Induced seismicity is a common phenomenon that occurs as soon as the stress state in the subsurface is externally altered in a way that faults are destabilized. It is especially problematic in stable tectonic regions where the area is not used to earthquakes; the infrastructure is not built to withstand ground movement and thus when the induced seismicity occurs damage can follow. In this thesis, mining-induced seismicity has been studied at the Dannemora mine, located in central Sweden, with the aim to locate the seismicity and gain understanding of its occurrence and behavior. The mining company, Dannemora Mineral AB, provided with blasting locations and times, as well as maps over the mine's orebodies and stopes. Seismic data acquired between 01 July 2014 - 25 March 2015 from 4 temporary seismic stations, deployed in the summer of 2014 surrounding the mine, along with 8 SNSN stations was analyzed. The project encompassed field work and processing of the data, which involved different methods to investigate the characteristics of the mine's seismicity: Statistics were kept to record the activity rate of the seismicity over time; spectral analysis was used to study the frequency content of the seismicity; particle motion plots were constructed to identify body-phases in the seismicity; Local Earthquake Tomography was used to upgrade the velocity model of the mine and to relocate the induced seismicity with more accuracy; cross-correlation was used to find events originating from similar sources; and finally, magnitude analysis was used to compare the different types of seismicity within the mine. Three main types of induced events were observed in the mine: low-frequency events with clear first arrivals, emergent events with long duration, and high-frequency events that could either have clear first arrivals or emergent-like with long durations. Through the analysis of their characteristics, they were linked to different types of rockbursts. The low-frequency events were linked to both reactivation of fault zones triggered by the mine activity, and rockbursts within the mine directly related to the mining. The emergent and high-frequency events were also linked to rockbursts directly related to the mine activity, e.g. ejection of rock from the tunnel walls or arch collapses in stopes.

Thesis (Habilitationsschrift)--Ruhr-Universität Bochum, 2005. / "February 2006"--P. [2] of cover. Includes bibliographical references. Also available via the World Wide Web.

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

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.

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.

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.

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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