to regional lineaments and tectono-morphological characteristics of the SFZ. Various image processing and enhancement techniques including contrast enhancement, PCA, DS and color composites are applied on the imagery and three different approaches including manual, semi automatic and automatic lineament extraction methods are followed. Then the lineaments obtained from ASTER and Landsat imagery using manual and automatic methods are overlaid to produce a final lineaments map.
The results have indicated that, the total number and length of the lineaments obtained from automatic is more than other methods while the percentages of overlapping lineaments for the manual method is more than the automatic method which indicate that the lineaments from automatic method does not discriminate man made features which result more lineaments and less overlapping ratio with respect to final map.
It is revealed from the detail analysis that, the SFZ displays characteristic deformation patterns of strike-slip faults, such as pressure ridges, linear fault controlled valleys, deflected stream courses, rotated blocks and juxtaposition of stratigraphical horizons in macroscopic scale. In addition to these, kinematic analyses carried out using fault slip data indicated that the Sü<br>rgü<br>Fault Zone is dextral strike-slip fault zone with a reverse component of slip and cumulative displacement along the fault is more than 2 km.
6
Butler, Christopher Anthony. "Basement fault reactivation : the kinematic evolution of the Outer Hebrides Fault Zone, Scotland." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/1427/.
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Moir, Heather. "Modelling fault zone evolution : the effect of heterogeneity." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=13241.
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Dodson, Elizabeth Lauren. "STRUCTURAL GEOLOGY OF THE TRANSYLVANIA FAULT ZONE IN BEDFORD COUNTY, PENNSYLVANIA." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_theses/621.
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Transverse zones cross strike of thrust-belt structures as large-scale alignments of cross-strike structures. The Transylvania fault zone is a set of discontinuous right-lateral transverse faults striking at about 270º across Appalachian thrust-belt structures along 40º N latitude in Pennsylvania. Near Everett, Pennsylvania, the Breezewood fault terminates with the Ashcom thrust fault. The Everett Gap fault terminates westward with the Hartley thrust fault. Farther west, the Bedford fault extends westward to terminate against the Wills Mountain thrust fault. The rocks, deformed during the Alleghanian orogeny, are semi-independently deformed on opposite sides of the transverse fault, indicating fault movement during folding and thrusting.
Palinspastic restorations of cross sections on either side of the fault zone are used to compare transverse fault displacement. The difference in shortening corresponds to the amount of displacement on either side of the transverse fault. The palinspastic restoration indicates a difference in the amount of shortening that will balance farther to the west in the Appalachian Plateau province.
9
Hansen, Lars. "Styles of detachment faulting at the Kane Fracture Zone oceanic core complex, 23°N Mid-Atlantic Ridge." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1402172381&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Stewart, Martyn. "Kinematic evolution of the Great Glen Fault Zone, Scotland." Thesis, Oxford Brookes University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364096.
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Sehhati, Reza. "Probabilistic seismic demand analysis for the near-fault zone." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Dissertations/Fall2008/r_sehhati_120108.pdf.
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Thesis (Ph. D.)--Washington State University, December 2008.<br>Title from PDF title page (viewed on Oct. 22, 2009). "Department of Civil & Environmental Engineering." Includes bibliographical references (p. 166-171).
12
Wu, Jiedi. "New Constraints on Fault-Zone Structure from Seismic Guided Waves." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28873.
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The structure of fault zones (FZs) plays an important role in understanding fault mechanics, earthquake rupture and seismic hazards. Fault zone seismic guided waves (GW) carry important information about internal structure of the low-velocity fault damage zone. Numerical modeling of observed FZGWs has been used to construct models of FZ structure. However, the depth extent of the waveguide and the uniqueness of deep structure in the models have been debated. Elastic finite-difference synthetic seismograms were generated for FZ models that include an increase in seismic velocity with depth both inside and outside the FZ. Strong GWs were created from sources both in and out of the waveguide, in contrast with previous homogenous-FZ studies that required an in-fault source to create GW. This is because the frequency-dependent trapping efficiency of the waveguide changes with depth. The near-surface fault structure efficiently guides waves at lower frequencies than the deeper fault. Fault structure at seismogenic depth requires the analysis of data at higher frequencies than the GWs that dominate at the surface. Adapting a two-station technique from surface wave studies, dispersive differential group arrival times between two earthquakes can be used to solve for FZ structures between the earthquakes. This method was tested with synthetic data and shallow events recorded in the SAFOD borehole in the San Andreas Fault. A pair of deep earthquakes recorded in the SAFOD borehole indicate a ~150 m wide San Andreas Fault waveguide with >20% velocity contrast at 10-12 km depth. With additional earthquakes, the full FZ structure at seismogenic depth could be imaged. Subsurface FZ structure can also be derived from a surface source and receiver array analogous to a body-wave refraction survey. Synthetic seismograms for such source-receiver geometry were generated and verified that FZGWs are refracted by the increase in velocity with depth. Synthetic data from a surface array were successfully inverted to derive FZ structure in the subsurface. The new methods presented in this dissertation extend the potential of FZGWs to image deeper FZ structure than has been uniquely constrained in the past.<br>Ph. D.
13
Toy, Virginia Gail, and n/a. "Rheology of the Alpine Fault Mylonite Zone : deformation processes at and below the base of the seismogenic zone in a major plate boundary structure." University of Otago. Department of Geology, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080305.110949.
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The Alpine Fault is the major structure of the Pacific-Australian plate boundary through New Zealand�s South Island. During dextral reverse fault slip, a <5 million year old, ~1 km thick mylonite zone has been exhumed in the hanging-wall, providing unique exposure of material deformed to very high strains at deep crustal levels under boundary conditions constrained by present-day plate motions. The purpose of this study was to investigate the fault zone rheology and mechanisms of strain localisation, to obtain further information about how the structural development of this shear zone relates to the kinematic and thermal boundary constraints, and to investigate the mechanisms by which the viscously deforming mylonite zone is linked to the brittle structure, that fails episodically causing large earthquakes.
This study has focussed on the central section of the fault from Harihari to Fox Glacier. In this area, mylonites derived from a quartzofeldspathic Alpine Schist protolith are most common, but slivers of Western Province-derived footwall material, which can be differentiated using mineralogy and bulk rock geochemistry, were also incorporated into the fault zone. These footwall-derived mylonites are increasingly common towards the north.
At amphibolite-facies conditions mylonitic deformation was localised to the mylonite and ultramylonite subzones of the schist-derived mylonites. Most deformation was accommodated by dislocation creep of quartz, which developed strong Y-maximum crystallographic preferred orientation (CPO) patterns by prism (a) dominant slip. Formation of this highly-oriented fabric would have led to significant geometric softening and enhanced strain localisation. During this high strain deformation, pre-existing Alpine Schist fabrics in polyphase rocks were reconstituted to relatively well-mixed, finer-grained aggregates. As a result of this fabric homogenisation, strong syn-mylonitic object lineations were not formed. Strain models show that weak lineations trending towards ~090� and kinematic directions indicated by asymmetric fabrics and CPO pattern symmetry could have formed during pure shear stretches up-dip of the fault of ~3.5, coupled with simple shear strains [greater than or equal to]30. The preferred estimate of simple:pure shear strain gives a kinematc vorticity number, W[k] [greater than or equal to]̲ 0.9997.
Rapid exhumation due to fault slip resulted in advection of crustal isotherms. New thermobarometric and fluid inclusion analyses from fault zone materials allow the thermal gradient along an uplift path in the fault rocks to be more precisely defined than previously. Fluid inclusion data indicate temperatures of 325+̲15�C were experienced at depths of ~45 km, so that a high thermal gradient of ~75�C km⁻� is indicated in the near-surface. This gradient must fall off to [ less than approximately]l0�C km⁻� below the brittle-viscous transition since feldspar thermobarometry, Ti-inbiotite thermometry and the absence of prism(c)-slip quartz CPO fabrics indicate deformation temperatures did not exceed ~ 650�C at [greater than or equal to] 7.0-8.5�1.5 kbar, ie. 26-33 km depth.
During exhumation, the strongly oriented quartzite fabrics were not favourably oriented for activation of the lower temperature basal(a) slip system, which should have dominated at depths [less than approximately]20 km. Quartz continued to deform by crystal-plastic mechanisms to shallow levels. However, pure dislocation creep of quartz was replaced by a frictional-viscous deformation mechanism of sliding on weak mica basal planes coupled with dislocation creep of quartz. Such frictional-viscous flow is particularly favoured during high-strain rate events as might be expected during rupture of the overlying brittle fault zone. Maximum flow stresses supported by this mechanism are ~65 Mpa, similar to those indicated by recrystallised grain size paleopiezometry of quartz (D>25[mu]m, indicating [Delta][sigma][max] ~55 MPa for most mylonites). It is likely that the preferentially oriented prism (a) slip system was activated during these events, so the Y-maximum CPO fabrics were preserved. Simple numerical models show that activation of this slip system is favoured over the basal (a) system, which has a lower critical resolved shear stress (CRSS) at low temperatures, for aggregates with strong Y-maximum orientations. Absence of pervasive crystal-plastic deformation of micas and feldspars during activation of this mechanism also resulted in preservation of mineral chemistries from the highest grades of mylonitic deformation (ie. amphibolite-facies).
