This study investigates evidence for linkages and fault interactions centred on the Cust Anticline in Northwest Canterbury between Starvation Hill to the southwest and the Ashley and Loburn faults to the northeast. An integrated programme of geologic, geomorphic, paleo-seismic and geophysical analyses was undertaken owing to a lack of surface exposures and difficulty in distinguishing active tectonic features from fluvial and/or aeolian features across the low-relief Canterbury Plains. LiDAR analysis identified surface expression of several previously unrecognised active fault traces across the low-relief aggradation surfaces of the Canterbury Plains. Their presence is consistent with predictions of a fault relay exploiting the structural mesh across the region. This is characterised by interactions of northeast-striking contractional faults and a series of re-activating inherited Late Cretaceous normal faults, the latter now functioning as E–W-striking dextral transpressive faults. LiDAR also allowed for detailed analysis of the surface expression of individual faults and folds across the Cust Anticline contractional restraining bend, which is evolving as a pop-up structure within the newly established dextral shear system that is exploiting the inherited, now re-activated, basement fault zone. Paleo-seismic trenches were located on the crest of the western arm of the Cust Anticline and across a previously unrecognised E–W-striking fault trace, immediately southwest of the steeply plunging Cust Anticline termination. These studies confirmed the location and structural style of north-northeast-striking faults and an E–W-striking fault associated with the development of this structural culmination. A review of available industry seismic reflection lines emphasised the presence of a series of common structural styles having the same underlying structural drivers but with varying degrees of development and expression, both in the seismic profiles and in surface elevations across the study area. Based on LiDAR surface mapping and preliminary re-analysis of industry seismic reflection data, four fault zones are identified across the restraining bend structural culminations, which together form the proposed Oxford–Cust–Ashley Fault System. The 2010–2012 Canterbury Earthquake Sequence showed many similarities to the structural pattern established across the Oxford–Cust–Ashley Fault System, emphasising the importance of identification and characterization of presently hidden fault sources, and the understanding of fault network linkages, in order to improve constraints on earthquake source potential. Improved understanding of potentially-interactive fault sources in Northwest Canterbury, with the potential for combined initial fault rupture and spatial and temporal rupture propagation across this fault system, can be used in probabilistic seismic hazard analysis for the region, which is essential for the suitability and sustainability of future social and economic development.

Geomorphological and paleoseismic studies provide insight into the fault geometry and kinematics of a series of dextral northeast striking faults, including the Porters Pass, Hawdon, Bullock Hill, and Esk faults, in the South Island of New Zealand. These faults show post-glacial offsets that are significantly larger than predicted from co-seismic displacement - surface rupture length regressions derived from empirical relationships. Geomorphological mapping reveals slip rates as high as 9 mm/year for the Hawdon fault and Bullock Hill fault over an expected fault length of c. 140 km. Surface expressions of some parts of the studied faults are obscured by glacial gravels, indicating that blind faults are present in parts of the Sourthern Alps and may be the source for a component of a reported slip deficit in North Canterbury. Concluding from comparing scaling relationship results for the individual faults I hypothesize that the Porters Pass, Hawdon, Bullock Hill and Esk faults are segments of an incipient fault system that stretches from the western tip of the Porters Pass fault to the Hope fault, east of Hanmer Springs. Considering the location, similar strike and dextral deformation mode, I suggest that this 140 km long dextral strike-slip fault system marks the southernmost extension of the Marlborough Fault System resulting from the ongoing southward propagation of the Pacific-Australian plate boundary in New Zealand's South Island.

