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Mechanical Modeling of Natural and Anthropogenic Fluid-Rock Interactions: Volcano Deformation and Induced SeismicityJanuary 2018 (has links)
abstract: The dynamic Earth involves feedbacks between the solid crust and both natural and anthropogenic fluid flows. Fluid-rock interactions drive many Earth phenomena, including volcanic unrest, seismic activities, and hydrological responses. Mitigating the hazards associated with these activities requires fundamental understanding of the underlying physical processes. Therefore, geophysical monitoring in combination with modeling provides valuable tools, suitable for hazard mitigation and risk management efforts. Magmatic activities and induced seismicity linked to fluid injection are two natural and anthropogenic processes discussed in this dissertation.
Successful forecasting of the timing, style, and intensity of a volcanic eruption is made possible by improved understanding of the volcano life cycle as well as building quantitative models incorporating the processes that govern rock melting, melt ascending, magma storage, eruption initiation, and interaction between magma and surrounding host rocks at different spatial extent and time scale. One key part of such models is the shallow magma chamber, which is generally directly linked to volcano’s eruptive behaviors. However, its actual shape, size, and temporal evolution are often not entirely known. To address this issue, I use space-based geodetic data with high spatiotemporal resolution to measure surface deformation at Kilauea volcano. The obtained maps of InSAR (Interferometric Synthetic Aperture Radar) deformation time series are exploited with two novel modeling schemes to investigate Kilauea’s shallow magmatic system. Both models can explain the same observation, leading to a new compartment model of magma chamber. Such models significantly advance the understanding of the physical processes associated with Kilauea’s summit plumbing system with potential applications for volcanoes around the world.
The unprecedented increase in the number of earthquakes in the Central and Eastern United States since 2008 is attributed to massive deep subsurface injection of saltwater. The elevated chance of moderate-large damaging earthquakes stemming from increased seismicity rate causes broad societal concerns among industry, regulators, and the public. Thus, quantifying the time-dependent seismic hazard associated with the fluid injection is of great importance. To this end, I investigate the large-scale seismic, hydrogeologic, and injection data in northern Texas for period of 2007-2015 and in northern-central Oklahoma for period of 1995-2017. An effective induced earthquake forecasting model is developed, considering a complex relationship between injection operations and consequent seismicity. I find that the timing and magnitude of regional induced earthquakes are fully controlled by the process of fluid diffusion in a poroelastic medium and thus can be successfully forecasted. The obtained time-dependent seismic hazard model is spatiotemporally heterogeneous and decreasing injection rates does not immediately reduce the probability of an earthquake. The presented framework can be used for operational induced earthquake forecasting. Information about the associated fundamental processes, inducing conditions, and probabilistic seismic hazards has broad benefits to the society. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018
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Modeling the Proterozoic basement’s effective stress field, assessing fault reactivation potential related to increased fluid pressures in south central Kansas and north central Oklahoma, and improving seismic imaging of basement faulting within Wellington and Anson-Bates Fields, Sumner County, KansasKeast, Ryan Taylor January 1900 (has links)
Master of Science / Department of Geology / Brice LaCroix / Abdelmoneam Raef / South-central Kansas has experienced an increase in seismic activity within the Proterozoic basement over the past 10 years. In 2009, Oklahoma seismic stations recorded 50 earthquakes statewide, a 200% increase from 2008. Oklahoma Geological Survey (OGS) seismograph stations recorded 1,028 in 2010, an increase of over 2000% from 2009. Between 2000-2012, Kansas experienced only 12 earthquakes statewide. Beginning in September 2013, clusters of seismic events in south-central Kansas began to increase. In 2015 alone, Kansas seismograph stations recorded 448 earthquakes, of which 166 resulted in a magnitude 2.0 or greater. Since 2013, United States Geological Survey (USGS) seismograph stations have recorded over 12,000 earthquakes within Kansas and Oklahoma. Pore fluid pressure increases associated with recent high-rate wastewater injection into the dolomitic Arbuckle disposal zone are hypothesized as cause of reactivation of the faulted study region’s Proterozoic basement. Although the magnitude of fluid-pressure change required for reactivation of these faults is likely low given failure equilibrium conditions in the midcontinent, heterogeneities (i.e. permeability, porosity, fluid pressure) in the basement could allow for a range of fluid pressure changes associated with injection. This research aims to quantify the fluid pressure changes responsible for fault reactivation of the Proterozoic basement. To address this issue, we use 97 earthquake focal mechanisms and over 12,000 seismic events, from the USGS catalog, within an area encompassing ~ 4,000 km². Focal mechanism data was utilized to determine the regional stress field present within the study region. Nodal plane data extracted from the focal mechanisms was crucial to identifying lineaments within the underlying basement complex.