Retrograde, epidote-amphibolite to greenschist-facies mineral assemblages were pervasively developed in ultramylonites and cataclasites immediately adjacent to the fault core and in footwall-derived mylonites, perhaps during episodic transfer of this material into and subsequently out of the cooler footwall block. In the more distal protomylonites, retrograde assemblages were locally developed along shear bands that also accommodated most of the mylonitic deformation in these rocks. Ti-in-biotite thermometry suggests biotite in these shear bands equilibrated down to ~500+̲50�C, suggesting crystal-plastic deformation of this mineral continued to these temperatures. Crossed-girdle quartz CPO fabrics were formed in these protomylonites by basal (a) dominant slip, indicating a strongly oriented fabric had not previously formed at depth due to the relatively small strains, and that dislocation creep of quartz continued at depths [less than or equal to]20 km. Lineation orientations, CPO fabric symmetry and shear-band fabrics in these protomylonites are consistent with a smaller simple:pure shear strain ratio than that observed closer to the fault core (W[k] [greater than approximately] 0.98), but require a similar total pure shear component. Furthermore, they indicate an increase in the simple shear component with time, consistent with incorporation of new hanging-wall material into the fault zone. Pre-existing lineations were only slowly rotated into coincidence with the mylonitic simple shear direction in the shear bands since they lay close to the simple shear plane, and inherited orientations were not destroyed until large finite strains (<100) were achieved.
As the fault rocks were exhumed through the brittle-viscous transition, they experienced localised brittle shear failures. These small-scale seismic events formed friction melts (ie. pseudotachylytes). The volume of pseudotachylyte produced is related to host rock mineralogy (more melt in host rocks containing hydrated minerals), and fabric (more melt in isotropic host rocks). Frictional melting also occurred within cataclastic hosts, indicating the cataclasites around the principal slip surface of the Alpine Fault were produced by multiple episodes of discrete shear rather than distributed cataclastic flow. Pseudotachylytes were also formed in the presence of fluids, suggesting relatively high fault gouge permeabilities were transiently attained, probably during large earthquakes. Frictional melting contributed to formation of phyllosilicate-rich fault gouges, weakening the brittle structure and promoting slip localisation. The location of faulting and pseudotachylyte formation, and the strength of the fault in the brittle regime were strongly influenced by cyclic hydrothermal cementation processes.
A thermomechanical model of the central Alpine Fault zone has been defined using the results of this study. The mylonites represent a localised zone of high simple shear strain, embedded in a crustal block that underwent bulk pure shear. The boundaries of the simple shear zone moved into the surrounding material with time. This means that the exhumed sequence does not represent a simple 'time slice' illustrating progressive fault rock development during increasing simple shear strains. The deformation history of the mylonites at deep crustal P-T conditions had a profound influence on subsequent deformation mechanisms and fabric development during exhumation.
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Kaduri, Maor. "Interplay between creep/aseismic deformation, earthquakes and fluids in fault zones, with a special emphasis on the North Anatolian fault zone, Turkey." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU040/document.
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Le fluage asismique des failles dans la croûte supérieure est un mécanisme de déformation crucial le long des limites des plaques tectoniques. Il contribue au bilan énergétique du cycle sismique, retardant ou déclenchant le développement des grands tremblements de terre. Un enjeu majeur est de comprendre quels sont les paramètres qui contrôlent la partition entre déformations sismiques et asismiques dans les failles actives tels que la lithologie ou les transformations sous contrainte à toutes échelles et comment cette partition évolue dans le temps. Des observations géologiques réalisées dans ce travail le long de la Faille Nord Anatolienne en Turquie, combinées à des analyses de laboratoire et des traitements d’images, permettent de donner un éclairage nouveau sur ces mécanismes de fluage. En plus, les relations entre déformation finie et transfert de matière ont été utilisées en parallèle avec des données géodésiques pour comprendre l’évolution de ces mécanismes de fluage depuis le début du déplacement de cette faille.Une corrélation claire est observée entre fluage superficiel et composition des gouges de la faille : les segments sismiques sont composés de calcaires massifs sans gouge de faille argileuse alors que les segments asismiques qui fluent comprennent des gouges argileuses résultant de la transformation progressive de roches volcaniques. Dans ces zones de fluage une schistosité espacée se développe durant le premier stade de la déformation conduisant à un litage tectonique de type foliation, au début oblique puis subparallèle à la faille, qui accommode une part de la déformation asismique par dissolution cristallisation sous contrainte. En conséquence, les minéraux solubles comme le quartz et les feldspaths sont dissous conduisant à la concentration passive des phyllosilicates dans les gouges de failles qui sont ensuite altérés par des circulations de fluides produisant des minéraux argileux à faible friction. Dans le même temps les zones endommagées autour de la gouge sont fracturées et les fractures scellées par des carbonates. Ces transformations minérales et structurales amollissent les gouges de failles et durcissent les zones endommagées conduisant à une évolution de la déformation sismique – asismique de diffuse à localisée.Des modèles qui intègrent déformation finie et transfert de matière révèlent deux échelles d’espace de la déformation qui correspondent à une alternance de deux types de bandes de cisaillement avec une schistosité soit oblique soit subparallèle à la faille. Diverses valeurs de la déformation finie ont été estimées pour calculer la proportion de déplacement asismique par rapport au déplacement total sismique et asismique de la faille (80 km). Cette proportion qui dépend de la lithologie de la zone de faille varie de 0.002% dans les zones sismiques calcaires et évolue dans le temps dans les zones asismiques des roches volcaniques de 59% pour les stades précoces à 18% pour les stages récents<br>Aseismic fault creep in the upper crust is a key deformation process along tectonic plate boundaries. It contributes to the energy budget during the seismic cycle, delaying or triggering the occurrence of large earthquakes. One of the greatest challenges is to understand which parameters control the partition between seismic and aseismic deformation in active faults, such as lithology or stress-driven transformations at all scales and how this partition evolves with time. Geological observations along the North Anatolian Fault in Turkey combined with laboratory analyses and imaging techniques performed in the present study shed new light on these mechanisms of fault creep. Moreover, the relationship between finite strain and mass change was compared with geodesy data in order to understand the evolution of these creep mechanisms since the beginning of this fault displacement.A clear correlation is shown between shallow creep and near-surface fault gouge composition: seismic segments of the fault are mostly composed of massive limestone without clay gouges, whereas aseismic creeping segments comprising clay gouges result from a progressive change of volcanic rocks. Within these creeping zones, anastomosing cleavage develops during the first stage of deformation, leading to tectonic layering that forms a foliation, oblique at first and then sub-parallel to the fault. This foliation accommodates part of the aseismic creep by pressure solution. Consequently, the soluble minerals such as quartz and feldspars are dissolved, leading to the passive concentration of phyllosilicates in the gouges where alteration transformations by fluid flow produce low friction clay minerals. At the same time damage zones are fractured and fractures are sealed by carbonates. As a result, these mineralogical and structural transformations weaken the gouge and strengthen the damage zone leading to the change from diffuse to localized seismic-aseismic zones.Models integrating finite strain and mass change reveal two spatial scales of strain that correspond to the alternation of two types of shear bands, with cleavages oriented either oblique or sub-parallel to the fault zone. Various total strain values were estimated in order to calculate the aseismic part of the total 80 km displacement along the locked and creeping sections. The aseismic strain fraction of the total tectonic strain in the fault depends on the fault lithology and varies from 0.002% in seismic zones made of limestone and evolves with time in the creeping zones made of volcanic rocks from 59% in the early stages of fault development to 18% in the recent times
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Martos, Justin Riley. "Fault Mapping with the Refraction Microtremor and Seismic Refraction Methods along the Los Osos Fault Zone." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/873.