Analogue modelling of strike-slip faulting provides insight into the development and behaviour of surface ruptures with accumulated slip, with relevance for understanding how information recorded in paleoseismic trenches relates to the earthquake behaviour of active faults. Patterns of surface deformation were investigated in analogue experiments using cohesive and non-cohesive granular materials above planar strike-slip basement faults. Surface deformation during the experiments was monitored by 3D PIV (particle image velocimetry) and 2D time lapse photography. Analysis focused on fault zone morphology and development, as well as the relationship of the models to surface deformation observed at the Greendale Fault that resulted from the 2010 Darfield earthquake. Complex rupture patterns with similar characteristics to the Greendale Fault (e.g. en echelon fractures, Riedel shears, pop-up structures, etc.) can be generated by a simple fault plane of uniform dip, slip, and frictional properties. The specific structures and the style of their development are determined by the properties of the overburden and the nature of the material surface. The width of the zone of distributed deformation correlates closely with sediment thickness, while the width of discrete fracturing is controlled by the material properties as well as the thickness of the overburden. The overall deformation zone width increases with the growth of initial, oblique fractures and subsequently narrows with time as strain localizes onto discrete fractures parallel to the underlying basement fault. Mapping the evolution of fracture patterns with progressive strain reveals that Riedel shears, striking at 90-120° (underlying fault strike = 90°) are more frequently reactivated during multiple earthquake cycles, and are thus most likely to provide reliable paleoseismic records. This will help identify suitable locations for paleoseismic trenches and interpret trench records on the Greendale Fault and other active, strike-slip faults in analogous geologic settings. These results also highlight the tendency of trenching studies on faults of this type to underestimate the number and displacement of previous ruptures, which potentially leads to an underestimate of the magnitude potential and recurrence interval of paleoearthquakes.

The Indo-Australian Plate is actively deforming at its margins and within its interior. In south-central Australia, more than 3000 km from the closest active plate boundary, a geomorphically rugged and apparently youthful mountain range has developed, rising up to 1.1km above the adjacent flat-lying outback plains. These ‘Flinders’ and ‘Barrier’ Ranges are seismically active and bound by major reverse fault scarps with clear evidence for Plio-Quaternary displacements, implying that young and active intraplate tectonism has played a fundamental role in their development. Palaeoseismic investigations and optically stimulated luminescence (OSL) chronology indicate faulting occurred in response to a series of large magnitude (~M6.6 to M7.3) palaeo-earthquakes with recurrence intervals of ~1:20,000 to~1:80,000 yrs and long-term fault slip rates of ~50 m Myr-1. Geomorphic observations and 10Becosmogenic nuclide dating indicate surprisingly high and spatially variable rates of bedrock erosion from fault-affected catchments in the Flinders Ranges. Slowly eroding bedrock summit surfaces have been uplifted up to 12 m in the last 60,000-100,000 years relative to more rapidly eroding valley floors and bounding piedmonts, indicating Late Quaternary increases in elevation and relief in response to intraplate tectonism and erosion. However, both facies changes and sediment aggradation-dissection cycles in alluvial fan sequences are out-of-synch within dividual tectonic events, indicating that an aspect of climate (aridification, changing flood frequency-magnitude distributions) has governed the spatial-temporal distribution of range front sedimentation.

