The North Anatolian Fault (NAF) is one of the world&rsquo / s largest active continental strikeslip faults, and forms the northern margin of the Anatolian plate. Although its geologic and geomorphologic features are well defined, crustal deformation and associated seismicity around central segment of the NAF is relatively less-known. In this study, we analyzed locations and focal mechanisms of 172 events with magnitude &ge / 3, which are recorded by 39 broadband seismic stations deployed by the North Anatolian Passive Seismic Experiment (2005-2008). Distribution of the events shows that the local seismicity in the area is widely distributed, suggesting a widespread continental deformation, particularly in the southern block. For the entire data set, P- and S- arrival times are picked and events are relocated using the HYPOCENTER program. Then, relocated events which have a good azimuthal coverage with a maximum gap of 120&deg / and at least 13 P- wave readings are selected and 1-D inversion algorithm, VELEST, is used to derive the 1-D seismic velocity model of the region. The final model with updated locations is later put together to the FOCMEC program, to obtain focal mechanisms solutions. In this step, an iterative scheme is applied by increasing the number of data errors. To obtain more unique solutions, first motions of P and SH v phases are used along with SH/P amplitude ratios. Resultant 109 well-constrained focal mechanisms later used to perform stress tensor inversion across the region. Our focal mechanisms suggest a dominant strike-slip deformation along two major fault sets in the region. In the east, E-W trending splays (Ezinepazari, Almus, and La&ccedil / in Kizilirmak) show right-lateral strike-slip motion similar to the NAF whereas in the west, N-S trending faults (Dodurga, Eldivan) show left lateral strike-slip motion. Overall, stress orientations are found as: maximum principal stress, &sigma / 1, is found to be subhorizontal striking NW-SE, the intermediate principle stress, &sigma / 2, is vertically orientated and the minimum principal stress, &sigma / 3, is found to be NE &ndash / SW striking, consistent with the strike-slip regime of the region.

The northwest part of the North America-Caribbean plate boundary zone is characterized by active, left-lateral strike-slip faults that are well constrained seismically and are corroborated by on- and offshore geologic mapping. The onshore plate boundary zone comprises the Motogua and Polochic fault systems of southern Guatemala which join and continue offshore as the Swan Islands fault zone along the southern edge of the Cayman trough. At the Mid-Cayman spreading center in the central Caribbean Sea, the fault motion is transferred at a 100 km wide left-step in the fault system to the Oriente fault zone. A third system, the Walton fault zone, continues east from the Mid-Cayman Spreading center to define the Gonave microplate. Seafloor features produced by strike-slip faulting along the Swan Islands and Walton fault zones have been imaged and mapped using the SeaMARC II side-scan sonar and swath bathymetric mapping system, single-channel seismic data, multichannel seismic data and 3.5 kHz depth profiles. Structures mapped along the Swan Islands and Walton fault zones include: 1) twenty-six restraining bends and five releasing bends ranging in size from several kilometers in area to several hundred kilometers in area; 2)en echelon folds which occur only within the restraining bends; 3) straight, continuous fault segments of up to several tens of kilometers in length; 4) restraining and releasing bends forming in "paired" configurations; and 5) a fault-parallel fold belt fold and thrust belt adjacent to a major restraining bend. The features observed along the Swan Islands and Walton fault systems are compared to other features observed along other strike-slip fault systems, from which empirical models have previously been derived. Based on the features observed in these strike-slip systems, a rigid plate scenario is envisioned where the geometry of the fault and the direction of plate motion have controlled the types of deformation that have occurred. In a related study, microtectonic features in an area of Neogene extension within the northwestern Caribbean plate were investigated in order to provide insight on the nature of intraplate deformation related to the motion along the plate boundary. Microtectonic features were measured in the Sula-Yojoa rift of northwestern Honduras with the intention of inverting the data to estimate stress states responsible for the observed strains. Data inversion for the estimation of stress states could not be undertaken with the available measurements, however, the observations made can be used to support several existing models for the intraplate deformation as well as to encourage the elimination of other models. / text

Thesis (M.S.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaves 155-165). Online version available on the World Wide Web.

Thesis (doctoral)--Universität Potsdam, 2004. / "September 2004"--P. [2] of cover. Vita. Includes bibliographical references (p. [115]-132). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Four folded plates in pocket. Includes bibliographical references (leaves 285-303). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph.D.)--Memorial University of Newfoundland, 1996. / Restricted until November 1997. Bibliography: leaves 228-255. Also available online.

