The earth was shown in the last century to have a surface layer composed of large plates. Plate tectonics is the study of the movement and stresses in the individual plates that make up the complete surface of the world's sphere. Two types of earthquakes are observed in the surface plates, interplate and intraplate earthquakes, which are classified, based on the location of the origin of an earthquake either between two plates or within the plate respectively. Limited work has been completed on the definition of the boundary region between the plates from which interplate earthquakes originate, other than the recent work on the Mid Atlantic Ridge, defined at two degrees and the subsequent work to look at the applicability of this degree based definition. Others suggested an alternative view of a constant width for the interplate region in recent work at Texas A&M University. The objective of the paper is to determine whether the assumption of a linear width of the region along the tectonic plate boundaries to classify earthquakes as interplate and intraplate earthquakes using accepted statistical criteria provides a better fit to the data than the constant degree definition. There are three types of interplate boundaries defined by the relative movement of the two plates to each other, which further complicates this study. The study used a nonrandom analysis of regions of the different types of boundary to compare the rate and decay of the intraplate earthquakes from a notional centerline for the known boundaries. The study used GIS software and EXCEL for the statistical analysis component of the research work. The results show that a constant width definition provides a number of advantages in determining the relative definition of interplate and intraplate earthquakes when compared to the constant degree definition developed for work on the Mid Atlantic Ridge. Further research is suggested on a randomly selected set of study sites to improve the reliability and quality of the statistical work for each type of the boundary of the tectonic plates.

The Lyttelton Volcanic Complex, north-western Banks Peninsula, New Zealand, is comprised of five overlapping volcanic cones. Two magma systems are postulated to have fed Banks Peninsula’s basaltic intraplate volcanism, with simultaneous volcanism occurring in both the north-western and south-eastern regions of Banks Peninsula, to form Lyttelton and Akaroa Volcanic Complexes respectively. The elongate form of Banks Peninsula is postulated to relate to the upward constraining of magmatism in a north-west / south-east fault bounded zone. The Lyttelton Volcanic Complex resulted from the development of a pull-apart basin, with a number of releasing bend faults, controlling the location of eruptive sites. Cone structure further influenced the pathway magma propagated, with new eruptive sites developing on the un-buttressed flanks, resulting in the eruption and formation of a new cone, or as further cone growth recorded as an eruptive package. Each cone formed through constructional or eruptive phases, termed an eruptive package. Eruptive packages commonly terminate with a rubbly a’a to blocky lava flow, identified through stratigraphic relationships, lava flow trends and flow types, a related dyking regime, and radial erosional features (i.e. ridges and valleys). Within the overall evolving geochemical trend of the Lyttelton Volcanic Complex, are cyclic eruptive phases, intrinsically linked to eruptive packages. Within an eruptive package, crystal content fluctuates, but there is a common trend of increasing feldspar content, with peak levels corresponding to a blocky lava flow horizon, indicating the role of increased crystalinity and lava flow rheology. Cyclic eruptive phases relate to discreet magma batches within the higher levels of the edifice, with crystal content increasing as each magma batch evolves, limiting the ability of the volcanic system, over time, to erupt. Evolving magmas resulted in explosive eruptions following effusive eruptives, and / or result in the intrusion of hypabyssal features such as dykes and domes, of more evolved compositions (i.e. trachyte). Each eruptive package hosts a radial dyke swarm, reflecting the stress state of a shallow level magma chamber or a newly developed stress field due to gravitational relaxation in the newly constructed edifice, at the time of emplacement. Two distinct erosional structures are modelled; radial valleys and cone-controlled valleys. Radial valleys reflect radial erosion about a cone’s summit, while cone-controlled valleys are regions where eruptive packages and cones from different centres meet, allowing stream development. Interbedded epiclastic deposits within the Lyttelton lava flow sequences indicate volcanic degradation during volcanic activity. As degradation of the volcanic complex progressed, summit regions coalesced, later becoming unidirectional breached, increasing the area of the drainage basin and thus the potential to erode and transport extensive amounts of material away, ultimately forming Lyttelton Harbour, Gebbies Pass, and the infilled Mt Herbert region. Epiclastic deposits on the south-eastern side of Lyttelton Harbour indicate a paleo-valley system (paleo-Lyttelton Harbour) existed prior to 8.1 Ma, while the morphology of the Lyttelton Volcanic Complex directed the eruptive sites, style and resultant morphology of the proceeding volcanic groups.