Η παρούσα διδακτορική διατριβή χωρίζεται σε έξι κεφάλαια: Στο πρώτο κεφάλαιο μελετάται η γεωλογία, τεκτονική και η σεισμική δραστηριότητα στην ευρύτερη περιοχή μελέτης. Συγκεντρώνονται όλα τα διαθέσιμα στοιχεία από προηγούμενες μελέτες και δίνεται ιδιαίτερη έμφαση στα γεωλογικά, τεκτονικά και γεωτεχνικά χαρακτηριστικά της υπό εξέτασης περιοχής. Στο δεύτερο κεφάλαιο διερευνώνται οι επιπτώσεις που θα έχει στους επιφανειακούς σχηματισμούς η δραστηριοποίηση ρηγμάτων με ή χωρίς σεισμούς στην περιοχή της διώρυγας της Κορίνθου. Οι προσομοιώσεις διάδοσης της σεισμικής διάρρηξης για κάθε μία περίπτωση πραγματοποιήθηκε με τη μέθοδο των πεπερασμένων στοιχείων, με στόχο να αποκτηθεί μία πιο σαφής εικόνα της κατανομής των παραμορφώσεων, που αναμένεται να αναπτυχθούν σαν αποτέλεσμα της διάρρηξης των συγκεκριμένων ρηγμάτων, και να προσδιοριστούν περιοχές με αναμενόμενες μέγιστες παραμορφώσεις. Στο τρίτο κεφάλαιο προσδιορίστηκαν οι πιο σημαντικές και καλά προσδιορισμένες γραμμικές σεισμικές πηγές (ενεργά ρήγματα) που είναι πιθανόν να επηρεάσουν την περιοχή της διώρυγας και υπολογίσθηκε η σεισμική επικινδυνότητα. Προσδιορίστηκαν οι μέγιστες αναμενόμενες τιμές της εδαφικής επιτάχυνσης, ταχύτητας και μετατόπισης καθώς και της έντασης Arias μια παραμέτρου που παρουσιάζει καλή συσχέτιση με σεισμικά προκαλούμενες κατολισθήσεις, για διάφορες χρονικές περιόδους. Στο τέταρτο κεφάλαιο, με τη μέθοδο των συνοριακών στοιχείων μελετάται η επίδραση που θα έχει στα πρανή της διώρυγας η πιθανή ενεργοποίηση τριών διαφορετικών σεισμικών πηγών οι οποίες εντοπίζονται στην ευρύτερη περιοχή, με βασικό στόχο τον προσδιορισμό πιθανών θέσεων εκδήλωσης αστοχιών και κατ' επέκταση τον προσδιορισμό της πιο δυνητικά επικίνδυνης σεισμικής πηγής. Στο πέμπτο κεφάλαιο περιγράφεται η κατασκευή μιας ράβδου ακουστικής εκπομπής που προτείνεται για την συνεχή παρακολούθηση τμημάτων των πρανών της διώρυγας με αυξημένο πρόβλημα πιθανών καταπτώσεων. Παρουσιάζονται τα αποτελέσματα της επεξεργασίας και ανάλυσης ακουστικών εκπομπών από τις εργαστηριακές δοκιμές της ράβδου και προτείνεται ένα πλήρες σύστημα παρακολούθησης όσον αφορά την παρακολούθηση κατολισθητικών φαινομένων στη Διώρυγα της Κορίνθου. Στο τελευταίο κεφάλαιο παρατίθενται τα συμπεράσματα της παρούσας διδακτορικής διατριβής, προσδιορίζονται συγκεκριμένες θέσεις στη Διώρυγα της Κορίνθου με αυξημένο πρόβλημα εμφάνισης κατολισθητικών φαινομένων, προτείνονται λύσεις αντιμετώπισης του προβλήματος. Τέλος γίνονται προτάσεις για το πως πρέπει να συνεχιστεί η έρευνα και η αξιοποίηση των αποτελεσμάτων. / -

L’Arménie se situe dans la zone de collision entre Arabie et Eurasie et est le siège d’une déformation intracontinental active comme l’atteste les nombreux tremblements de terre historiques qui s’y sont produits. Tous ces séismes, destructeurs, attestent d’une forte activité sismique régionale, et il est par conséquent important d'évaluer l’aléa sismique associé aux structures actives qui génère cette sismicité.Le travail présenté ici, expose les résultats de l’analyse de la tectonique active au niveau des terminaisons nord-ouest et sud-est de la faille de Pambak-Sevan-Syunik (PSSF), une des failles décrochant majeure qui traverse l'Arménie du NW au SE. La quantification des déformations en termes de géométrie, cinématique, vitesse de glissement et paléosismicité, en utilisant les méthodes de datation 3He cosmogénique, OSL/IRSL et radiocarbone, révèlent des comportements différents entre les deux régions.Au niveau de la terminaison nord-ouest, dans la région d’Amassia, la faille PSSF s’incurve vers l'ouest et se subdivise en deux branches de direction WNW-ESE, et de cinématique inverse, définissant une structure en pop-up. Nous estimons une vitesse de soulèvement de 0.5 ± 0.1 mm/an et une vitesse de raccourcissement NNE-SSW de 1.4 ± 0.6 mm/an. Ces résultats suggère que l’essentiel des ~2 mm/an de mouvement dextre estimés le long de la faille de PSSF sont absorbés au niveau du pop-up d’Amassia.Au niveau de la terminaison sud-est, dans la région du volcan Tsghuk, la faille PSSF semble disparaitre. Le peu d’activité tectonique est caractérisée par des failles normales sub-méridiennes associées à une légère composante décrochant dextre. Nous déterminons une vitesse de glissement vertical de ~0,2 mm/an, une vitesse d’extension ~EW de ~0,1 mm/an associée à une composante dextre de ~0,05 mm/an. Ces résultats suggèrent que le mouvement dextre observé le long de la faille de PSSF plus au nord, a été transféré sur d'autres failles plus à l'ouest dans le Karabakh (faille Hagari ou autres structures situés encore plus au NW). / The territory of Armenia was located in the collision zone between Arabia and Eurasia, and is the seat of active intercontinental deformations, which was attested by the many historical earthquakes that have occurred in this region. All these destructive earthquakes show a strong regional seismic activity, and therefore it is important to evaluate the seismic hazard associated with active structures that generates this seismicity.This study presents the results