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The presence of active fault traces in proximity to any new infrastructure project is a major concern for the design process. The relative displacements that can be experienced in surface fault rupture during a seismic event must be either entirely avoided or mitigated in some way. Blind faults present a significant challenge to engineers attempting to identify these hazards. Current standards of practice employed to locate these features are time consuming and costly. This work investigates the geophysical methods of refraction microtremor (ReMi) and seismic refraction with regard to their applicability in this task. By imaging a distinct lateral variation in the shear wave velocity (Vs) profile across a short horizontal distance, these methods may provide a means of constraining traditional investigation techniques to a more focused area. The ReMi method is still very new, but holds key advantages over other geophysical methods in its ease of application and ability to achieve good results in highly urban settings. It is one of the few geophysical techniques that does not suffer in the presence of high amplitude ambient vibrations. The seismic refraction method is here applied in an attempt to corroborate data obtained through the ReMi analysis procedure. Sensitivity, precision parametric studies are carried out in order to learn how to best apply the ReMi method. Both tests are then applied at a previously trenched fault trace to determine whether the data can be matched to the subsurface information. Finally, the methods are deployed at a location with an inferred fault trace where little to nothing is known about the subsurface. The precision study indicates a coefficient of variation for the ReMi method on the order of 7%. At the known fault trace both methods generally agree qualitatively with available subsurface data and each other. Using the ReMi method, a marked shift is observed in the Vs profile laterally across the fault trace. In the case of the inferred fault trace, the same type of lateral variation in the Vs profile is observed using the ReMi method. The seismic refraction at this site does not agree with the ReMi data, but seems reasonable given the visible geomorphology. Receiver arrays placed in close proximity to the inferred fault trace recorded erratic signals during seismic refraction testing, and displayed abnormal response modes after transforming the ReMi data to frequency-slowness space. These anomalies may possibly be attributed to the presence of abnormal subsurface structural geometry indicative of faulting.
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Dehler, Sonya Astrid. "A seismic refraction study of the Queen Charlotte fault zone." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25867.
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The margin between the continental North American and oceanic Pacific plates west of the Queen Charlotte Islands is uniquely marked by an active transform fault zone. The region is the locus of oblique convergence between the two lithospheric plates. West of the fault zone the absent continental shelf is replaced by a 25 km wide scarp-bounded terrace at 2 km depth which separates the oceanic and continental crust.
An onshore-offshore seismic refraction survey was carried out in 1983 across the Queen Charlotte Islands region. Thirty-two explosive charges and several airgun lines were recorded on eleven land-based and six ocean-bottom instruments. A subset of the resulting data set was chosen to study the structure of the Queen Charlotte Fault zone and adjacent terrace.
Two-dimensional ray tracing and synthetic seismogram modelling produced a velocity structural model of the fault region. Underlying the deformed terrace sediments is an upper 3 km thick faulted unit with velocity 3.8 km/s and a high gradient. The lower crustal region is on average 10 km thick and has velocity 5.3 km/s and a slightly lower gradient. Beneath this unit the Moho increases in dip from 5° to 19° eastward. The terrace velocities are anomalously low compared to the adjacent oceanic and continental crustal structures. Velocities of the oceanic crust are consistent with those observed in ophiolite sequences. The velocity structure of the continental crust is not well-defined; however, vertical offset of 1.1 km is seismically observed on the Rennell-Louscoone Fault on Moresby Island.
Two tectonic mechanisms are proposed to explain the anomalous terrace structure. Subduction of the oceanic lithosphere beneath the terrace would accrete sediments to the seaward edge of the terrace and subduct material beneath it. Upthrusting of terrace material along near-vertical fault planes would result from compression at the transform fault above an inactive subduction zone. A combination or alternation of the two mechanisms would explain the observed fault zone structure.<br>Science, Faculty of<br>Earth, Ocean and Atmospheric Sciences, Department of<br>Graduate
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Mair, Karen. "Experimental studies of fault zone development in a porous sandstone." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/12553.
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This study investigates the processes involved in the formation and evolution of faulting in high porosity sandstone using laboratory triaxial compression testing. Faults in highly porous sandstone significantly affect the porosity and permeability of the rock, and typically occur as anastamosing compound bands of damage. Previously only the individual unit of these deformation band structures had been re-produced in the laboratory, possibly due to limitations on sample size. Now by deforming large specimens, I have not only produced zones of deformation bands, but also observed their hierarchical development as a function of strain - for the first time. A series of dry tests were carried out on initially intact 100mm diameter cores of Locharbriggs sandstone, at a constant confining pressure of 34.5MPa, a constant axial strain rate of 5x10E-6/s and increasing amounts of axial strain. Samples were driven over their failure curves and then subjected to differing amounts of post failure sliding. A second series of tests were carried out at increasing confining pressure (in the range of 13.8MPa to 55.2MPa) and constant amounts of axial strain. The response of the rock to the loading conditions was continuously monitored throughout the tests by recording the axial load, the axial strain and volumetric strain. Deformation structures and gouge material produced were studied by hand specimen, thin section and laser particle size analyses. The samples exhibited essentially brittle behaviour with small amounts of strain hardening and softening occurring near peak stress. Dynamic failure was accompanied by a measurable stress drop, which systematically decreased in magnitude as a function of confining pressure. Both compaction and dilatancy are observed in the volumetric strain curves. The amount of dilatancy decreased systematically with increasing confining pressure, until at high confining pressures, compactive behaviour dominated.
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Taylor, Rochelle Louise. "Acoustic velocity structure of the carboneras fault zone, SE Spain." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/acoustic-velocity-structure-of-the-carboneras-fault-zone-se-spain(63a8ae72-04e3-4ab8-bf38-dc215cabbeec).html.
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The Carboneras fault zone (CFZ, Almería Province, SE Spain) is a major NE-SW trending tectonic lineament that marks part of the diffuse plate boundary between Iberia and Africa. Developed within a basement terrain dominated by mica schist, the fault system comprises two main strands within a complex zone up to 1 km wide. Between these two strands is a braided network of left-lateral strike-slip, phyllosilicate-rich fault gouge bands, ranging between 1 and 20 m in thickness, passively exhumed from up to 3 km depth. The excellent exposure in a semi-arid environment, the wide range of rock types and fault structures represented and the practicality of carrying out in-situ geophysical studies makes this fault zone particularly well suited to verifying and interpreting the results of in-situ seismic investigations. Integration of elements of field study, laboratory analysis and modelling has aided interpretation of the internal structure of the fault zone. Ultrasonic measurements were made using standard equipment over confining and pore pressure ranges appropriate to the upper 10 km of the continental crust. Seismic velocities have also been approximated from modal analysis and mineral phase elastic properties and adjusted for the effects of porosity. In-situ seismic investigations recorded P-wave velocities 40-60% lower than those measured in the laboratory under corresponding pressures and at ambient temperatures for hard rock samples. Fault gouge velocities measured in the laboratory, however, are comparable to those measured in the field because, unlike the host rocks, fault gouges are only pervasively micro-fractured and lack the populations of long cracks (larger than the sample size) that cause slowing of the velocities measured in the field. By modelling the effect of fractures on seismic velocity (by superimposing upon the laboratory seismic data the effects of crack damage) the gap between field- and laboratory-scale seismic investigations has been bridged. Densities of macroscopic cracks were assessed by measuring outcrop lengths on planar rock exposures. Assuming crack length follows a power law relation to frequency, this fixes a portion of the power spectrum, which is then extrapolated to cover the likely full range of crack sizes. The equations of Budiansky and O'Connell (1976), linking crack density to elastic moduli, were used to calculate modified acoustic velocities, and the effects of the wide range of crack sizes were incorporated by breaking the distribution down into small sub-populations of limited range of crack density. Finally, the effect of overburden pressure causing progressively smaller cracks to close was incorporated to predict velocity versus depth of burial (i.e. pressure). Determination of rock physical properties from laboratory analysis and sections constructed from geological mapping provides a representation of velocity from selected parts of the Carboneras fault zone. First break tomography images show particularly well the location of steeply-inclined fault cores, and these correlate generally well with geological mapping and laboratory velocity measurements corrected for the effect of cracks. The decoration of the fault zone with intrusive igneous material is well correlated with the results of geological observations. Comparisons made between the field (seismic) inversion model and laboratory forward velocity model in El Saltador valley show the laboratory and field velocity measurements made within the fault zone can be reconciled by accounting for the effects of crack damage in field data.
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Wallis, David. "Micro-geodynamics of the Karakoram Fault Zone, Ladakh, NW Himalaya." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/6805/.
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Microgeodynamics relates grain-scale deformation microstructures to macroscopic tectonic processes. Here the microgeodynamic approach combines optical and electron microscopy, including electron backscattered diffraction (EBSD), with field geology, geothermobarometry and microphysical modelling to study fault rocks deformed within a major continental strike-slip fault to quantify changes in fault zone structure and rheology with crustal depth. The overall thesis rational therefore is to test existing fault models against an exhumed example of a continental strike-slip fault zone, namely the central Karakoram Fault Zone (KFZ), NW India. This approach establishes changes in deformation processes with depth in the upper- to mid-crust and suggests that a range of fault weakening mechanisms have reduced fault rock shear strengths, typified by friction coefficients of 0.3-0.4. Metamorphic petrology and geothermobarometry are used to place the KFZ in the context of regional tectono-metamorphic evolution. It is shown using diagnostic microstructures and pressure-temperature-time paths that the fault initiated after peak metamorphism (677-736°C, 875-1059 MPa) and subsequent migmatisation (688±44°C, 522±91 MPa) and leucogranite emplacement (448±100 MPa). Retrograde phyllonites formed during later strike-slip deformation are investigated in detail using EBSD, geothermometry and microphysical modelling. The phyllonites formed at 351±34°C and had low shear strength (<30 MPa) during frictional-viscous flow. EBSD is also used to derive a novel strain proxy based on quartz crystal preferred orientation intensity. Application of this method distinguishes deformation distributions in transects across the KFZ. Deformation intensity varies from <0.2 in essentially undeformed domains to 1.6 within shear zone strands formed at 500-550°C and c. 15 km depth. Evaluation of the history of the KFZ suggests that whilst it plays a relatively minor role in accommodating India-Asia collision, it can nevertheless be used as an analogue for major continental strike-slip fault zone structure.