A 3D seismic dataset covering the Wellington and Anson Bates Fields in north central Sumner County, Kansas was utilized for enhanced structural delineation of an interpreted faultnetwork affecting the Mississippian and Arbuckle Groups, to investigate whether it impacts the underlying granitic basement and its complex network of potentially interconnected fault planes. Smoothed similarity and spectral whitening analyses were applied to the dataset to improve depth of investigation and uncover fault lineaments masked by seismic attenuation due to increasing depth. An interpreted network of fault planes at depths of 3.5 km was uncovered beneath Wellington Field. The lineaments are well aligned with known structural features present within the Proterozoic basement, the Central Kansas Uplift and the Nemaha Ridge-Humboldt fault zone.
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Méthodes télésismiques d'estimation de la profondeur des séismes : développements et applications / Study of the earthquake's depth effect on the weak and moderate earthquakes properties and on seismic movementsLetort, Jean 11 July 2014 (has links)
Cette thèse traite de l'étude de la profondeur des séismes modérés (4 < M < 5.5), à travers l'utilisation de données telesismiques, c'est à dire à partir d'enregistrements de sismographes situes a des distances de 3000 jusqu'à 9000 km de la source. L'estimation de la profondeur d'un séisme s'obtient en comparant les temps d'arrivée de l'onde directe (P) générée par ce séisme, avec ceux des ondes réfléchies sur la surface de la Terre, au-dessus du foyer du séisme (les phases de profondeur pP, sP). Nous utilisons le réseau du CTBTO (Comprehensive Test-Ban-Treaty-Organization, composé de mini-réseaux (10-20 sismographes), nous permettant de développer deux nouvelles méthodes d'estimation de la profondeur. La première est une inversion complète du mécanisme au foyer, simultanément a la profondeur. La seconde est une méthode d'analyse spectrale : le cepstre. A l'aide d'exemples de séismes en zone intracontinentale, nous montrons que ces deux méthodes sont complémentaires et qu'elles apportent une information nouvelle sur l'estimation de la profondeur pour les séismes de régions peu instrumentées. Dans un second temps, une optimisation de la méthode cepstrale a permis d'étendre l'estimation de la profondeur a l'utilisation de stations isolées provenant du réseau mondial IRIS. Cette nouvelle méthode, complètement automatique, a permis de localiser en profondeur les séismes de magnitude supérieure à 4.5 pour la zone de subduction de Guerrero (Mexique). Nous avons ainsi mis en évidence une répartition homogène des profondeurs des séismes dans la zone du gap de Guerrero. En combinant ces estimations de la profondeur de l'interface avec celles obtenues a l'aide d'une relocalisation de l'ensemble de la sismicité (par la méthode de l'ISC-Locator), nous proposons une imagerie de la géométrie de la subduction. Nous avons ensuite étudié l'influence de la profondeur sur les propriétés sismiques des séismes. En particulier, nous avons évalué la relation entre la profondeur et la chute de contrainte pour les séismes récents et modérés de la plaine du Pô, en Italie. Pour cela, nous nous sommes appuyés sur le réseau accéléromètrique régional de l'INGV Milan pour estimer les spectres sources de ces séismes, puis en déduire les fréquences coins et les chutes de contraintes associées. Ces spectres sources s'obtiennent à l'aide d'une méthode d'inversion qui sépare simultanément l'effet de l'atténuation, les effets de sites et l'effet de la source sur les spectres des ondes S, générées par les séismes et enregistrées en surface par les accéléromètres. Après inversion, nous trouvons une faible