In intraplate seismic zones (e.g. the New Madrid Seismic Zone, NMSZ, in the southcentral United States), the source of stress that drives earthquake is very complex. Data from the NMSZ indicate 3 earthquake of magnitude M~7, occurring at an approximate interval of 500 years during the last 2000 years. One hypothesis that satisfies these conditions proposes that short-lived bursts of earthquakes may result from perturbations in the local or regional stress field. This causes relaxation of a lower crustal weak zone which drive repeated earthquakes. The number of earthquakes is dependent on the geometry and rheology of the weak zone. Using finite element techniques which employ contact surfaces to model discrete faulting events and a maximum shear stress criteria evaluated at each node. We investigate the relevant parameter space, as it affects the concentration of stress at the base of the seismogenic fault and the number of earthquakes generated over a given time interval. Parameters that can be varied include earthquake stress drop, background tectonic stress, and maximum shear stress at failure. Results show that solutions are non-unique. With the addition of existing observational evidence, however, we can place bounds on the range of parameters which satisfy above observations.

The Cottage Grove Fault System is an East-West trending system of strike slip faults within Southern Illinois that has been explored for mineral resources but never systematically examined for seismicity or seismic hazard. Due to its location between the seismically active Wabash Valley, Saint Genevieve, and the New Madrid Seismic Zones, and the prevalence of nearby structural features, this fault system merits its own systematic study. Using existing data from the EarthScope Transportable Array, seismic activity and implications for hazard are explored through microseismicity. Over a two-year period, the closest two seismometers to the CGFS were utilized to search for microseismicity along the fault. Analysis was done through visually assessing waveforms and frequency-amplitude plots, which can help differentiate mine blasts and earthquakes based on the frequency content of the waveform. During the 2-year deployment, a total of 94 seismic events were detected, with 5 previously unrecorded earthquakes located within the Cottage Grove Seismic Zone, although none were located on the main fault. The greatest magnitude of the Cottage Grove Fault System events found was an M_L 1.5 and the smallest an M_L 0.8. The methodology found all seismic events mb 2.3 or greater listed by the Center for Earthquake Research and Information (CERI) catalog, within a 150 km radius. Missed events from the CERI catalog were small and distant. Finding earthquakes near the Cottage Grove Fault System undetected by the CERI network demonstrates that the region has a degree of previously undetected seismic activity. Preliminary event detection is better explained by a b-value of 0.7 than a b-value of 1.0, suggesting current estimates of the hazard of the CGFS is underestimated.

Intraplate volcanism is a worldwide phenomenon producing volcanoes away from active plate boundaries, a process that cannot yet be sufficiently explained by plate tectonic processes, and thus is still a missing piece in the understanding of the dynamics and evolution of our planet. Models for the formation of intraplate volcanism are dominated by mantle plumes, but alternative explanations, such as adiabatic decompression triggered by lithospheric delamination, and edge driven convection (EDC), could be responsible for magmatism. This dissertation explores intraplate volcanic locations that do not fit the mantle plume model, and presents geochemical evidence for lithospheric delamination and edge driven convection for the cause of volcanism. I studied an Eocene volcanic swarm exposed in the Appalachian Valley and Ridge Province of Virginia and West Virginia, which are the youngest known igneous rocks along the Eastern North American Margin (ENAM). These magmas provide the only window into the most recent deep processes contributing to the post-rift evolution of this margin. This study presents the first high precision 40Ar/39Ar ages along with new geochemical data, and radiogenic isotopes that constrain the melting conditions and the timing of emplacement. Modeling of the melting conditions suggests that melting occurred under conditions slightly higher than average mantle beneath mid-ocean ridges. Asthenosphere upwelling related to localized lithospheric delamination is a possible process that can explain the intraplate signature of these magmas that lack evidence of a thermal anomaly. The Virginia-West Virginia region of the ENAM also preserves a second post-rift magmatic event in the Late Jurassic. By studying both the Late Jurassic and Eocene magmatic events we can better understand the post-rift evolution of passive margins. This study presents a comprehensive set of geochemical data that includes new 40Ar/39Ar ages, major and trace-element compositions, and analysis of radiogenic isotopes to further constrain their magmatic history. Modeling suggests that the felsic volcanics from both the Late Jurassic and Eocene events are consistent with fractional crystallization. Lithospheric delamination is the best hypothesis for magmatism in Virginia/West Virginia, due to tectonic instabilities that are remnant from the long-term evolution of this margin, resulting in a 'passive-aggressive' margin that records multiple magmatic events long after rifting ended. Finally, Bermuda is an intraplate volcano that has been historically classified as mantle plume related but evidence to support the plume model is lacking. Instead, geophysics have argued that EDC is the best model to explain Bermuda volcanism. This study presents the first geochemical analysis of Bermuda volcanism, and found that Bermuda was built by two different magmatic processes: melting of carbonated peridotite to produce silica under-saturated, trace element enriched volcanics and melting of an enriched upper mantle component that produced silica saturated volcanics. We attribute the cyclicity of silica under-saturated and silica saturated volcanics to EDC melting. / Ph. D.