of the analysis of the active tectonics within the northwestern and southeastern extensions of the Pambak-Sevan-Syunik fault (PSSF), a major right-lateral strike-slip fault cutting through Armenia (NW - SE). Quantifying the deformations in terms of geometry, kinematics, slip rates and earthquake activity, using cosmogenic 3He, OSL/IRSL and radiocarbon dating techniques, reveal different behaviors between the two regions.Within the northwestern extension, in the region of Amassia, the PSSF bends to the west and splits into two main WNW-ESE trending reverse faults defining a compressional pop-up structure. We estimate an uplift rate and a shortening rate of 0.5 ± 0.1 mm/y and 1.4 ± 0.6 mm/y, respectively. This suggests that most of the ~2 mm/y right lateral movement of the PSSF seems to be absorbed within the Amasia pop-structure.Within the southeastern extension, in the region of Tsghuk volcano, the PSSF shows signs of dying out at the southernmost tip of the Syunik graben. A very slow NS trending normal faulting associated with a slight right-lateral movement characterizes the tectonic activity in the region of Tsghuk volcano. We estimate vertical slip rates, EW stretching rate, and right-lateral slip rate of ~0.2 mm/y, ~0.1 mm/y and ~0.05 mm/y, respectively. These results lead to the conclusion that the right lateral movement observed further north along the PSSF is mainly transferred within other active faults further west within the Karabagh (Hagari fault or other structures further northwestwards).

L’histoire et les mécanismes de soulèvement des Andes centrales ont fait l'objet de débats animés depuis les années 1970. Notre étude se concentre sur l’analyse de la déformation Cénozoïque et de l'exhumation des Andes Centrales dans la région du Sud Pérou : à Cuzco, et dans la région de Nazca entre les cordillères Occidentale et Côtière. En effet, plusieurs auteurs soulignent le rôle du raccourcissement tectonique dans l'épaississement de la croûte, dans l’avant-arc Chilien ou à l’Est dans la région Subandine. Dans les modèles de déformation tectonique active issus du GPS, aucun raccourcissement ni transpression n’est pris en compte sur la bordure Occidentale des Andes au Cénozoïque ou dans les modèles de déformation crustale issus du GPS. La nouvelle cartographie des systèmes de failles actives dans la région sud du Pérou donnent un aperçu de la déformation active à l’échelle crustale pour la marge Pacifique des Andes Centrales. La géomorphologie et les paysages de l'avant-arc andin ont classiquement été présentés comme fossiles depuis le Miocène, sans évidence de structures actives accommodant la déformation cénozoïque. Cependant, les surfaces géomorphologiques bien préservées développées dans l'avant-arc du sud du Pérou fournissent d'excellents marqueurs et des évidences de déformation très nettes depuis le Cénozoïque jusqu’au Quaternaire récent. Ces marqueurs montrent tous un soulèvement des Andes le long de la marge ouest depuis les derniers Millions d’années. Bien que l’initiation et l’évolution de l'exhumation et du soulèvement cénozoïque aient été étudié dans les canyons de Colca et de Cotahuasi, il demeure peu contraint dans le segment nord de l'avant – arc, i.e., dans la région de Nazca. Dans cette étude, nous avons choisi d’apporter de nouvelles données (U-Th)/He et traces de fission sur apatite (AHe) et (AFT) respectivement dans cette région. L’échantillonnage a porté sur la Cordillère Occidentale entre Cañete et Nazca le long de deux nouvelles coupes transversales à la topographie. Le profil Age/Distance à la côte indique une mise en place de relief dans la région Andine au début du Miocène et une évolution découplée des deux systèmes de cordillères Cotière et Occidentale en terme d’exhumation dans le temps. A l’échelle Quaternaire, nous avons cartographié les failles actives pour déterminer leur géométrie, cinématique et les âges maximaux de l’activation de ces failles. Ceci afin de discuter du rôle de cette activité tectonique, précédemment supposée Miocène, dans le soulèvement et l’exhumation de l’avant-arc Andin. Nous avons utilisé la production et l’accumulation du 10Be cosmogénique dans les roches pour déterminer les âges d'exposition d’un escarpement tectonique marquant les derniers épisodes co-sismiques de la faille de Purgatorio. Nos nouveaux résultats, contrastent avec des conclusions précédentes qui concluaient à de l’extension et des vitesses lentes le long de l’avant arc Andin (<0.1mm/an). Les âges très récents indiquent