augmentation de la chute de contrainte avec la profondeur. / This thesis deals with depth estimations of moderate earthquakes (4 < M < 5.5), observed through the use of teleseismic data. At teleseismic distances (from 3000 to 9000 km), estimations of earthquake depths come from the estimation of the delays between the arrival time of the direct P-wave and the arrival times of the waves which have been reflected on the surface above the source (known as : depth phases pP and sP). The CTBTO (Comprehensive Test-Ban- Treaty-Organization) monitoring system allows the detection of these teleseismic phases for weak events, with magnitudes below 5, since this global network is composed by arrays (10-20 close single stations, in the same location). Using this network, two methods were developed for teleseismic depth estimation. First, a depth-phase recognition method is applied, based on a new improved cepstral analysis. In addition, we have developed a focal mechanism genetic algorithm inversion. We have applied these two methods for earthquakes occurring in intracontinental areas and we have proved that these new depth determinations provide new and complementary information about the source for barely instrumented areas. We have also developed another method, completely blind and automatic, which consists in an improvement of the cepstral analysis. The reliability of this method to improve depth estimation has been proved by relocating the recent moderate seismicity of the Guerrero subduction area (Mexico). In the Guerrero area, this cepstral analysis efficiently clusters event locations. We then use teleseismic waves reflected on the subduction interface to evaluate the depth of the interface above the focal hypocenter, which allows to specify the subduction interface geometry. We have finally conducted an exhaustive analysis of the depth distributions, based on a relocalization of the ISC catalogue using the new ISC-Locator algorithm and we provide an improved image of the subduction. Finally, we have conducted a study of the relationship between earthquake depths and seismic properties. In particular, we have focused on the burning issue about the links between stress drops and focal depths. We have found an interesting case study with the Po Plain recent seismicity (Northern Italy). Brune's stress drops and magnitudes have been estimated from a generalized parametric inversion using the regional accelerometric network from INGV Milano. We have shown that there is only a slight dependency between stress drops and earthquake depths in the Po Plain.
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Etude comparative de la sédimentation co-sismique sur deux sites tectoniques actifs : la mer de Marmara et le golfe de Corinthe : développements méthodologiques, apports à l'estimation de l'aléa sismique régional / Comparative study of co-seismic sedimentation in two tectonically active areas : the sea of Marmara and the gulf of Corinth : methodological developments, implication for seismic hazards assessmentCampos Serrano, Corina 23 June 2014 (has links)
La partie orientale de la Méditerranée, est une des régions sismiques les plus actives en Europe. La présence dans cette région de nombreux lacs et bassins marins isolé fait de cette région un endroit idéal pour étudier l'enregistrement de l'activité sismo- tectonique et les principaux changements climatiques dans des environnements subaquatiques. Dans cette thèse, nous nous intéressons à l'étude de l'enregistrement paléosismique subaquatique du Quaternaire tardive dans deux bassins: la Mer de Marmara et le Golfe de Corinthe. Ces derniers sont des bassins marins isolés traversés par des failles majeures (par exemple, la faille Nord Anatolienne). Nous nous