Seismic hazard calculations for sites in eastern North America have traditionally assumed a Poisson process to describe the temporal behavior of earthquakes and have employed the Gutenberg-Richter relationship to define the frequency distribution of earthquake magnitude. For sites in areas where geological information indicates recurrent, large earthquakes, however, such data imply a rate for large events which often exceeds that predicted by the Gutenberg-Richter relationship. One way in which this discrepancy can be reconciled is to assume that the larger events occur as a time-dependent, or renewal, process and possess a "characteristic earthquake" magnitude distribution. The main purpose of this study is to make a quantitative comparison of seismic hazard estimates for Charleston of the influences of 1) the Poisson temporal model assuming the Gutenberg-Richter and characteristic earthquake magnitude recurrence relationships with 2) the renewal temporal model assuming the characteristic magnitude recurrence relationship. Other issues that are examined are the sensitivity of uncertainties of hazard model parameters such as maximum magnitude and seismic source delineation. Probabilistic seismic hazard calculations for the next 50 years were performed at Charleston for all potential seismic sources. The highest estimate of seismic hazard was obtained with the Poisson temporal model and characteristic earthquake recurrence relationship. The lowest hazard was obtained with the renewal temporal model and characteristic magnitude recurrence relationship. The results of this study are in good agreement with hazard estimates for Charleston in the most recent national seismic hazard maps. / Master of Science

Essa tese de Doutorado tem por objetivo apresentar uma discussão sobre a evolução do manto litosférico subcontinental na região nordeste da Província Borborema, desde o Mesozóico até Cenozóico. Para isso foram obtidos dados de geoquímica elementar e isotópica de dois importantes eventos magmáticos expostos na região: (i) o enxame de diques toleíticos Ceará-Mirim (Cretáceo Inferior) e (ii) o vulcanismo alcalino Macau representado por plugs, necks e lavas com idades distribuídas desde o Oligoceno ao Mioceno.O enxame de diques de Ceará Mirim é composto de (i) olivina toleítos de alto-Ti, (ii) toleítos evoluídos de alto-Ti (TiO2>1,5 wt.%; Ti/Y>360), e (iii) toleítos de baixo-Ti (TiO2<1,5wt%; Ti/Y<360), todos com forte enriquecimento em elementos incompatíveis relativo ao manto primitivo. Os olivina toleitos exibem teores em Nb-Ta semelhante àqueles de magmas do tipo OIB. Ao contrário, os toleitos evoluídos de alto-Ti e os toleítos a baixo-Ti mostram anomalias negativas em Nb-Ta, as quais são mais pronunciadas nos basaltos de baixo-Ti. Os olivina toleítos mostram a razões iniciais 87 Sr/86Sr uniformes (0,7034-0,7037), enquanto que as composições isotópicas de Nd e Pb são variáveis, parte delas moderadamente radiogênicas(0,512518- 0,512699; 19,13-19,25). As composições isotópicas de Pb sugerem a contribuição de um componente FOZO na gênese desses olivina toleitos. Os outros toleítos apresentam valores muito mais variáveis, com 87Sr/86Sr radiogênicas (em comparação ao BSEt=127) e valores subcondríticos para Nd (<0,512442 ou \'épsilon\'Nd< -0,6). Quando combinadas com razões 206Pb/204Pb entre 17,08 e 18,41, os toleitos evoluídos de alto-Ti e os toleitos de baixo-Ti mostram afinidade com o componente EMI, sendo as características enriquecidas dos toleitos de baixo-Ti mais acentuadas devido a contaminação crustal durante ascensão. As similaridades com EMI, as