une morphologie « historique » (free face) et deux tremblements de terre Mw6-7 sur ce système de failles transpressives qui se connectent au système principal d’Incapuquio. Les données suggèrent non seulement une déformation active significative de l’avant-arc, mais soulignent aussi l’existence d’un aléa sismique qui n’est toujours pas pris en compte pour les failles crustales dans les Andes. Tandis que l’hypothèse acceptée est que la déformation active est localisée dans le bassin d’avant pays subandin, ou à l’est de la cordillère orientale, nos données suggèrent qu’une partie de la déformation active se localise aussi sur la marge Occidentale ainsi que le long de la faille d'Incapuquio. De plus, les failles observées en néotectonique accommoderaient le partitionnement de la déformation le long de la subduction oblique et ceci n’a jamais été discuté précédemment. Ce mouvement, rigide, en bloc serait du à la présence du craton accrété sur le flanc Ouest et à sa rigidité. / ABSTRACTTiming and mechanisms of uplift in the Central Andes have been a matter of debate since at least the 1970’s. Our study focuses on Cenozoic deformation and exhumation of the Central Andean forearc in Peru, in Cuzco region, and between the Western Cordillera and the Coastal Cordillera in Nazca region. Our new mapping of active faults provides new insights into the Cenozoic to present-day crustal deformation of the Central Andean Western margin. Until now, apart from some local studies, the geomorphology of the Andean forearc has classically been presented as a remnant Miocene landscape with no significant active structures accommodating the Cenozoic deformation. Thanks to new high-resolution optical imagery, the well-preserved geomorphic surfaces developed within the forearc of southern Peru provide excellent regional markers to map patterns of deformation. Pertaining to the Cenozoic history, while the timing of uplift-related exhumation and Cenozoic exhumation has been studied in Colca and Cotahuasi canyons, it remain poorly constrained in the northern segment of the Central Andean forearc. I report new apatite (U–Th)/He (AHe) and fission track (AFT) ages from the western Cordillera between Cañete and Nazca along two new cross sections. The ages in Nazca region reflect relatively recent (since ~10Ma) relief creation along the western margin of the Altiplano, similar to what is described south in Colca region.The Quaternary tectonic history is revealed by the newly mapped fault segments affecting the Miocene deposits within forearc. Through field and remote mapping, I determined fault geometries and maximum ages for the activity of the faults systems based on stratigraphic relationships in order to assess the role of this tectonic activity in the Western Cordillera uplift and exhumation.To understand the Holocene tectonic history, we use in situ produced 10Be to determine the exposure ages of the free face and tectonic scarp of the Purgatorio Fault in order to map the temporal evolution of its seismotectonic activity. Our new results display evidence of transpression and the formation of meter-high coseismic scarps as well as very recent exposure ages indicating a youthful fault morphology and Mw6-7 earthquakes occurring along the Purgatorio fault segments. These new data are in contrast with some previous conclusions for this region which suggest extension and/or slow rates of deformation for this region and time period. Further, these new data not only suggest significant active deformation within the forearc, but also highlight a potential seismic hazard for the region that not take into account crustal forearc faults.While the general assumption is that active deformation is localized in the Subandean fold and thrust belt, or east of the Western Cordillera in the Altiplano, our data support a model where active deformation is occurring in the western margin as well, along the Incapuquio Fault and other neotectonic faults that accommodates the partitioning of the subduction oblique convergence.These crustal active faults and more precisely the “not migrating to the trench” Incapuquio fault zone reveal the rigid motion of the forearc. Our new model is nevertheless compatible with the recently published GPS data that measure a southeastward movement at 4–5 mm/yr relative to a stable South America reference frame. This rigid motion is in part due to the presence of the rigid Greenvillian accreted craton, that behave as a sliver, and rather tilt than deform through time.