sommes concentrés sur l'identification des traces laissées par des paléoséismes dans l'enregistrement sédimentaire, en particulier, les couches nommées ici: "homogenites + turbidites" (HmTu), lequel représentent des événements sédimentaires quasi instantanés induits par des secousses sismiques. Leur identification a été réalisée à partir des analyses sédimentologiques classiques et des propriétés magnétiques, en particulier, l'anisotropie de la susceptibilité magnétique. Les analyses ont été effectuées sur les sédiments carottés à l'aide du système géant à piston CALYPSO. Ces sédiments représentent les dernières 17 cal ka BP de sédimentation, et ont enregistré le dernier passage de conditions non marine à des conditions marines. Dans la mer de Marmara, ce passage a été identifié autour de 12,8 cal ka BP, tandis que, dans le golfe de Corinthe était d'environ 11,7 cal ka BP. Dans les deux bassins, l'enregistrement des événements instantanés considérés comme induits par des séismes a permis l'estimation d'un intervalle moyen de récurrence. Dans le bassin de Çınarcık de la mer de Marmara, l'intervalle de récurrence moyenne minimale varie entre ~155 et ~365 ans, tandis que pour la partie orientale du golfe de Corinthe, l'intervalle de récurrence moyenne minimale varie entre ~400 et ~500 ans. Enfin, dans le bassin central de la mer de Marmara, l'étude des événements HmTu corrélées sur les côtés opposés d'un segment de la faille nord-anatolienne permet d'estimer le décalage vertical co-sismique pour une période continue de 2 ka. Des valeurs significatives observées étaient des décalées verticalement (jusqu'à 144 cm), ce qui implique un déplacement verticalement dominant (normal) pour ce segment. / The Eastern Mediterranean is one of most seismically active and rapidly deforming regions in Europe. The presence in this region of numerous lakes and isolate marine basins makes this region an ideal area to study the record of the seismo-tectonic activity and the main climatic changes in sub-aquatic environments. In this thesis we are interested in studying the Late Quaternary sub-aquatic paleoseismic record of two basins: The Sea of Marmara and The Gulf of Corinth. Both are isolated deep marine basins, crossed by major faults (e.g. the North Anatolian Fault). We focused on identifying the traces left by paleoearthquakes in the sedimentary record, particularly, the layers named here: “homogenites+turbidites” (HmTu), which represent individual sedimentary seism-induced events. Their identification was performed through classical sedimentological analyzes and magnetic properties, in particular the Anisotropy of Magnetic Susceptibility. Analyzes were conducted on sediment recovered by long Calypso piston cores. These sediments represent the last 17 cal kyr BP of sedimentation, and have recorded the last non-marine to marine change. In the Sea of Marmara, this passage was identified around 12.8 cal kyr BP, whereas in the Gulf of Corinth was around 11.7 cal kyr BP. In both basins, the record of the earthquake induced instantaneous events allowed the estimation of the average earthquake recurrence interval. In the Çinarcik Basin of the Sea of Marmara, the minimum average recurrence interval varies between ∼155 and 365 yr, while for the eastern part of the Gulf of Corinth the minimum average recurrence interval varies between ∼400 and ∼500 yr. Finally, in the Central Basin of the Sea of Marmara, the study of correlated HmTu events at opposite sides of a segment of the North Anatolian Fault allows the estimation of the co-seismic vertical offset for a continuous period of 2 kyr. Significant values of vertical offset were observed (up to 144 cm), implying a dominant vertical (normal) throw for this fault segment.