anomalia de Nb e idades modelo TDM> 1 Ga, são evidências composicionais para atribuir a origem dos toleítos evoluídos de altoe baixo-Ti à fusão do manto litosférico subcontinental proterozóico, metasomatizado por um componente de subducção. Os dados de termometria aliados aos padrões fracionados de elementos terras raras indicam que a fusão deve ter acontecido a ~60 km,na região de transição granada-espinélio assumindo uma litosfera afinada durante o Cretáceo. Os olivina toleitos, por sua vez, teriam fundido em profundidades de ~75 km a partir da astenosfera tipo-FOZO, passivamente soerguida em decorrência de afinamento litosférico relacionado a esforços distensivos duranteo Cretáceo. O vulcanismo cenozóico Macau é representado por alcali-basaltos, basanitos e nefelinitos. Basaltos toleíticos são menos comuns. Em geral, os basaltos Macau guardam alguma semelhança com os olivina toleitos cretáceos. São enriquecidos em elementos incompatíveis e 6 em Nb-Ta, mas com características mais primitivas como10<MgO<15wt.% e 200<Ni<500ppm. Todos experimentaram fracionamento de olivina e clinopiroxênio, enquanto plagioclásio contribuiu em menor importância. O modelamento feito a partir de razões entre elementos terras raras combinado a dados termométricos indicam que os basanitos e alcali-basaltos teriam fundido a partir de lherzolitos a profundidade entre 80-90 km, na região de transição espinéliogranada, enquanto que os nefelinitos seriam produto da fusão (<0,1%) mais profunda,a ~120 km de profundidade (~1470ºC). As composições isotópicas Sr-Nd-Pb são semelhantes a magmas OIB gerados pela mistura de dois reservatórios, odelados como FOZO e EM. A identificação de FOZO no Cenozóico da Província Borborema aliada à ausência de um cenário tectônico compatível com afinamento litosférico/ascensão passiva da astenosfera e/ou presença de plumas,nos leva a propor que a astenosfera tipo-FOZO teria se re-equilibrado termalmente com o manto litosférico subcontinental desde o Cretáceo. Ao contrário, o componente EM nos basaltos Macau não pode ser correlacionado ao mesmo manto litosférico enriquecido identificado nos toleitos. Embora ainda não muito clara, sua origem é por ora atribuída a metassomatismo potássico provavelmente relacionado ao impacto da pluma de Fernando de Noronha sob o continente. As similaridades isotópicas entre esses basaltos oceânicos e os basaltos continentais sugerem que alguma ligação genética deve ser considerada. Por fim, composições isotópicas de Os e idades modelo TRD obtidos de xenólitos peridotíticos nos basaltos cenozóicos, registram a recorrência de múltiplos eventos de extração de magmas (1,3 a 0,1 Ga) e metassomatismo, confirmando a evolução química complexa experimentada pelo manto litosférico subcontinental no extremo nordeste da Província Borborema. / The objective of this doctoral thesis is to present a discussion on the evolution of the subcontinental lithospheric mantle in the northeast of the Borborema Province from the Mesozoic to the Cenozoic. For this reason, element and isotope geochemical data were obtained from two important magmatic events in the region: (i) the Lower Cretaceous Ceará-Mirim dyke swarm and (ii) the Macau alkaline volcanism characterized by plugs, necks and flows of Oligocene to Miocene ages. The Ceará-Mirim dyke swarm is composed of (i) high-Ti olivine tholeiites, (ii) evolved high-Ti tholeiites (TiO2>1.5 wt.%; Ti/Y>360), and (iii) low-Ti tholeiites (TiO2<1.5 wt.