La chaîne Himalayenne est l'un des exemples les plus spectaculaires de déformation active à la surface de notre planète. Au cours des derniers siècles, de nombreux séismes majeurs (Mw > 7.5) ont affecté cette zone et le lourd bilan humain du séisme de Gorkha en 2015 a une nouvelle fois rappelé l’importance de parvenir à mieux estimer l’aléa sismique de cette région. Bien que les structures lithologiques et tectoniques semblent montrer au premier ordre une cylindricité le long des 2500 km de l'arc Himalayen, de nombreuses études, menées principalement au Népal, ont permis de mettre en évidence des variations latérales structurales, thermochronologiques, morphologiques, gravimétriques, sismologiques ou géodésiques. Le rôle de ces variations latérales sur la segmentation sismique reste cependant mal contraint. La taille maximale et la probabilité d’occurrence de ces méga-séismes sont donc toujours matière à débat.Ainsi, le comportement sismique de l’Himalaya du Bhoutan reste énigmatique. Pour certains les faibles taux de sismicité observés actuellement font de ce royaume une zone asismique de 350 km de long. Pour d’autres, à l’instar de l’Himalaya du Népal, la faible sismicité observée est associé à une forte accumulation de contrainte susceptible de générer des séismes majeurs. L'objectif de ce travail de thèse est d’améliorer notre connaissance de cette région en quantifiant la déformation à différentes échelles spatiales et temporelles via des études morphotectoniques et paléosismologiques.La première partie de cette thèse vise à quantifier les mouvements verticaux à l’ouest Bhutan et le long du Main Frontal Thrust, structure la plus frontale située au sud Bhoutan. Trois campagnes de terrain ont été réalisées permettant l'échantillonnage (1) de terrasses alluviales le long du front afin de quantifier et d'étudier les variations du soulèvement Holocène, (2) de bassins versants pour l'étude de la dénudation court-terme (< 20 ka) dérivée des cosmonucléides ($^{10}$Be) et (3) de terrasses alluviales dans le Moyen-Pays pour quantifier l’incision Holocène. Les vitesses verticales obtenues au front sont comparables à celle proposées le long du reste de l’arc himalayen, suggérant une cinématique relativement simple. Par contre, nos résultats indiquent une variation de la géométrie du chevauchement himalayen (Main Himalayan Thrust) entre l’est Népal et l’ouest Bhoutan.La seconde partie porte sur plusieurs études paléosismologiques le long du front ouest et centre Bhoutanais. Six sites différents ont été étudiés au cours de trois campagnes de terrain. La datation et la modélisation de charbons détritiques a permis de mettre en évidence l'occurrence d’au moins cinq séismes majeurs durant les derniers 2700 ans, faisant du Bhoutan une zone sismiquement aussi active que le Népal. A une échelle régionale, cette étude apporte donc de nouvelles contraintes et contribue au débat sur la possibilité d’occurrence d'un séisme de magnitude 9 le long de l'arc Himalayen. / The Himalayan arc is one of the most active intra-continental mountain belts in the world. Over the last centuries, several major earthquakes (Mw > 7.5) have struck this arc. The dramatic effects of the Gorkha earthquake sequence in 2015 pointed once again the crucial need to improve seismic hazard assessment of this area.Geological explorations of the Himalayas since the late 19th century have emphasized a 2500-km-long roughly cylindrical structure, with striking continuity of main units and thrust faults. However recent geophysical and geological investigations have revealed lateral variations. The relationship between these variations and earthquakes segmentation along the arc remains poorly constraint. The maximum size and the occurrence probability of such earthquakes are still a matter of debate.For instance, the seismic behavior of Bhutan remains enigmatic. The present-day low seismicity rate observed in this area can reflect two opposite fault behaviors: an aseismic creeping zone or a zone of stress accumulation for future great earthquakes as the others parts of Himalayas. The main objective of this thesis is to bring new constraints on the deformation of the Bhutan Himalayas, at different space- and time-scales, through morphotectonic and paleoseismological approaches.The first part of this thesis focuses on the vertical deformation assessment along a N-S transect in western Bhutan and along the Main Frontal Thrust, which is the southern-most thrust in southern Bhutan. In the past three years, we have carried out three fieldwork campaigns to sample (1) frontal terraces to assess Holocene uplift rates, (2) watershed basins to quantify short term denudation rates (< 20 ky) derived from cosmonuclides $^{10}$Be and (3) hinterland alluvial terraces to quantify the Holocene incision rate. Frontal Holocene uplift rates obtained in Bhutan are consistent with those obtained in the others parts of Himalayas. Furthermore, our results reveal a variation in the geometry of the Main Himalayan Thrust between eastern Nepal and western Bhutan.The second part focuses on several paleoseismic studies along the west and central bhutanese Himalayan front. Different sites were investigated during three fieldwork campaigns. Detritic charcoals sampling and modeling suggest the occurrence of at least five surface-rupturing earthquakes during the last ~2700 years. These results demonstrate that the present-day low seismicity rate observed in Bhutan is not representative of the seismic activity at longer time scale. At regional scale, they also take part of a broader discussion on the probability of occurrence of a magnitude 9 earthquake along the Himalayan arc.