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Estudo integrado da camada de basalto em Bebedouro - SP, Bacia do Paraná: relocalização dos sismos induzidos por poços tubulares / Integrated Study of the basalt layer in Bebedouro SP, Paraná Basin: Relocation of earthquakes induced by wells.Gabriel Enrique Dicelis Salamanca 03 August 2011 (has links)
Dicelis, G. E., Estudo Integrado da Camada de Basalto em Bebedouro SP, Bacia do Paraná: Relocalização dos sismos induzidos por poços tubulares, 2011. Dissertação de Mestrado Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, SP. A partir de 2004, a população do distrito de Andes, Bebedouro (SP), passou a sentir pequenos tremores de terra. Uma rede sismográfica instalada em 2005 mostrou que os sismos locais são induzidos por poços tubulares profundos usados para irrigação de lavouras (Assumpção et al., 2007). Neste projeto de pesquisa foi melhorada a localização desses sismos, usando análise da forma de onda e os tempos de chegada das ondas P e S, com o propósito de efetuar uma melhor análise da sismicidade induzida. Para isto foram aproveitados resultados de estudos anteriores como sísmica de refração, dispersão de ondas de superfície, sondagem elétrica vertical, função do receptor e TDEM. Para obter o melhor modelo de velocidades 1D, foram testados diferentes algoritmos de localização e técnicas de relocalização de hipocentros, para aproximadamente 3000 microtremores gravados pela rede sismográfica no período 2005 2010. Os resultados mostraram que as profundidades focais dos sismos relocalizados ficaram em sua maioria dentro da camada de basalto, a menos de 500m de profundidade. Este resultado confirma que os sismos estão relacionados com a perturbação do equilíbrio de tensões (pressões) geológicas, em zonas de fraturas já existentes dentro da camada de basalto. Foi usada uma combinação de correlação cruzada e tempos de chegada para analisar um conjunto de sismos, baseada na similaridade dos seus sismogramas. Foi melhorada a distribuição hipocentral o que permitiu determinar claramente uma solução do plano focal de um cluster, o que indicou a existência de uma falha normal de orientação WNW-ESSE e mergulho para o norte, com extensão NNE-SSW (eixo-T). Este mecanismo pode complementar os dados de esforços na região sudeste. / Dicelis, G. E., Integrated Study of the basalt layer in Bebedouro SP, Paraná Basin: Relocation of earthquakes induced by wells, 2011. Master dissertation - Institute of Astronomy, Geophysics and Atmospheric Sciences of the University of Sao Paulo, Brazil. Since 2004 the population of the district of Andes, Bebedouro SP, began to feel small earthquakes. A seismograph network installed in 2005 showed that earthquakes are caused by local deep wells used for irrigation of crops (Assumpção et al., 2007). In this research project we improved the location of these earthquakes, using analysis of waveform and the arrival times of P and S waves, in order to make a better analysis of the induced seismicity. To better relocate the events we determined a velocit model using results of previous studies such as seismic refraction, surface wave dispersion, vertical electrical sounding, receiver function and TDEM. The best fit 1D model was achieved testing different localization algorithms and techniques for relocation of hypocenters for approximately 3000 microtremors recorded by seismograph network to the period 2005 2010. The results showed that the focal depths of the relocated earthquakes are mostly within the basalt layer, less than 500m depth. This confirms that the earthquakes are related with disturbance of geological stresses (pressures) in pre-existing fracture zones within the basalt layer. We used a combination of cross-correlation and arrival times for analyze a set of earthquakes, based on the similarity of their recorded seismograms. The hypocentral distribution was improved allowing a clear determination of the best fit fault plane solution for one cluster, which indicates the existence of a normal fault with direction WNW-ESE and dip to the north, with NNE-SSW extension (T-axis). This mechanism may complement the stress data in the Southeast Brazil.
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Sustainable Development in China’s Decision Making on Large Dams: A case study of the Nu River BasinChen, Huiyi January 2013 (has links)
China’s consumption of electricity is increasing with its economic development. Although the main supply of electricity power is still coal, the government has recognized the importance of renewable energy and energy transition. China officially made a pledge of carbon emission reduction after the Copenhagen conference and enhanced its efforts to promote the environmentally sustainable alternatives to coal-fired power plants. Hydropower is the central of this strategy to achieve sustainable energy production. Due to the ecological and social influences, the 13 dams concentrated on the Nu River have caused a fierce debate over the past decade. Premier Wen even halted twice the project in 2004 and 2009. However, faced with increasing energy demand and Copenhagen commitment for carbon emission reduction, hydropower development remains a top priority and the 12th Five-Year plan will continue the construction of the Songta Dam on the Nu River. The other four dams including Maji, Yabiluo, Liuku and Saige should undergo orderly preparation as well. Thus this thesis aims to evaluate to what extent has China’s decision to build large dams on Nu River taken sustainable development into serious consideration under the seven priority strategies policy framework of World Commission on Dams. The study finds out that China’s decision to build dams considered the environmental and social issues, but when it comes to population and displacement issues, more efforts of implementation are needed and the process of benefits sharing and getting acceptance as well.