%; Ti/Y<360), all exhibiting strong enrichment in incompatible elements relative to the primitive mantle. The Nb-Ta abundance in the olivine tholeiites is of OIB affinity, while the evolved high-Ti and the low-Ti tholeiites demonstrate Nb-Ta negative anomalies, more accentuated in the low-Ti basalts. Initial 87Sr/86Sr ratios in the olivine tholeiites are less variable (0.7034-0.7037), but have variable Nd and Pb isotopic compositions with some moderately radiogenic (0.512518-0.512699; 19.13-19.25). The Pb isotopic compositions suggest the contribution of a FOZO component in the genesis of the olivine tholeiites. The other tholeiites exhibit more variable values, with radiogenic 87Sr/86Sr (relative to BSEt=127) and subchondritic Nd <;0.512442 or \'èpsilon\'Nd < -0.6). When combined with the 206Pb/204Pb ratios of 17.08 to 18.41, the evolve high-Ti tholeiites demonstrate EM1 affinity, with the enriched nature of the low-Ti tholeiites more enhanced due to crustal assimilation during ascent. The similarities with EM1, the Nb anomaly and the TDM model age> 1 Ga, are compositional evidence that suggest the magmas of the evolved high-Ti and low-Ti tholeiites were generated from the melting of the Proterozoic subcontinental lithospheric mantle, metasomatized by a subduction component. A combination of the inferred temperature data with the fractionated rare earth element patterns indicate that melting might have occurred at ~60km, at the garnet-spinel lherzolites transition zone in a thinned lithosphere during the Cretaceous. On the other hand, the olivine tholeiite magma might have been generated at ~75 km depth, in a FOZO-type asthenosphere that passively welled up due to the lithospheric extension and thinning in the Cretaceous. The Macau volcanism is composed of alkali basalts, basanites and nephelinites, and rare tholeiitic basalts. Generally, the Macau basalts and the Cretaceous olivine tholeiites share some similarities. They are enriched in incompatible elements and in Nb-Ta, but with more primitive characteristics like 10<MgO<15 wt.% and 200<Ni<500 ppm. All experienced fractionation of olivine and clinopyroxene, but less important for plagioclase. Rare earth element modeling and inferred temperature data indicate that the basanitic and the alkaline basaltic magmas melted from lherzolites at 80-90 km depth, at the spinel-garnet transition, while the nephelinitic magmas were generated from melting (<0.1%) at deeper levels, at ~120 km of depth (~1470°C). The Sr-Nd-Pb isotopic compositions have affinity to OIB magmas generated from the mixing of two reservoirs, modeled as FOZO and EM. The identification of FOZO in the Borborema Province in the Cenozoic with the absence of a compatible tectonic scenario such as lithospheric thinning/passive asthenospheric upwelling and/or the presence of plumes, make us to propose that a FOZO-type asthenosphere might have thermally re-equilibrated as a subcontinental lithospheric mantle since the Cretaceous. On the other hand, the EM component in the Macau basalts cannot be linked to the same enriched lithospheric mantle identified with the tholeiites. However, their origin, though not very clear, is attributed to potassic metasomatism probably linked to the impact of the Fernando de Noronha plume on the continent. The similarities in isotopic signatures between the oceanic and continental basalts suggest a genetic link between both. Lastly, the Os isotopic compositions and TRD model ages contrained from the peridotite xenoliths in the Cenozoic basalts, record the occurrence of multiple magma extraction (1.3 to 0.1 Ga) and metasomatism events, confirming a complex chemical evolution in the subcontinental lithosphere in the far northeast of the Borborema Province.