Au Nord-Est de la microplaque Adriatique la jonction Alpes-Dinarides représente une région clé pour comprendre les interactions entre la microplaque et l’Europe stable. Alors que la tectonique active de la partie alpine de cette zone est relativement bien contrainte, peu de données sont disponibles quant aux déformations actives contrôlées par la rotation de la microplaque à travers les Dinarides. Par une approche morpho-tectonique (étude de terrain combinée à l’analyse d’images aériennes et satellitaires, de cartes topographiques et modèles numériques de terrain haute résolution) nous avons cartographié en détails les failles actives des Dinarides septentrionales et de la partie orientale des Alpes du Sud. Sur la base de cette cartographie et des données géologiques une quarantaine de décalages tectoniques cumulés allant de quelques mètres à plusieurs kilomètres a été identifiée. A l’aide de datations 36Cl de marqueurs morphologiques affectés par les failles combinées aux chronologies existantes les vitesses de déformation actuelles ont ensuite été estimées. L’évolution des déformations depuis le Pliocène a pu être contrainte dans les Dinarides mettant en évidence une initiation des failles au début du Pliocène et un changement cinématique important autour du Pléistocène moyen. Les vitesses obtenues, notamment environ 3mm/an de mouvement dextre le long des Dinarides, ont finalement été confrontées aux modèles existants ce qui a conduit à proposer un modèle cinématique décrivant l’accommodation de la rotation de l’Adriatique par le mouvement relatif de blocs lithosphériques rigides et qui permet d’expliquer les déformations actives observées aux frontières de ces blocs. / At the northeastern corner of the Adria microplate the Alps-Dinarides junction represents a key region to understand the interactions between the microplate and the stable Europe. While the active tectonics of the alpine part of the area is relatively well-known, few data allow characterizing the present-day deformations controlled by the microplate rotation across the Dinarides. Using a morpho-tectonic approach (field study combined to the analysis of aerial and satellite images, topographical maps and high-resolution digital elevation models) we mapped in details the active faults in the Northern Dinarides and the eastern part of the Southern Alps. Based on this mapping and geologic data forty tectonic cumulative displacements ranging from few meters to several kilometers have been identified. By determining the 36Cl exposure ages of faulted geomorphic markers and comparing it to existing chronologies the present-day rates of deformation have then been assessed. The evolution of the deformations since the Pliocene could also have been constrained revealing an Early Pliocene age for the onset of strike-slip faulting and a major kinematic change during the Middle Pleistocene. Finally the yielded faults slip-rates, especially about 3 mm/yr of right-lateral motion across the Dinarides, have been compared to existing models. That allowed proposing a kinematic model describing the Adria rotation accommodation through the relative motion of rigid lithospheric blocks and explaining the observed active deformations at their boundaries.