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INITIAL MICROSEISMIC RECORDINGS AT THE ONSET OF UNCONVENTIONAL HYDROCARBON DEVELOPMENT IN THE ROME TROUGH, EASTERN KENTUCKYHolcomb, Andrew 01 January 2017 (has links)
The Cambrian Rogersville Shale is a part of a hydrocarbon system in the Rome Trough of eastern Kentucky and West Virginia that can only be produced unconventionally. In Kentucky, the Rogersville Shale ranges in depth from ~1,800 to ~3,700 m below the surface with the crystalline basement ~1,000 m lower than the formation’s base. Baseline Rome Trough microseismicity data were collected, focusing on wastewater injection wells and recently completed and planned unconventional hydrocarbon test wells in the Rogersville Shale, using thirteen broadband seismic stations installed between June, 2015 and June, 2016 and existing University of Kentucky and central and eastern United States network stations. In addition, the network’s minimum detection threshold, the magnitude at which the theoretical signal exceeds the noise by a factor of 3 between 1 and 20 Hz for at least 4 stations, was estimated for the project area. Thirty-eight local and regional events were located and magnitudes were calculated for each event. No events were proximal to operating disposal or hydrocarbon test wells, nor did any occur in the eastern Kentucky’s Rome Trough. The minimum detection threshold varies between 0.4 and 0.7 Mw from 0000-1100 UTC and 0.6 to 0.9 Mw from 1100-2300 UTC.
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Vulnérabilité et perception face aux tremblements de terre en France, 1650-1850 / Vulnerability and perception to earthquake in France, 1650-1850Fradet, Thibault 14 December 2016 (has links)
Cette thèse d’histoire vise in fine l’amélioration des méthodologies de détermination de l’aléa qui reposent sur les données macrosismiques dans le cas des séismes historiques. A cette fin, l’effort de recherche fondamentale, de même que l’analyse de la vulnérabilité des sociétés du passé face aux aléas naturels passent par la création et l’utilisation d’outils méthodologiques applicables aux séismes historiques (critique historique, lexique, cartographie). La thèse se compose de deux parties à la fois distinctes et indissociables : d’une part la vulnérabilité des populations anciennes aux tremblements de terre, d’autre part celle du bâti ancien. Mêler la mise en contexte des documents disponibles à une recherche archivistique robuste et fine permet d’intégrer le comportement des communautés touchées.Les bornes chronologiques choisies correspondent au développement de la presse et la naissance de la science moderne d’une part, l’entrée dans l’ère de la Révolution industrielle d’autre part. Ce choix est également motivé par la disponibilité restreinte et l’analyse plus complexe des documents pour la période qui précède le XVII e siècle et la naissance de la sismologie pour la seconde partie du XIX e siècle.Trois cas d’études (Bagnères-de-Bigorre, 1660 ; Manosque, 1708 ; Entre-Deux-Mers, 1759) permettent d’explorer bon nombres de pistes de recherches menant à une appréhension, analyse et interprétation desdocuments historiques par l’utilisation d’outils créés spécialement dans ce but. / This thesis of history is ultimately the improvement of the methodologies of hazard based on macroseismic data in the case ofhistorical earthquakes. To this end, the effort of basic research, as well as the analysis of the vulnerability of societies of the past to natural hazards involves the creation and the use of methodological tools applicable to historical earthquakes (historical criticism, lexicon, and mapping). The thesis consists into two parts at once distinct and indivisible: firstly the old vulnerability to earthquakes, secondly the vulnerability of ancient buildings.Mixing the context of the available documents with a robust and thin archival research allows integrating the behavior of affected ommunities.Selected time-series terminals correspond to the development of the press and the birth of modern science a hand, entering the era of the Industrial Revolution on the other. This choice is also motivated by the limited availability and more complex analysis of the documents for the period preceding the 17th century and the birth of Seismology for the second part of the 19th century.Three case studies (Bigorre, 1660; Manosque, 1708; Entre-Deux-Mers, 1759) allow exploring many leads of research leading to a better apprehension, analysis and interpretation of historical documents by theuse of tools specifically created for this purpose.