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Nishiwaki, Takafumi. "Comparison of Damage Zones of the Nojima and the Asano Faults from the Deep Drilling Project: Differences in Meso-to-microscale Deformation Structures related to Fault Activity." Kyoto University, 2020. http://hdl.handle.net/2433/253096.
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Bullock, Rachael Jane. "Fault zone architecture, microstructures, deformation mechanisms and frictional behaviour of seismogenic, shallow-crustal, lithologically heterogeneous faults." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11293/.
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Earthquakes that rupture the Earth’s surface are typically the most damaging and highlight the need for us to better constrain the style of deformation and frictional behaviour of fault zones in the shallow crust. This thesis presents two studies of natural, seismogenic, shallow crustal fault zones: 1) the Gubbio fault zone, which has been exhumed from 2.5-3 km depth and deforms a mixture of limestone and phyllosilicate-rich marly limestone; and 2) the Masada fault zone, which deforms near-surface, poorly lithified lake sediments. Field studies were complemented by low- and high-velocity rotary shear experiments to constrain the frictional behaviours of the naturally observed fault gouges under representative conditions. In addition, microstructural analyses of both naturally- and experimentally-produced fault rocks were performed in order to constrain the deformation mechanisms operating during fault slip. Our results show that the dominant deformation mechanisms operating within a fault zone, which are highly variable depending on environmental conditions such as depth, fault rock composition, fluid presence and composition, and strain-rate, will control: 1) fault zone architecture and therefore the distribution of seismicity; and 2) slip zone processes, which can subsequently affect the frictional behaviour of a fault, and also determine whether or not signatures of seismic slip are produced during rupture propagation. These are useful tools for geologists when trying to decipher the seismic history of natural faults. Frictional behaviour, in terms of the likelihood of rupture propagation through the shallow crust, is also found to vary significantly as a function of the aforementioned environmental conditions. A fuller knowledge of spatial, and possible temporal, variations in fault zone properties is therefore essential if more accurate earthquake forecasting models and assessments of their associated hazards are to be produced.
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Richey, David J. "Fault Seal Analysis for CO2 Storage: Fault Zone Architecture, Fault Permeability, and Fluid Migration Pathways in Exposed Analogs in Southeastern Utah." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/6060.
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Geologic storage of anthropogenic carbon dioxide (CO2) by injection into underground porous sandstone reservoirs has been proposed as a method for the reduction of anthropogenic greenhouse gas emissions. Upwards migration and leakage of injected fluids along natural fault and fracture networks is a key risk factor for potential injection locations. We examine exposed natural analogs to evaluate the impacts of faulting and fracturing on reservoir and top-seal pairs and to evaluate evidence for paleomigration of fluids along the fault zone.
We examine the Iron Wash fault, a 25-km long normal fault which cuts Jurassic sedimentary rocks and has throws that range from 20-120 m, to examine how a fault may affect seal integrity. Field mapping, kinematic analysis, petrographic analysis, characterization of the fault zone facies and fault architecture, analysis of altered and mineralized rocks in and around the fault zone, and modeling of fault seal capacity was conducted to provide an understanding of the Iron Wash fault zone. Field data and observations were combined with well log and borehole data to produce three types of models for the Iron Wash fault: 1) geometric model of the fault in the subsurface, 2) predictive models of fault zone behavior and fault seal analysis, and 3) predictive geomechanical models of the response of the fault zone to an imposed stress field and increasing the effective stress on the fault.
We conclude that the Iron Wash fault zone has low sealing capacity and will likely not behave as a seal for fluids against the fault zone due primarily to modest throw on the fault and high frequency of fractures associated with the fault zone. Analysis of fluid alteration and mineralization around the fault zone indicates that the fault zone was conduit for paleo-fluids. We conclude that the fault is not likely to develop a sealing membrane and therefore will most likely fail as a seal to fluids moving through the reservoirs modeled here. Modeling results indicate that a reduction in the effective normal stress on fault surfaces may induce failure of faults resulting in earthquakes or increased hydraulic conductivity of fractures.
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Murakami, Masaki. "Zircon fission-track thermochronology of fault zones : short-term heating experiments and thermal history analysis of Nojima fault and Asuke shear zone, Japan." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147835.
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Ryter, Derek. "Late Pleistocene kinematics of the central San Jacinto fault zone, southern California /." view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3072605.
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Thesis (Ph. D.)--University of Oregon, 2002.<br>Typescript. Includes vita and abstract. Includes bibliographical references (leaves 131-137). Also available for download via the World Wide Web; free to University of Oregon users.
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Wu, Chunquan. "Fault zone damage, nonlinear site response, and dynamic triggering associated with seismic waves." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41143.
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My dissertation focuses primarily on the following three aspects associated with passing seismic waves in the field of earthquake seismology: temporal changes of fault zone properties, nonlinear site response, and dynamic triggering.
Quantifying the temporal changes of material properties within and around active fault zones (FZ) is important for better understanding of rock rheology and estimating the strong ground motion that can be generated by large earthquakes. As high-amplitude seismic waves propagate through damaged FZ rocks and/or shallow surface layers, they may produce additional damage leading to nonlinear wave propagation effects and temporal changes of material properties (e.g., seismic velocity, attenuation). Previous studies have found several types of temporal changes in material properties with time scales of tens of seconds to several years. Here I systematically analyze temporal changes of fault zone (FZ) site response along the Karadere-Düzce branch of the North Anatolian fault that ruptured during the 1999 İzmit and Düzce earthquake sequences. The coseismic changes are on the order of 20-40%, and are followed by a logarithmic recovery over an apparent time scale of ~1 day. These results provide a bridge between the large-amplitude near-instantaneous changes and the lower-amplitude longer-duration variations observed in previous studies. The temporal changes measured from this high-resolution spectral ratio analysis also provide a refinement for the beginning of the longer more gradual process typically observed by analyzing repeating earthquakes.
An improved knowledge on nonlinear site response is critical for better understanding strong ground motions and predicting shaking induced damages. I use the same sliding-window spectral ratio technique to analyze temporal changes in site response associated with the strong ground motion of the Mw6.6 2004 Mid-Niigata earthquake sequence recorded by the borehole stations in Japanese Digital Strong-Motion Seismograph Network (KiK-Net). The coseismic peak frequency drop, peak spectral ratio drop, and the postseismic recovery time roughly scale with the input ground motions when the peak ground velocity (PGV) is larger than ~5 cm/s, or the peak ground acceleration (PGA) is larger than ~100 Gal. The results suggest that at a given site the input ground motion plays an important role in controlling both the coseismic change and postseismic recovery in site response.
In a follow-up study, I apply the same sliding-window spectral ratio technique to surface and borehole strong motion records at 6 KiK-Net sites, and stack results associated with different earthquakes that produce similar PGAs. In some cases I observe a weak coseismic drop in the peak frequency when the PGA is as small as ~20-30 Gal, and near instantaneous recovery after the passage of the direct S waves. The percentage of drop in the peak frequency starts to increase with increasing PGA values. A coseismic drop in the peak spectral ratio is also observed at 2 sites. When the PGA is larger than ~60 Gal to more than 100 Gal, considerably stronger coseismic drops of the peak frequencies are observed, followed by a logarithmic recovery with time. The observed weak reductions of peak frequencies with near instantaneous recovery likely reflect nonlinear response with essentially fixed level of damage, while the larger drops followed by logarithmic recovery reflect the generation (and then recovery) of additional rock damage. The results indicate clearly that nonlinear site response may occur during medium-size earthquakes, and that the PGA threshold for in situ nonlinear site response is lower than the previously thought value of ~100-200 Gal.
The recent Mw9.0 off the Pacific coast of Tohoku earthquake and its aftershocks generated widespread strong shakings as large as ~3000 Gal along the east coast of Japan. I systematically analyze temporal changes of material properties and nonlinear site response in the shallow crust associated with the Tohoku main shock, using seismic data recorded by the Japanese Strong Motion Network KIK-Net. I compute the spectral ratios of windowed records from a pair of surface and borehole stations, and then use the sliding-window spectral ratios to track the temporal changes in the site response of various sites at different levels of PGA The preliminary results show clear drop of resonant frequency of up to 70% during the Tohoku main shock at 6 sites with PGA from 600 to 1300 Gal. In the site MYGH04 where two distinct groups of strong ground motions were recorded, the resonant frequency briefly recovers in between, and then followed by an apparent logarithmic recovery. I investigate the percentage drop of peak frequency and peak spectral ratio during the Tohoku main shock at different PGA levels, and find that at most sites they are correlated.