La topographie de l’Afrique du Nord est marquée en domaine intraplaque par des bombements topographiques importants, associés à du magmatisme cénozoïque. Le Bouclier Touareg, un de ces bombements, est constitué d’un socle précambrien structuré à l’orogénèse panafricaine et culminant à plus de 2400 m d’altitude. Les séries paléozoïques affleurent actuellement sous forme de cuestas autour de ce bombement topographique. Localement, des témoins sédimentaires d’âge présumé crétacé, en discordance sur le socle précambrien, traduisent l’affleurement de celui-ci au Mésozoïque. Le volcanisme cénozoïque, qui se met également en place sur le socle, est actif entre 35 Ma et aujourd’hui. Afin de mieux contraindre l’évolution du Bouclier Touareg durant le Phanérozoïque, nous avons mené deux études : des travaux de modélisation géophysique, et une étude de thermochronologie basse température. L’étude géophysique a consisté en la modélisation de quatre profils longue distance permettant d’imager la structure lithosphérique. Nous avons montré que le bombement du Hoggar est actuellement soutenu par un important amincissement lithosphérique. En outre, nous avons estimé que sans cet amincissement, la topographie serait négative : le bassin ainsi reconstitué avant amincissement de la lithosphère aurait permis le dépôt d’une couverture sédimentaire d’épaisseur plurikilométrique. L’étude de thermochronologie basse température s’est portée sur deux méthodes : les analyses de traces de fission sur apatite, et les analyses (U-Th)/He sur apatite. Les analyses (U-Th)/He ont montré que le socle du Bouclier Touareg, avant d’avoir subi une importante exhumation à l’Eocène Supérieur, étant enseveli sous une couverture sédimentaire et chauffé à approximativement ~80°C. Les analyses de traces de fission ont permis de préciser que cette phase de chauffe, probablement sous couverture sédimentaire, du Bouclier Touareg a eu lieu entre 100 et 50 Ma. Ainsi, le bombement du Hoggar constituait probablement un bassin sédimentaire de grande dimension au cours du Crétacé supérieur/Paléocène. Ces résultats nous ont permis de discuter des mécanismes géodynamiques possiblement actifs durant le Cénozoïque. Nous proposons que le bombement actuel du Bouclier Touareg, ainsi que son magmatisme, soient liés à des perturbations thermiques des parties superficielles de l’asthénosphère. Ces perturbations seraient induites par d’importantes variations d’épaisseur de la lithosphère saharienne, et pourraient expliquer la présence d’autres bombements en Afrique du Nord. / The North-African intraplate topography is underlined by massive topographic swells associated with Cenozoic volcanism. The Tuareg Shield, which is one of these swells, consists of Precambrian basement which has been structured by the Pan-African orogeny and reaches currently an altitude of 2400 m. The Paleozoic sedimentary series are outcropping as important cuestas surrounding the topographic swell. Locally, some Mesozoic sedimentary remnants, lying unconformably over the basement, testify of its exposure during the Mesozoic. The Cenozoic volcanism, which is also taking place on the basement, shows ages from 35 Ma to Quaternary. In order to improve the knowledge of the Phanerozoic evolution of the Tuareg Shield, we performed two separated studies: geophysical modelling works, and a low temperature thermochronology study. The geophysical study consisted of the modelling of four long-distance profiles allowing imaging the lithospheric structure. We have shown that the Tuareg Shield swell is currently sustained by a strong lithospheric thinning. Moreover, we have estimated that without this thinning, the topography would be negative and that such basin, prior to thinning, would have allowed the deposition of a plurikilometric sedimentary cover. The low temperature thermochronological study has focused on two methods: apatite fission-track analysis, and apatite (U-Th)/He analysis. The latter shown that the Tuareg Shield, before an important Late Eocene exhumation, was buried under a sedimentary cover and heated at ~80°C. The fission-track analyses have shown that this heating stage of the Tuareg Shield, related to burying, occurred from 100 and 50 Ma. Thus, the Tuareg Shield was probably a wide scale sedimentary basin during the Upper Cretaceous – Paleocene. These results allowed us to discuss the geodynamic mechanisms potentially active during the Cenozoic. We proposed that the current doming of the Tuareg Shield, as well as its volcanism, were related to thermal perturbations of the shallower levels of the asthenosphere. These instabilities would have been generated by strong Saharan lithospheric thickness variations, and could explain the presence of others swells in North Africa.