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Geodynamická mapa Moravy a okolí / Geodynamical Map of Moravian and surrounding.Rajnoha, Milan January 2013 (has links)
Result of this graduation theses is Geodynamic map of Moravia in scale 1:500 000. There were used available data from GPS measurements, seismic, geomorphologic and other data to construct map. Map is worked in GIS software. On the backround of researched data, there are determinated some locations, which are characterized by recent tectonic activity. These are analyzed for more detail.
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Injections de fluide dans une zone de faille (LSBB, Rustrel) : sismicité induite et déformation asismique / Fluid-injections in a fault zone (LSBB, Rustrel) : induced seismicity and aseismic deformationDuboeuf, Laure 02 February 2018 (has links)
Mieux appréhender la relation entre fluides, sismicité et déformation asismique est crucial en terme de risques et de ressources. Dans les zones d'injections de fluide une augmentation du taux de sismicité est observée, certains événements dépassant Mw=5. Quel est alors le rôle des fluides dans le déclenchement et le contrôle de la sismicité ? Une série d'injections de fluide à haute-pression a été réalisée dans les séries carbonatées du LSBB (Rustrel), dans la zone endommagée d'une faille inactive à 280 m de profondeur. Ces expériences in-situ ont permis l'étude des réponses sismiques et hydromécaniques (enregistrées par un large réseau de capteurs) de différentes structures géologiques à une stimulation hydraulique. Seuls certains tests ont été impactés par des séismes bien qu'une rupture ait été mesurée au point d'injection par un extensomètre. 215 séismes ont été détectés et se caractérisent par un contenu haute-fréquence (0.6 à 3 kHz) et de faible magnitude (-4.1 à -3.1). Leur localisation absolue et relative (précision de 1.5 m) a mis en évidence un manque de séismes à proximité du puits d'injection. En comparant le moment sismique cumulé et un moment équivalent de déformation, plus de 96 % de la déformation est asismique. Deux comportements sismiques distincts ont montré qu'au moins une partie de la sismicité était contrôlée par un transfert de contraintes. L'interprétation jointe des données géologiques, mécaniques, hydrogéologiques et sismiques a permis de reconstruire le mouvement des blocs de roches au point d'injection. Ainsi, la stimulation hydraulique de faille génèrerait un mouvement asismique, qui par transfert de contrainte, déclencherait la sismicité. / Better understanding how fluids pressure produce seismic or aseismic motion along faults is an important goal for seismic hazard assessment and for geological reservoir monitoring. Seismicity rate increase in fluid injection areas where some events may reach magnitude greater than 5. How fluids may induce and control seismicity? High-pressure fluid injections were performed in limestones, in the damaged zone of an inactive fault at 280m depth. These in-situ experiments allow to study the seismological and hydromechanical responses (recorded by 31 sensors) of different fracture types to a fluid perturbation. Only a few tests have generated seismicity even if ruptures are observed with a displacement sensor at the injection point. 215 earthquakes were detected and are characterized by high frequency content (0.6 to 3 KHz) and weak magnitude (-4.1 to -3.1). The relative and absolute locations (1.5m accuracy) indicate a lack of events in the vicinity of injection borehole. Comparing cumulated seismic moment with an equivalent deformation moment, more than 96% of the deformation is aseismic. Two distinct seismic behavior show that at least one part of the seismicity might be controlled by a stress transfer in the medium. Moreover, the joined interpretation geological, mechanical, hydrogeological and seismic data allow to build bloc motions at the injection point. Finally, our experiments showed that fluid injection mainly drives aseismic motion and the seismicity might be only an indirect effect related to stress transferred from the volume deformed by fluid pressurization.
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