Strike-slip faults evolve to accommodate more fault slip, resulting in less off-fault deformation. In analog experiments, the measured fault slip to off-fault deformation ratios are similar to those measured in crustal strike-slip systems, such as the San Andreas fault system. Established planar faults have the largest fault slip to off-fault deformation ratio of ~0.98. In systems without a pre-existing fault surface, crustal thickness and basal detachment conditions affect shear zone width and roughness. However, once the applied plate displacement is 1-2 times the crustal thickness, partitioning of deformation between fault slip and off-fault distributed shear is >0.90, regardless of the basal boundary conditions. In addition, at any moment during the evolution of the analog fault system, the ratio of fault slip to off-fault deformation is larger than the cumulative ratio. We also find that the upward and lateral propagation of faults as an active shear zone developing early in the experiments has greater impact on the system’s strike-slip efficiency than later interaction between non-collinear fault segments. For bends with stepover distance of twice the crustal thickness, the fault slip to off-fault deformation ratio increases up to ~0.80-0.90, after applied plate displacement exceeds twice the crustal thickness. Propagation of new oblique-slip faults around sharp restraining bends reduces the overall off-fault deformation within the fault system. In contrast, fault segments within gentle restraining bends continue to slip and the propagation of new oblique-slip faults have less effect on the system’s efficiency than for sharp restraining bends.

Globally, deformation along obliquely converging plate margins produce a wide variety of complex fault patterns, including crustal pop-ups, fault duplex structures, restraining bends, and flower structures. Depending on the plate velocity, plate obliquity, crustal rheology, length-scale, and climate, the evolution of faulting into translational and vertical strain can range in complexity and fault slip partitioning (i.e. vertical vs. horizontal strain). In this dissertation I studied two restraining bends to understand how these factors influence patterns of deformation along two major plate boundaries: The North American-Caribbean and the North AmericanPacific plate boundaries. First, I estimate the exhumation and cooling history along the Blue Mountains restraining bend in Jamaica using multiple thermochronometers. Three phases of cooling have occurred within Jamaica: 1) initial rock crystallization and rapid emplacement of plutons from 75-68 Ma, 2) slow cooling from 68-20 Ma, and 3) two-stage exhumation from 20 Ma – Present. During the most recent phase of Jamaica’s cooling history, two stages of exhumation have been identified at 0.2 mm/yr (20 – 5 Ma) and ~1 mm/yr (5 Ma – Present). Given the plate velocity to exhumation rate ratio during the most recent phase, we suggest that the climate of Jamaica increases the erosivity of the Blue Mountain suite, whereby the Blue Mountains may be in an erosional stead-state. Second, I studied the long-term evolution of a restraining bend at San Gorgonio Pass in southern California by relating fault kinematics within the uplifted San Bernardino Mountains to the nearby Eastern California shear zone. Using highresolution topography (i.e. UAV and lidar surveys), I studied the plausibility of faulting along two potentially nascent faults within the San Bernardino Mountains, namely the Lone Valley and Lake Peak faults. We found that while both faults display evidence for Quaternary faulting, deciphering true fault slip rates was challenging due to the erosive nature of the mountainous landscape. Coupled with evidence of Quaternary faulting along other faults within the San Bernardino Mountains, we suggest a western migration of the Eastern California shear zone. / PHD