The third part of my thesis mostly focuses on how seismic waves trigger additional earthquakes at long-range distance, also known as dynamic triggering. Previous studies have shown that dynamic triggering in intraplate regions is typically not as common as at plate-boundary regions. Here I perform a comprehensive analysis of dynamic triggering around the Babaoshan and Huangzhuang-Gaoliying faults southwest of Beijing, China. The triggered earthquakes are identified as impulsive seismic arrivals with clear P- and S-waves in 5 Hz high-pass-filtered three-component velocity seismograms during the passage of large amplitude body and surface waves of large teleseismic earthquakes. I find that this region was repeatedly triggered by at least four earthquakes in East Asia, including the 2001 Mw7.8 Kunlun, 2003 Mw8.3 Tokachi-oki, 2004 Mw9.2 Sumatra, and 2008 Mw7.9 Wenchuan earthquakes. In most instances, the microearthquakes coincide with the first few cycles of the Love waves, and more are triggered during the large-amplitude Rayleigh waves. Such an instantaneous triggering by both the Love and Rayleigh waves is similar to recent observations of remotely triggered 'non-volcanic' tremor along major plate-boundary faults, and can be explained by a simple Coulomb failure criterion. Five earthquakes triggered by the Kunlun and Tokachi-oki earthquakes were recorded by multiple stations and could be located. These events occurred at shallow depth (< 5 km) above the background seismicity near the boundary between NW-striking Babaoshan and Huangzhuang-Gaoliying faults and the Fangshan Pluton. These results suggest that triggered earthquakes in this region likely occur near the transition between the velocity strengthening and weakening zones in the top few kms of the crust, and are likely driven by relatively large dynamic stresses on the order of few tens of KPa.
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Heermance, Richard V. "Geometry and Physical Properties of the Chelungpu Fault, Taiwan, and Their Effect on Fault Rupture." DigitalCommons@USU, 2002. https://digitalcommons.usu.edu/etd/6720.
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Rupture of the Chelungpu fault during the September 21, 1999, 7.6 Mwearthquake in Taiwan caused a 90-Jr,m-long surface rupture with variable displacement along strike. Analysis of core from two holes drilled through the fault zone, combined with geologic mapping and detailed investigation from three outcrops, define the fault geometry and physical properties of the Chelungpu fault in its northern and southern regions. In the northern region, the fault dips 45-60° east parallel to bedding and consists of a narrow (1-20 cm) core of dark-gray, sheared clay gouge at the base of a 30-50 m zone of increased fracture density that is confined asymmetrically to the hanging wall. Microstructural analysis of the fault gouge indicates the presence of extremely narrow clay zones (50-300 μm thick) that are interpreted as the fault rupture surfaces. Few shear indicators are observed outside of the fault gouge, which implies that slip was localized in the gouge in the northern region. Slip localization along a bed-parallel surface resulted in less high-frequency ground motion and larger displacements during the earthquake than in the southern region. Observations from the southern region indicate that the fault dips 20-30° at the surface and consists of a wide (20- 70 m-thick) zone of sheared, foliated shale with numerous gouge zones. A footwall-ramp geometry juxtaposes 2000-3000 m of flat-lying Quaternary Toukoshan Formation in the footwall with Pliocene and Miocene, east-dipping siltstone and muds tone in the hanging wall. The wide, diffuse fault zone contributed to the lower displacement and higher frequency ground motion in the southern region during the 1999 earthquake. The structure in the northern region is the result of the fault being a very young (<50 >ka) fault segment in the hanging wall of an older segment of the Chelungpu fault, buried in the Taichung basin. The fault in the southern region is located on an older (~1 Ma) fault trace. The contrasting fault properties in the different regions are responsible for the variability in strong-motion and displacement observed during the 1999 earthquake.
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Li, Qingsong. "Fault evolution and earthquakes a finite element study /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4407.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 28, 2007) Vita. Includes bibliographical references.
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Bradford, Susan Carol. "Kinematics of an accommodation zone in the Rio Grande rift : the Embudo fault zone, northern New Mexico." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1203093704.
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Merson, Matthew. "The Progressive Evolution of the Champlain Thrust Fault Zone: Insights from a Structural Analysis of its Architecture." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/896.
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Near Burlington, Vermont, the Champlain Thrust fault placed massive Cambrian dolostones over calcareous shales of Ordovician age during the Ordovician Taconic Orogeny. Although the Champlain Thrust has been studied previously throughout the Champlain Valley, the architecture and structural evolution of its fault zone have never been systematically defined. To document these fault zone characteristics, a detailed structural analysis of multiple outcrops was completed along a 51 km transect between South Hero and Ferrisburgh, Vermont.
The Champlain Thrust fault zone is predominately within the footwall and preserves at least four distinct events that are heterogeneous is both style and slip direction. The oldest stage of structures—stage 1—are bedding parallel thrust faults that record a slip direction of top-to-the-W and generated localized fault propagation folds of bedding and discontinuous cleavages. This stage defines the protolith zone and has a maximum upper boundary of 205 meters below the Champlain Thrust fault surface. Stage 2 structures define the damage zone and form two sets of subsidiary faults form thrust duplexes that truncate older recumbent folds of bedding planes and early bedding-parallel thrusts. Slickenlines along stage 2 faults record a change in slip direction from top-to-the-W to top-to-the-NW. The damage zone is ~197 meters thick with its upper boundary marking the lower boundary of the fault core. The core, which is ~8 meters thick, is marked by the appearance of mylonite, phyllitic shales, fault gouge, fault breccia, and cataclastic lined faults. In addition, stage 3 sheath folds of bedding and cleavage are preserved as well as tight folds of stage 2 faults. Stage 3 faults include thrusts that record slip as top-to-the-NW and -SW and coeval normal faults that record slip as top-to-the-N and -S. The Champlain Thrust surface is the youngest event as it cuts all previous structures, and records fault reactivation with any top-to-the-W slip direction and a later top-to-the-S slip. Axes of mullions on this surface trend to the SE and do not parallel slickenlines.
The Champlain Thrust fault zone evolved asymmetrically across its principal slip surface through the process of strain localization and fault reactivation. Strain localization is characterized by the changes in relative age, motion direction along faults, and style of structures preserved within the fault zone. Reactivation of the Champlain Thrust surface and the corresponding change in slip direction was due to the influence of pre-existing structures at depth. This study defines the architecture of the Champlain Thrust fault zone and documents the importance of comparing the structural architecture of the fault zone core, damage zone, and protolith to determine the comprehensive fault zone evolution.
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Smith, Paul Malcolm. "Geological setting of mineralization along the Verran Fault zone, central Norway." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338461.
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Sayed, Ali Yawar. "In Situ Compressional Wave Velocity Across An Exposed Brittle Fault Zone." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34336.
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The effects of lithology, fracturing, and gouge zone mineralization on the geophysical properties of fault zones are not very well understood. In situ seismic data collected over the exhumed San Gregorio Fault at Moss Beach, CA were used to relate in situ compressional wave velocity to internal fault zone properties. This active strike-slip fault is exposed in cross section on an uplifting and actively eroding wave-cut platform. It cuts shallow marine sediments that have been buried to depths of a few kilometers. The unweathered exposure containing seawater makes it a unique analog of subsurface faults. Previous structural analysis over this exposure observed damage caused by faulting over a ~100 m wide zone in cross-section. The fault zone is centered at a 10-17 m wide clay-rich fault core flanked by a ~30 m wide brecciated gouge zone. These gouge zones are bordered on either side by 30-40 m wide fractured zones. Resolving to a scale of a few meters, the seismic survey produced a continuous P-wave velocity profile analogous to a horizontal well log across the fault. Lateral variations in the velocity profile correlate exactly to previously mapped fault zone structure. The clay core and adjacent brecciated gouge create a ~50 m wide very low velocity zone, 25-50% slower than the surrounding host rock. Fractured bedrock on either side of the core causes a wider zone of 5-10% slow velocity, for a total fault signature ~100 m wide. Fault parallel fracture anisotropy was observed in the fractured zones, but surprizingly anisotropy was not observed in the strongly foliated gouge zones. The field measurements differ significantly from laboratory measurements at zero pressure and in some cases from expected values for saturated rock of this porosity, perhaps due to biased rock sampling, the long wavelength effects of macrofractures, frequency dispersion, and partial saturation. The velocity profile is similar in width and consistent in velocity contrast to low S-wave velocity zones derived from fault zone guided waves in other strike-slip faults. The traveltime delay across the fault zone is not large enough to cause the 2-3 km wide crustal low velocity zones modeled by refraction studies. Synthetic reflection seismograms in the typical frequency range show that the fault zone acts as a thick bed or as a constructively interfering thin bed. The models suggest that very large reflection coefficients observed across accretionary prism faults can be explained by fracturing, brecciation and clay content without elevated pore pressures. Comparison with a refraction study across the Punchbowl Fault shows a similar structural zonation of these two well-studied examples of brittle fault zones. This suggests that high-resolution seismic velocity models can be used to directly interpret internal deformation structure of brittle faults.<br>Master of Science
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Keighley, Bradbury Kelly. "Rock Properties and Structure Within the San Andreas Fault Observatory at Depth (SAFOD) Borehold, Northwest of Parkfield, California: In Situ Observations of Rock Deformation Processes and Fluid-Rock Interactions of the San Andreas Fault Zone at ~ 3 km Depth." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1410.