The geomorphic expression, sedimentation, and near-field deformation of a fault system may be characterized to obtain an understanding of its kinematic evolution and potential seismic hazards. The dynamics and deformation history of the Eastern California shear zone (ECSZ), a wide and complex network of right-lateral strike-slip faults, is not well understood, despite hosting three large (>Mw 7.0) earthquake ruptures in recent decades. The low-net slip faults of the ECSZ (each with <10 km) offer a unique opportunity to assess strain distribution in a developing, kinematically immature strike-slip system. To do so, I conducted field-based investigations of these faults within the Mojave Block of the ECSZ. First, I investigated the morphology, structure, and controls of restraining bend growth along the numerous faults of the ECSZ via field mapping and numerical deformational modeling. I found that the ECSZ restraining bends are small (kilometer-scale), exhibit high-angle, doubly fault-bound geometries with positive flower structures, and have self-similar morphologies characterized by a "whaleback" longitudinal profile and an arrowhead shape in map view. Gradual changes in form with increasing restraining bend size suggest a common growth mechanism influenced more by the kinematics of local fault geometries than by the fault's obliquity to plate motion. Modeling results indicate that concentrated shear strain at single transpressional bends facilitates the development of new secondary faults with cumulative strain as a mechanism to accommodate horizontal shortening via uplift between the faults. The ECSZ restraining bends contribute minimally to regional contractional strain due to their small size, steep fault angles, and shallow crustal penetration (< 5 km), which also suggests that they are unlikely to obstruct large earthquake ruptures. Second, I conducted a spatiotemporal slip rate analysis of the Calico fault with new mapping and geochronology of offset alluvial fans from North Hidalgo Mountain. From this work I obtain several findings. 1) The slip rate along North Hidalgo Mountain ranges from 1.5-2.1 mm/yr in the Holocene and 0.8-2.0 mm/yr in the late Pleistocene. 2) The similarity in slip rates between North Hidalgo Mountain and the Rodman Mountains suggests that this 38 km stretch is a kinematically coherent fault segment with a relatively steady slip rate of 1.7 +0.4/-0.3 mm/yr over the past 60 ka. Faster rates reported from Newberry Springs suggest either a significant increase in slip rate from the Rodman Mountains to Newberry Springs or temporal variations in slip rate. 3) The new rates support previous work which showed the central section of the Calico fault has the highest slip rate in the Mojave Block. However, it does not resolve the discrepancy between ECSZ geodetic and geologic slip rates, implying that transient changes in slip rate, or the contribution of off-fault deformation or other structures may be required. Additionally, the lack of geological slip rate data might contribute to this discrepancy if significant spatial and temporal variations exist on other ECSZ faults. / Doctor of Philosophy / The topography and geology within a fault system may be studied to understand tectonic plate motion over time and assess earthquake hazards. The Eastern California shear zone is a complex network of strike-slip faults within the Mojave Desert, which has hosted three large earthquakes (>Mw 7.0) in recent decades. Despite this significant seismic activity, the mechanisms of motion across the numerous faults in the Eastern California shear zone remain poorly understood. The individual faults have accumulated relatively little strike-slip motion since their inception (less than 10 kilometers), offering a unique opportunity to investigate the early-stage kinematics and seismic hazards of a strike-slip fault system. To do so, I conducted field-based investigations of the faults within the Eastern California shear zone. First, I investigated the early evolution and controls of compressional strike-slip fault bends in the Eastern California shear zone. From mapping and numerical modeling, I characterized the shape, structure, and uplift of numerous small compressional bends dispersed across the faults. From these efforts, I found that uplifted crust in the fault bends exhibit self-similar forms with shallow crustal depths (<5 km). Small changes in the shape of these structures occur with increasing size indicating a predictable pattern of growth with increasing cumulative slip that appears to be partially controlled by local fault conditions. Numerical modeling of simple compressional fault bends indicate that shear strain concentrates at bend corners, which may facilitate the growth of a new fault that more efficiently accommodates contraction in the bend via uplift of the crust between the two faults. The compressional strike-slip fault bends in the Eastern California shear zone are too small to significantly impact regional contractional strain and are therefore also unlikely to impede large earthquake ruptures. Second, I studied the slip rate (or rate at which the fault moves) of the Calico fault via new mapping and age data of displaced alluvial fans. I found that 1) the Calico fault at North Hidalgo Mountain slips at a rate of 0.8-2.0 mm/yr since ~70,000 years ago. 2) The slip rates from North Hidalgo Mountain and the Rodman Mountains are similar, indicating that the 38 kilometers between them behaves consistently, with a steady rate of ~1.7 mm/yr over the last ~60,000 years. However, faster slip rates reported at Newberry Springs suggest either a significant increase in slip rate from the Rodman Mountains to Newberry Springs or that it varies over time. 3) These findings confirm that the central Calico fault has the fastest slip rate in the Mojave Block but does not reconcile regional differences between rates from geodetic and geological measurements. The difference between the slip rates measured by geodetic methods and those from geological studies in the Eastern California shear zone suggests that there could be temporary changes in slip rates or that deformation might be occurring in areas away from the main fault. Also, the lack of geological slip rate data might contribute to this discrepancy if significant spatial and temporal variations exist on other Eastern California shear zone faults.