Ce travail de thèse a pour but d'analyser les variations de vitesses sur des grandes failles décrochantes en contexte intracontinental, capables de produire des séismes de très fortes magnitudes (M > 7.5). Afin d'illustrer c es variations d'activités, cette analyse a été effectuée sur deux zones d'études situées en domaine continental et sismiquement actives: la région ouest de la Mongolie (failles de Bogd et Bolnay) et le nord de l'Iran (failles d'Astaneh et de Tabriz). À partir d'une approche morphotectonique et paléosismologique, les cinématiques, les vitesses de failles et les intervalles de récurrence entre les séismes majeurs ont été estimés, permettant d'analyser les caractéristiques du cycle sismique sur chacune des failles. En Mongolie, les failles de Bogd et Bolnay présentent respectivement des vitesses de ~ 1,2 et 2,6 mm/an, qui semblent être constantes sur la période Pleistocène supérieur-Holocène. Ces deux failles présentent également des glissements caractéristiques et des intervalles de temps similaires entre les séismes majeurs. Les analyses paléosismologiques suggèrent qu'un essaim sismique comparable à celui enregistré au XXème siècle a eu lieu il y a environ 3000 ans.En Iran, une vitesse géologique de 2 mm/an a été estimée sur la faille d'Astaneh et les données paléosismologiques suggèrent des intervalles de récurrence qui varient entre 1600 et 2200 ans, associés à des déplacements en surface compris entre 3 et 4,5 m. Nous avons également estimé une vitesse de 7 mm/an sur la faille de Tabriz, en accord avec les données GPS, suggérant que la vitesse sur cette faille est constante depuis 45 ka. / The aim of this thesis is to analyze if variations in slip rates occur along strike-slip faults, in intracontinental domain, these faults producing large earthquakes (M> 7.5). To illustrate these variations, this work has focused in two area located in the most tectonically active continental domains in the world: in the western part of Mongolia (Bogd and Bulnay faults) and in the northern part of Iran (Astaneh and Tabriz faults). Using morphotectonic and paleoseismological analyses, the kinematics, the slip rates and the recurrence times have been estimated and allow us to describe the characteristics of seismic cycle along these faults. In Mongolia, the slip rates are estimated at ~1.2 and ~2.6 mm/yr along the Bogd and the Bulnay faults, respectively, with no variations of geological slip rates over the Pleistocene-Holocene period. These two faults present characteristic slips and similar recurrence times between large earthquakes. The paleoseismological investigations suggest that a cluster occurred 3000 years ago, similar to the seismic cluster recorded in Mongolia during the XX century. In Iran, the slip rate was estimated to 2 mm/yr along the Astaneh fault and the recurrence times are ranging from 1600 to 2200 years, associated with offsets comprised between 3 and 4.5 m. We have also estimated a slip rate of ~7 mm/yr along the Tabriz fault, in agreement with the present day rate estimated by GPS, suggesting no variations in the slip rate over the past 45 ka.