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This project examines the composition, structure, and geophysical properties of rocks sampled within the San Andreas Fault Observatory at Depth (SAFOD) borehole drilling experiment near Parkfield, California. Cuttings, sidewall cores, spot-core, and whole-rock core are examined from the meso- to micro-scale to characterize the nearfault environment at shallow crustal levels (0-4 km) along the central segment of the San Andreas fault. The central segment deforms by contiuous aseismic creep and microseismicity. An integrated approach utilizing core-logging, detailed structural core mapping, petrology, microstructural analyses, whole-rock geochemistry, borehole geophysics, and analog field studies is followed.
At SAFOD, fractured granitic rocks and arkosic sediments are identified west of the San Andreas fault zone on the Pacific Plate; whereas sheared fine-grained sediments, ultrafine black fault-related rocks, and serpentinite-bearing fault gouge are present within and northeast of the fault zone on the North American Plate. Here, the fault consists of a broad zone of variably damaged rock containing localized zones of highly concentrated shear that often juxtapose distinct rock-types. Two zones of serpentinite-bearing clay gouge, each meters-thick are found in two locations where active aseismic creep was identified in the borehole. The gouge is composed of Mg-rich clays, serpentinite (lizardite ± chrysotile) with notable increases in magnetite, and Fe-, Ni-, and Cr-oxides/hydroxides and Fe-sulfides relative to the surrounding host rock. Organic carbon is locally high within fractures and bounding slip surfaces. The rocks adjacent to and within the two gouge zones display a range of deformation including intensely fractured regions, blockin- matrix fabrics, and foliated cataclasite structure. The blocks and clasts predominately consist of competent sandstone and siltstone embedded in a clay-rich matrix that displays a penetrative scaly fabric. Mineral alteration, veins, fracture-surface coatings, and slickelined surfaces are present throughout the core, and reflect a long history of syndeformation and fluid-rock reaction that contributes to the low-strength and creep in the meters-thick gouge zones.
Evaluation of borehole geophysical data and elastic modulii for the lithologic and structural units identified in the SAFOD Phase 3 core reveal a correlation between composition and textures and the structural and/or permeability architecture of the SAF at SAFOD. Highly reduced velocity and elastic modulii surround the two serpentinitev bearing gouge zones, the Buzzard Canyon fault to the southwest, and another bounding fault to the northeast. Velocity and elastic moduli values on the Pacific Plate or southeast of the active fault trace intersected by SAFOD are much higher relative to the values measured on the North American Plate, or northeast of the fault trace. Within and adjacent to the two active gouge zones, the rock properties are highly variable over short distances, however, they are significantly lower relative to material outside of the fault zones.
This research contributes critical evidence for rock properties and slip behavior within an active plate boundary fault. Results from this research and the SAFOD experiment help to constrain numerous hypotheses related to fault zone behavior and earthquake generation within central California.
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Traforti, Anna. "Reactivated fault zones: kinematic complexity and fault rock spectral characterization." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421819.
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In the present work three main factors contributing to the overall complexity of reactivated fault zones have been investigated: i) the problematic reconstruction of polyphase brittle tectonic evolution accommodated by fault zones dissecting lithologically heterogeneous rock domains; ii) the estimate of the mechanical anisotropy associated with pre-existing planar discontinuities (i.e., metamorphic foliations and inherited faults) steering their brittle reactivation process; iii) the spectral characterization of fault zone rocks in complex fault architectures aimed at inferring the distribution of fault zone domains by means of remote sensing techniques.
In order to achieve the goal of improving current understanding of these factors defining reactivated fault zone complexity, different methodologies have been applied: i) a paleostress inversion analysis that carefully considers each analyzed fault zones and the different mechanical behavior of the lithological domains they deform; ii) a bootstrapping statistical approach aimed at evaluating the homogeneity between the resulting stress tensors and identifying possible local stress perturbations; iii) a normalised slip tendency analysis that, integrated with paleostress reconstructions and detailed meso- and micro-structural observations, allows constraining the mechanical properties of pre-existing planar discontinuities; iv) a spectral features analysis of fault zone rock reflectance spectra, aimed at highlighting the correlation between variations in fault rock spectral signatures and grain size reduction related to fault comminution processes.
The main results of this work highlighted that: i) polyphase brittle tectonics within lithologically heterogeneous rock domains can be efficiently unrevealed by applying a paleostress inversion combined with bootstrapping statistical analysis of the resulting reduced stress tensors; ii) normalised slip tendency analysis can be considered a reliable method to investigate and constrain the weakness of pre-existing anisotropies at a regional scale (104-103 m); iii) the grain size reduction resulting from fault-related comminution processes on mineralogically homogenous bedrocks (carbonates in this case) influences the spectral signatures of fault rock samples, which absorption feature parameters vary systematically with the grain size in the VNIR and SWIR wavelength ranges; iv) consequently, remote sensing analysis, based on fault rock reflectance spectrum variabilities due to comminution processes, has a good potential in the identification of the spatial distribution and extent of fault core and damage zone domains (i.e., characterized by different grain sizes) on mineralogically homogenous bedrocks (carbonates in this case).<br>Nel presente lavoro sono stati investigati tre fattori che contribuiscono alla definizione della complessità delle zone di faglia riattivate: i) la ricostruzione dell’evoluzione tettonica polifasica accomodata da zone di faglia che interessano litologie eterogenee; ii) la stima del grado di anisotropia meccanica associata alla presenza di discontinuità planari pre-esistenti (i.e., foliazioni metamorfiche e faglie), il quale influenza i meccanismi di riattivazione lungo tali piani; iii) la caratterizzazione spettrale delle rocce di faglia, finalizzata all’ identificazione della distribuzione delle zone di danno e di core tramite tecniche di remote sensing, con particolare riguardo a zone di faglie mature aventi un’architettura complessa. Al fine di dare un nuovo contributo alla comprensione dei fattori che definiscono le complessità insite nelle zone di faglia riattivate, sono state applicate diverse metodologie che comprendono: i) l’inversione del campo di paleostress, applicata considerando il comportamento meccanico dei domini litologici interessati da ogni differente zona di faglia; ii) l’approccio statistico di tipo ‘bootstrapping’ applicato al fine di valutare l’omogeneità tra i tensori di stress ricavati e di identificare possibili perturbazioni locali del campo di paleostress; iii) la ‘normalised slip tendensy analysis’ che, integrata alla ricostruzione del campo di paleostress e ad una caratterizzazione di tipo micro- e meso-strutturale, permette di stimare quantitativamente le proprietà meccaniche di discontinuità planari pre-esistenti; iv) l’analisi delle bande di assorbimento osservate negli spettri di riflettenza di diverse rocce di faglia, al fine di evidenziare il rapporto esistente tra le variazioni osservate nei parametri spettrali e i processi di comminuzione dovuti all’evolversi della zona di faglia stessa.
I principali risultati di questo lavoro evidenziano come: i) tettoniche polifasiche che si sviluppano in domini rocciosi altamente eterogenei possono essere efficacemente ricostruite applicando in maniera integrata l’inversione del campo di paleostress e l’analisi statistica di tipo ‘bootstrapping’; ii) la ‘normalised slip tendency analysis’ permette di investigare la debolezza di anisotropie pre-esistenti a scala regionale (104-103 m); iii) la riduzione granulometrica connessa ai processi di comminuzione dovuti all’evolversi di una zona di faglia in rocce incassanti omogenee dal punto di vista mineralogico (carbonati in questo caso) influenza la firma spettrale delle rocce di faglia, le cui bande di assorbimento hanno caratteristiche che variano sistematicamente con la diminuzione della granulometria; iv) di conseguenza, l’analisi in remoto, basata sugli effetti della comminuzione sulle firme spettrali delle rocce di faglia, dimostra un buon potenziale nell’identificazione della distribuzione spaziale delle zone di danno e di core di una faglia in rocce incassanti omogenee dal punto di vista mineralogico.
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Moser, Amy C. "Spatiotemporal Evolution of Pleistocene and Late Oligocene-Early Miocene Deformation in the Mecca Hills, Southernmost San Andreas Fault Zone." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5992.