The central and eastern United States is subject to seismic hazards from both natural and induced earthquakes, as evidenced by the 1811-1812 New Madrid earthquake sequence, consisting of at least three magnitude 7 and greater earthquakes, and by four magnitude 5 and greater induced earthquakes in Oklahoma since 2011. To mitigate seismic hazards, both earthquake sources and their effects need to be characterized. Ground motion site response can cause additional damage to susceptible infrastructure and buildings. Recent studies indicate that Vs30, one of the primary site-response predictors used in current engineering practice, is not reliable. To investigate site response in the New Madrid Seismic Zone, ratios of surface-to-bedrock amplitude spectra, TFT, from S-wave recordings at the two deep vertical seismic arrays in the sediment-filled upper Mississippi Embayment (i.e., VSAP and CUSSO) were calculated. The mean TFT curves were compared with theoretical transfer functions; the results were comparable, indicating that TFT estimates of the empirical, linear SH-wave site responses at these sites. The suitability of surface S-wave horizontal-to-vertical spectral ratios, H/V, for estimating the empirical site transfer function was also evaluated. The results indicate that mean S-wave H/V curves are similar to TFT at low frequencies (less than the fifth natural frequencies) at both CUSSO and VSAP. SH-wave fundamental frequency, f0, and fundamental-mode amplification, A0, were evaluated as alternatives to the Vs30 proxy to estimate primary linear site-response characteristics at VSAP, CUSSO, and nine other seismic stations in the CEUS. In addition, calculated f0 and A0 were compared with the first peaks of S-wave H/V spectral ratios. The f0 and A0 were found to approximate the 1-D linear, viscoelastic, fundamental-mode responses at most stations. Also, S-wave H/V from weak-motion earthquakes can be used to measure f0. However, S-wave H/V does not reliably estimate A0 in the project area. S-wave H/V observations reveal site response within the frequency band of engineering interest from deeper, unmodeled geological structures. Because damaging or felt earthquakes induced by hydraulic fracturing and wastewater disposal have occurred in the CEUS, characterizing background seismicity prior to new large-scale subsurface fluid injection is important to identify cases of and the potential for induced seismicity. The Rogersville Shale in the Rome Trough of eastern Kentucky is being tested for unconventional oil and gas potential; production of this shale requires hydraulic fracturing, which has been linked to induced seismicity elsewhere in the CEUS. To characterize natural seismicity and to monitor induced seismicity during testing, a temporary seismic network was deployed in the Rome Trough near the locations of new, Rogersville Shale oil and gas test wells. Using the real-time recordings of this network and those of other regional seismic stations, three years of local seismicity were cataloged. Only three earthquakes occurred in the Rome Trough of eastern Kentucky, none of which was associated with the deep Rogersville Shale test wells that were stimulated during the time the network was in operation.

Le Tien Shan est une chaîne de montagne active située à plus de 1000 km de la limite de plaque la plus proche, le front Himalayen. Elle possède une histoire ancienne qui va de la fin du Protérozoïque à la fin du Paléozoïque dans un contexte d’accrétions successives formant la plus grande chaîne d’accrétion du monde, la CAOB. Afin de comprendre comment l’histoire paléozoïque du Tien Shan influence la localisation de la déformation cénozoïque, nous avons dans un premier temps étudié la structuration de la chaîne pour en identifier les principales structures héritées. Nous avons mis en avant le partitionnement de la déformation entre les zones de sutures Sud et Nord au cours de la collision entre le Tarim et le Tien Shan au Carbonifère supérieur. Le front de collision est caractérisé par des chevauchements et des détachements au sein d’unités métamorphiques. Au Nord, se trouve une zone en décrochement caractérisée par une structure en fleur positive. Ensuite, ces résultats sont utilisés comme les conditions initiales de modèles numériques thermo-mécaniques 2D dont le but est de tester l’influence de ces zones héritées sur la localisation de la déformation cénozoïque. Ces modèles montrent que la déformation cénozoïque dans le Tien Shan se localise à la faveur de zones de faiblesses crustales et non mantelliques. De plus, nous avons pu établir que la bordure nord du Tarim avait une rhéologie proche de celle du Tien Shan. Finalement, à l’aide des modèles numériques une étude systématique a permis de mettre en évidence que le couplage entre l’érosion et le réseau de drainage jouait un rôle important dans la répartition et l’âge des roches de basse température exhumées. / The Tien Shan is an active mountain belt located at more than thousand kilometres of the closest plate boundary, the Himalayan front. Its Late Proterozoic to Late Paleozoic history takes place during the CAOB accretion which represents the largest accretionary belt in the world. In order to understand how the Paleozoic tectonics of the Tien Shan influences the Cenozoic strain localization, we aim at identifying the main inherited structures of the belt. We highlighted the strain partitioning between the North and South suture zones during the Tarim-Tien Shan Late Carboniferous collision. The collisional front is characterized by thrusts and detachments in metamorphic units while northward, a strike-slip zone is evidenced by a positive flower structure. Then, these results are used as variable inputs in 2D numerical thermo-mechanical models in order to assess the role of these inherited structures on the Cenozoic strain localization. These models show that the Cenozoic deformation in the Tien Shan is localized in favour of crustal weak zones instead of mantellic ones. Moreover, we are able to show that the northern border of the Tarim has a Tien Shan like rheology. Finally, we performed a systematic numerical modelling analyse in order to show that the coupling between erosion and drainage network plays an important role on low temperature rocks exhumation ages and repartition.