La Mongolie occidentale a connu une sismicité intracontinentale exceptionnelle au cours de la première moitié du XXe siècle, avec 4 évènements sismiques d'une magnitude supérieure à 7.9, localisés sur des grandes structures décrochantes en régime transpressif senestre. Cette sismicité historique a été qualifiée d’essaim sismique, et des études paléosismologiques indiquent que ce phénomène a déjà pu se produire par le passé (3 à 4 ka). Mais si la partie est de la chaine du Gobi-Altaï a rompu lors du séisme du même nom en 1957 (Mw8) le long de la faille de Bogd orientale (WBF), plusieurs traces de failles affectant des formations Holocènes et présentant des longueurs > 100 km ont été documentées dans la partie ouest du massif, sans pour autant faire l’objet d’études quantitatives.Cette thèse apporte un état des lieux de l’activité sismique dans le Gobi-Altaï, au travers d’une cartographie détaillée des escarpements de failles actives au cours du pléistocène supérieur, associée à une analyse de la segmentation au regard de critères géométriques et cinématiques. Parallèlement, des investigations morphotectoniques et paléosismologiques, couplées à des méthodes de datations au 10Be in situ, OSL et 14C, ont permis de quantifier les vitesses de glissement depuis le Pléistocène supérieur, et les âges des paléo-ruptures au cours de l’Holocène sur les deux principaux décrochements analysés : les failles de la Vallée des Lacs (VOLF), et de Bogd occidentale (WBF) ; des données préliminaires permettent également de contraindre l’âge de la dernière rupture et la vitesse de glissement sur les failles de Tsogt (TF) et de Tsagaan Gol (TGF), situées respectivement dans le prolongement occidental de la WBF et de la VOLF. De plus, des mesures systématiques des décalages cosismiques horizontaux enregistrés par la morphologie, notamment le long de la rupture de surface du séisme de 1957, couplés à l’utilisation et le développement d’une approche statistique de détermination des glissements cosismiques moyens au regard de la segmentation, a permis de déterminer la fonction de distribution du glissement le long de l’EBF sur 3 cycles sismiques, suggérant d’une part une distribution du glissement assez homogène le long de la rupture, et d’autre part que le glissement du séisme généré en 1957 est d’une amplitude comparable de celle des précédents séismes, pour au moins 50 % de la rupture principale. Cette approche de détermination statistique des glissements moyens sur plusieurs cycles sismiques est prometteuse mais présente néanmoins certaines incohérences, et des voies de développement et de validations sont proposées.Les paramètres morphotectoniques et les âges des paléoséismes documentés dans cette thèse présentent une grande cohérence avec les données précédemment acquises sur l’EBF, avec des vitesses de faille lentes (0,7 ± 0,2 mm.a-1 sur la WBF et 0,5 ± 0,1 mm.a-1 sur la VOLF), des périodes de retour longues (4,0 ± 1,2 ka pour la WBF), et des décalages cosismiques relativement importants (2 – 4 m). Nos mesures de vitesses de faille indiquent par ailleurs une distribution de la déformation depuis la EBF vers les WBF et VOLF, séparant la déformation en deux faisceaux de failles, l’un se branchant au nord depuis la VOLF sur la TGF. Les déterminations des âges de paléoséismes indiquent une possibilité de cluster entre les différentes failles étudiées, avec trois ruptures potentiellement synchrones au cours de l’Holocène, dont une, rompant l’intégralité des décrochements analysés (WBF, EBF et VOLF), s’avère être temporellement corrélée au précédent cluster potentiellement identifié à 3 – 4 ka. Les paramètres présentés dans cette thèse permettent finalement de calculer des paléomagnitudes associées aux deniers évènements sur les WBF et VOLF, comprises entre Mw7,6 et Mw8 selon les paramètres et les lois considérés. Ces données fondamentales pourront servir de canevas de base pour les actuelles études d’aléas sismique en Mongolie. / Western Mongolia experienced an exceptional intracontinental seismic activity during the first part of the XXth century, with four seismic events with Mw > 7.9, located on large strike-slip faults with a transpressive left-lateral motion. This historical seismicity has been qualified as a cluster, and paleoseismological studies indicate that this phenomenon might have occurred 3 to 4 ka ago. Although the eastern part of the Gobi-Altai mountain range broke during the eponymous earthquake in 1957 (Mw8) along the Eastern Bogd Fault (EBF), several fault traces affecting Holocene formations and presenting continuous fault length > 100 km have been documented on the western part of the range, while not been the purpose of quantitative studies.This thesis first gives an inventory of the seismic activity within the Gobi-Altai, through detailed mapping of the fault scarps which show activity during the late-Pleistocene, also with an analyze of the fault segmentation regarding to geometric and kinematic criteria. Secondly, some morphotectonical and paleoseismological surveys have been carried on, along with dating techniques as 10Be in situ, OSL and radiocarbon, which allow quantifying the faults slip-rates since late-Pleistocene, and paleo-ruptures ages during the Holocene period on the two main strike slip faults analyzed : the Valley of Lakes Fault (VOLF), and the Western Bogd Fault (WBF); preliminary data also allow quantifying the slip rates and the age of the most recent event along the Tsogt Fault (TF) and the Tsagaan Gol fault (TGF), respectively located in the westward continuation of the WBF and the VOLF. Moreover, systematic lateral offset measurements have been carried on along the faults traces, and especially along the 1957 surface rupture, where a statistical approach based on probability density has been applied in order to assess the average lateral offsets successively recorded by the landforms, and reveals that the slip distribution along the EBF on 3 seismic cycles. This suggests first that the slip distributions rather even along the rupture, and secondly that the slip related to the 1957 earthquake is of the same amount than previous major ruptures on that fault, for half of the main 1957 surface rupture. This approach of average coseismic slip assessment on several seismic cycles is promising, but still presents some inconsistencies, and we propose developments and validation perspectives.Morphotectonic parameters and ages of paleo-earthquakes reported in this thesis present a strong consistency with former studies along the EBF, with slow slip-rates (0,7 ± 0,2 mm.yr-1 on the WBF and 0,5 ± 0,1 mm.yr-1 on the VOLF), and significant left lateral coseismic offsets (2 – 4 m). Our measurements of slip rates indicate furthermore a distribution of the on-fault deformation from the EBF to the WBF and the VOLF, splitting the deformation in two branches, the north one reaching the TGF and the southern one visibly branches on the TF. Assessments of the paleoearthquakes ages show three possible clusters between the studied faults during the Holocene time, and one of them may break the three faults (WBF, EBF and VOLF), and seems as well to correspond to the cluster possibly identified 3-4 kyr ago. The fault parameters presented in this thesis allow computing the paleomagnitudes related to last seismic events along the WBF and the VOLF, ranging from Mw7.6 and Mw8, depending of parameters and empirical relations considered. Finally those fundamental data may serve as basic pattern for current seismic hazard assessments in Mongolia.