Full textAbstract:
Seismogenically active faults (those that produce earthquakes) are very complex systems that constantly change through time. When an earthquake occurs, the rocks surrounding a fault (the “fault rocks”) become altered or damaged. Studying these fault rocks directly can inform what processes operated in the fault and how the fault evolved in space and time. Examining these key aspects of faults helps us understand the earthquake hazards of active fault systems.
The Mecca Hills, southern California, consist of a set of hills adjacent to the southernmost San Andreas Fault. The topography is related to motion on the San Andreas fault, which poses the largest seismic hazard in the lower forty-eight United States. The southernmost San Andreas fault, and the Mecca Hills study location may be reaching the end of its earthquake cycle and is due for a major, potentially catastrophic earthquake. The seismic hazards of the region, coupled with its proximity to major populated areas (Coachella Valley, Los Angeles Basin) make it a critical research area to understand fault zone evolution and the protracted history of fault development.
The goal of this thesis was to directly examine the fault rocks in the Mecca Hills to understand how San Andreas-related faults in this area have evolved and behaved through time. This study integrates a variety of field and laboratory techniques to characterize the structural, geochemical, and thermal properties of the Mecca Hills fault rocks. The results herein document two distinct phases of deformation in the rocks exposed in the Mecca Hills, one around 24 million years ago and the other in the last one million years. This more recent phase of deformation is characterized by fault block exhumation and fluid flow in the fault zones, likely related to changing dynamics of the southernmost San Andreas Fault system. The older event informs how and when these rocks came close to Earth’s surface before the San Andreas Fault initiated.
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Thornock, Steven Jesse. "Southward Continuation of the San Jacinto Fault Zone through and beneath the Extra and Elmore Ranch Left-Lateral Fault Arrays, Southern California." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1978.
Full textAbstract:
The Clark fault is one of the primary dextral faults in the San Jacinto fault zone system, southern California. Previous mapping of the Clark fault at its southern termination in the San Felipe Hills reveals it as a broad right lateral shear zone that ends north of the crossing, northeast-striking, left-lateral Extra fault. We investigate the relationship between the dextral Clark fault and the sinistral Extra fault to determine whether the Clark fault continues to the southeast. We present new structural, geophysical and geomorphic data that show that the Extra fault is a ~7 km wide, coordinated fault array comprised of four to six left-lateral fault zones. Active strands of the Clark fault zone persists through the Extra fault array to the Superstition Hills fault in the subsurface and rotate overlying sinistral faults in a clockwise sense. New detailed structural mapping between the San Felipe and Superstition Hills confirms that there is no continuous trace of the Clark fault zone at the surface but the fault zone has uplifted an elongate region ~950 km. sq. of latest Miocene to Pleistocene basin-fill in the field area and far outside of it. Detailed maps and cross sections of relocated microearthquakes show two earthquake swarms, one in 2007 and another in 2008 that project toward the San Felipe Hills, Tarantula Wash and Powerline strands of the dextral Clark fault zone in the San Felipe Hills, or possibly toward the parts of the Coyote Creek fault zone. We interpret two earthquake swarms as activating the San Jacinto fault zone beneath the Extra fault array. These data coupled with deformation patterns in published InSAR data sets suggest the presence of possible dextral faults at seismogenic depths that are not evident on the surface.
We present field, geophysical and structural data that demonstrate dominantly left-lateral motion across the Extra fault array with complex motion on secondary strands in damage zones. Slickenlines measured within three fault zones in the Extra fault array reveal primarily strike-slip motion on the principal fault strands. Doubly-plunging anticlines between right-stepping en echelon strands of the Extra fault zone are consistent with contraction between steps of left-lateral faults and are inconsistent with steps in dominantly normal faults. Of the 21 published focal mechanisms for earthquakes in and near the field area, all record strike-slip and only two have a significant component of extension. Although the San Sebastian Marsh area is dominated by northeast-striking leftlateral faults at the surface, the Clark fault is evident at depth beneath the field area, in rotated faults, in microseismic alignments, and deformation in the Sebastian uplift. Based on these data the Clark fault zone appears to be continuous at depth to the Superstition Hills fault, as Fialko (2006) hypothesized with more limited data sets.
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Hoffmann-Rothe, Arne. "Combined structural and magnetotelluric investigation across the West Fault Zone in northern Chile." Phd thesis, [S.l.] : [s.n.], 2002. http://pub.ub.uni-potsdam.de/2002/0025/ahoro.pdf.
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Mueller, Sarah Elizabeth. "A seismic reflection study of small offset faults related to the Rough Creek fault zone in western Kentucky /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136087211&sid=20&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Kanaya, Takamasa. "Structure and kinematics of the Suzume fault, Okitsu melange, Shimanto accretionary complex, Japan." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4758.
Full textAbstract:
The Okitsu mélange in the Shimanto accretionary complex, the onshore extension of
the modern Nankai accretionary prism, consists of a kilometer-size duplex of oceanic
basalt and trench-fill sedimentary rocks, and is thought to represent rocks underplated to
the prism along the subduction plate-boundary at seismogenic depth. An internal, horsebounding
thrust of the duplex, referred to as the Suzume fault, juxtaposes basalt in the
hanging wall and sedimentary rocks in the footwall. Structure and fabric of the fault was
characterized at the mesoscale to investigate the processes and structural evolution along
a plate-boundary décollement. The fault zone in the hanging wall consists of decimeterthick
ultracataclasite bounded by a several m thick zone of fractured basalt, and likely
records 2+ km displacement along the thrust. The footwall consists of decimeter-thick
ultracataclasite bounded by a 20-m-thick zone of ductile shear in flattened sedimentary
host rock, and likely records 30+ km of displacement. The asymmetric structure across
the Suzume fault, as well as inferred displacement fields and timing relations, are
consistent with a tectonic model in which the footwall records early ductile, compactive
deformation of poorly consolidated sediments during underthrusting at the prism toe
region, followed by extremely localized cataclasis at the underplating depth. In contrast,
the hanging wall is deformed by intense cataclasis, and only during underplating.
Deformation style and strain state in the footwall of the Suzume fault is qualitatively
similar to the modern Costa Rica underthrust section at the toe region. Similarity in the
structure and fabric of the hanging wall between the Suzume fault and modern
décollement zones sampled through scientific drilling suggests that intense cataclasis
under horizontal contraction likely is a common feature for the hanging wall of the décollement zone throughout the toe to underplating regions. Structures in the Suzume
fault that are not in common with the modern décollements imply progressive
consolidation during underthrusting from the toe to underplating depths may be
responsible for the localization of shear in the footwall. At several kilometers depth,
displacement along the plate boundary is likely accommodated within an extremely
narrow zone as recorded in the ultracataclasite of the Suzume fault.
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Sha'ath, N. A. H. "The structure of the Majma'ah graben complex, central Arabia." Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372040.
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Hoffman, William R. Kirby Eric. "Late Pleistocene slip rates along the Panamint Valley fault zone, eastern California." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4709/index.html.
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Walker, Jessica Gillian. "A study of the deformation environment of the Outer Hebrides Fault Zone." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46600.
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Strane, Michael D. Oskin Michael. "Slip rate and structure of the nascent Lenwood fault zone, Eastern California." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1336.
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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2007.<br>Title from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Master of Sciences in the Department of Geological Sciences." Discipline: Geology; Department/School: Geological Sciences.
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Clarke, Stuart. "Faulting, fault zone processes and hydrocarbon flow through three-dimensional basin models." Thesis, Keele University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394652.
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Taylor, David George. "Multi-scale imaging of the North Anatolian Fault Zone using seismic interferometry." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/21717/.
Full textAbstract:
Seismic imaging allows us to examine the subsurface structure of fault zones. Accurate knowledge of the structure of fault zones is critical for our understanding of earthquake hazard, and the processes of strain accumulation within the crust and upper mantle. The North Anatolian Fault Zone is a ∼ 1200 km long continental strike-slip fault zone located in northern Turkey. In the 20th century, the North Anatolian Fault has accommodated a westward propagating sequence of twelve Mw > 6.5 earthquakes. The most recent of these earthquakes occurred at Izmit and Duzce in 1999, 86 km south-east of Istanbul. In this thesis I use techniques from seismic interferometry to create seismic images of the crustal and upper mantle structure along the Izmit-Adapazari section of the North Anatolian Fault, in the vicinity of the 1999 Izmit rupture. I develop methods for observing P-wave reverberations from the free surface that are contained within the ambient seismic noise field and the P-wave coda of teleseismic earthquakes. By autocorrelating the seismic records from a dense seismic array in north-western Turkey, I use these reverberations to create high resolution seismic reflection images of the crust and upper mantle beneath the North Anatolian Fault Zone. In addition, I calculate inter-station cross-correlations to observe Rayleigh and Love waves propagating between stations in the Izmit-Adapazari region. I then use Rayleigh and Love wave phase velocity measurements to perform surface wave tomography and construct an S-wave velocity model of the top 10 km of the crust in the Izmit-Adapazari region. In the reflection images, I observe a clear arrival associated with a Moho reflected P-wave (PPmP). A ~ 3 s variation in travel time of the PPmP arrival suggests that the Moho is vertically offset beneath the northern branch of the North Anatolian Fault Zone. The vertical offset in the Moho occurs over a region less than 7 km wide approximately 16 km north of the surface trace of the North Anatolian Fault. The location of the vertical offsets indicates that the North Anatolian Fault is a localised structure that dips at an angle between 60◦ and 70◦ through the entire crust and enters the upper mantle as a narrow shear zone. I also note a reduction in the amplitude of the PPmP phase beneath both the northern and southern branches of the North Anatolian Fault Zone. This amplitude reduction could result from the presence of fluids and serpentinite minerals in the upper mantle which reduce Moho reflectivity beneath the North Anatolian Fault. The surface wave tomography shows that the North Anatolian Fault Zone is a vertical zone of low S-wave velocity (2.8 – 3.0 km s−1) in the top 10 km of the crust. I also detect further low velocity anomalies (1.2 – 1.6 km s−1) associated with ~ 3 km deep pull-apart sedimentary basins along both branches of the North Anatolian Fault Zone. Both branches of the North Anatolian Fault appear to skirt the edges of the Armutlu Block, a tectonic unit of crystalline rocks that exhibits high S-wave velocity (3.2 – 3.6 km s−1). It is likely that the Armutlu Block has a strong rheology, and localises strain along the faults at its northern and southern edges. I also measure the azimuthal anisotropy of the phase velocity observations, which displays an average magnitude of ~ 2.5% with a fast direction of 70◦ from north. The 70◦ fast direction aligns parallel with the direction of maximum extension in the Izmit-Adapazari region, and indicates that deformation-aligned mineral fabrics may dominate the anisotropy signal in the top 10 km of the crust.
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Natawidjaja, Danny Hilman Sieh Kerry E. "Neotectonics of the Sumatran Fault and paleogeodesy of the Sumatran subduction zone /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05222003-155554.
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King, Christina. "GPS CONSTRAINTS ON GARLOCK AND EASTERN CALIFORNIA SHEAR ZONE FAULT SLIP RATES." Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192501.
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Koger, Jace. "Spatio-temporal History of Fluid-rock Interaction in the Hurricane Fault Zone." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5911.
Full textAbstract:
The Hurricane Fault is a 250-km long, west dipping, Basin and Range-bounding normal fault in SW Utah and NW Arizona that initiated in the mid-Miocene to Pliocene. It has been primarily active in the Quaternary, with slip rates of 0.2 – 0.6 mm/yr. There are multiple hot springs along its 250-km length and multiple late Tertiary-Quaternary basaltic centers broadly parallel the fault. Possible sources of hot spring fluids include deeply-circulated meteoric water that experienced water-rock exchange at high temperatures (>100 °C) and deep-seated crustal fluids. Aside from the source of modern hot spring fluids and heat, questions about the spatio-temporal history of fluid flow along the Hurricane Fault remain unaddressed. Abundant damage zone veins, cements, and host rock alteration are present, indicative of past fluid flow. Carbonate veining and cementation is a key feature of the Hurricane Fault zone, and is the primary feature exploited to characterize the thermochemical history of fault-related paleofluids. A combination of macroscopic and microscopic carbonate observations, chemical composition, and precipitation temperature of calcite veins was used to determine past water-rock diagenetic interaction and vein evolution in the Hurricane Fault zone. Calcite iv in concretions and veins from the damage zone of the fault shows a wide range of carbon and oxygen stable isotope ratios, with δ13CPDB from -4.5 to 3.8 ‰ and δ18OPDB from -17.7 to -1.1‰. Fluid inclusion microthermometry homogenization temperatures range from 45 to 160 °C, with fluid salinities of 0 to 15 wt% NaCl calculated from melting temperatures. Combining the two datasets, two main fluids that interacted with the fault zone are inferred: (1) basin brines with a δ 18OSMOW of 9.2 ‰ and (2) altered meteoric fluids with a δ 18OSMOW of -11.9 to -8.3 ‰. Calculated dissolved CO2 δ 13CPDB (-8.5 to -1.3 ‰) indicates mixed marine carbonate and organic or magmatic sources. Fault zone diagenesis was caused by meteoric water infiltration and interaction with carbonate-rich rocks, mixed with upwelling basin brines. Fluid-rock interaction is concentrated in the damage zone, where fracture-related permeability was utilized for fluid flow. A distinct mineralization event punctuated this history, associated with basin brines that were chemically influenced by nearby basaltic magmatism. This implies a hydrologic connection between the fault and regional magmatism.
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Hamaker, Sandra Myrtle Conrad. "Relationship Between Fault Zone Architecture and Groundwater Compartmentalization in the East Tintic Mining District, Utah." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1089.pdf.
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Pachell, Matthew A. "Structural Analysis and a Kink Band Model for the Formation of the Gemini Fault Zone, an Exhumed Left-Lateral Strike Slip Fault Zone in the Central Sierra Nevada, California." DigitalCommons@USU, 2001. https://digitalcommons.usu.edu/etd/5244.
Full textAbstract:
The structure and regional tectonic setting of an exhumed, 9.3-km long, left-lateral strike-slip fault zone eludicates processes of growth, linkage, and termination for strike-slip fault zones in granitic rocks. The Gemini fault zone is composed of three steeply dipping, southwest-striking, noncoplanar segments that nucleated and grew along preexisting joints. The fault zone has a maximum slip of 131 m and is an example of a segmented, hard-linked fault zone in which geometrical complexities of the faults and compositional variations of protolith and host rock resulted in nonuniform slip orientations, complex interactions at fault segments, and an asymmetric slip-distance profile. Regional structural analysis shows that joints and left-lateral fault zones have accommodated slip within a 4.8-km wide, right-lateral monoclinical kink band with vertical fold axes and northwest-striking axial surfaces. Geometric modeling of the kink band indicates that as little as 1.1 km of right-lateral displacement across the kink band may have produced the observed slip on kilometer-scale faults within the kink band.
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Zhao, Peng. "Seismic velocity contrasts and temporal changes of strike-slip faults in central California." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37242.
Full textAbstract:
The spatial patterns of bimaterial interfaces along the Parkfield section of the San Andreas Fault (SAF) and central section of the Calaveras Fault are systematically investigated with large data sets of near-fault waveforms. Different from the usage of direct P and S waves in traditional tomographic studies, a particular seismic phase named fault zone head wave (FZHW) is used to image the bimaterial fault interfaces. The results show clear variations of seismic velocities contrast both along-strike and along-depth directions in both regions, which is in general consistent with local geological setting at surface and existing 3D tomography results. In the Parkfield section of SAF, the result of velocity contrast is used to test the relationship between preferred rupture directions of M6 Parkfield earthquakes and bimaterial interface. Strong velocity contrast (~5-10%) near Middle Mountain (MM) could control the rupture directions of nearby earthquakes to SE, such as the case for 1966 M6 Parkfield earthquake. In comparison, weak velocity contrast (~0-2%) near the epicenter of the 2004 Parkfield M6 earthquake (i.e., Gold Hill) probably has no influence on controlling its rupture direction, which is consistent with the bilateral rupture of the 2004 Parkfield earthquake. In the central Calaveras Fault, a detailed analysis of the moveout between FZHWs and direct P waves revealed the existence of a complicated fault structure with velocity contrast increasing from NW to SE of station CCO. The high velocity contrast SE of station CCO could be caused by a low-velocity zone SE of station CCO.
The spatio-temporal variations of seismic velocity around the central Calaveras Fault and its nearby region are investigated based on the waveform analysis of 333 repeating clusters following the 1984 ML6.2 Morgan Hill earthquake. Clear reduction of seismic velocity is shown for all repeating clusters immediately after the mainshock, followed by a logarithmic recovery. The coseismic change mostly occurs at shallow layers (top few hundred meters) for the region away from the rupture area of the mainshock, but extends much deeper around the rupture zone of the Morgan Hill earthquake. The estimated depth of the damage zone is up to 6 km in the fault based on the repeating clusters directly beneath station CCO.
Finally, temporal changes around the Parkfield section of SAF are studied using recently developed ambient noise cross-correlation technique. The extracted daily empirical Green functions (EGFs) from 0.4-1.3 Hz noise records are used to estimate subtle temporal changes associated with large earthquakes from local to teleseismic distances. The results show clear coseismic reduction of seismic velocities after the 2004 M6 Parkfield earthquake, similar to the previous observation based on repeating earthquakes. However, no systematic changes have been detected for other four regional/teleseismic events that have triggered clear tremor activity in the same region. These results suggest that temporal changes associated with distance sources are very subtle or localized so that they could not be detected within the resolution of the current technique (~0.2%).