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Ma, Xu, Erik Westman, Dave Counter, Farid Malek, and Brent Slaker. "Passive Seismic Imaging of Stress Evolution with Mining-Induced Seismicity at Hard-Rock Deep Mines." Rock Mechanics and Rock Engineering 53, no. 6 (2020): 2789–804. http://dx.doi.org/10.1007/s00603-020-02076-5.
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AbstractThis work aims to examine the stress redistribution with evolving seismicity rates using a passive seismic tomographic tool. We compiled a total of 26,000 events from two underground mines and partitioned them into multiple clusters in a temporal sequence, each of which contains 1000 events. To image stress redistribution associated with seismicity rates, we then run the tomographic studies using each cluster to yield seismic tomograms and computed the corresponding seismicity rate. We found that high velocity anomalies grew with the increase of seismicity rates, and they switched to a shrinking tendency under low seismicity rates. Results of this study imply that seismicity rates increase with increasing stress concentration and decrease with decreasing stress concentration. This study highlights the value of utilizing passive seismic tomography for estimating stress evolution associated with the change of seismicity rates at underground mines. Our findings illuminate the applications of using mining-induced seismicity to assess stress redistribution associated with seismicity rates at hard-rock mines, providing insights into seismic hazards for deep mining.
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Aochi, Hideo, Julie Maury, and Thomas Le Guenan. "How Do Statistical Parameters of Induced Seismicity Correlate with Fluid Injection? Case of Oklahoma." Seismological Research Letters 92, no. 4 (2021): 2573–90. http://dx.doi.org/10.1785/0220200386.
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Abstract The seismicity evolution in Oklahoma between 2010 and 2018 is analyzed systematically using an epidemic-type aftershock sequence model. To retrieve the nonstationary seismicity component, we systematically use a moving window of 200 events, each within a radius of 20 km at grid points spaced every 0.2°. Fifty-three areas in total are selected for our analysis. The evolution of the background seismicity rate μ is successfully retrieved toward its peak at the end of 2014 and during 2015, whereas the triggering parameter K is stable, slightly decreasing when the seismicity is activated. Consequently, the ratio of μ to the observed seismicity rate is not stationary. The acceleration of μ can be fit with an exponential equation relating μ to the normalized injected volume. After the peak, the attenuation phase can be fit with an exponential equation with time since peak as the independent variable. As a result, the evolution of induced seismicity can be followed statistically after it begins. The turning points, such as activation of the seismicity and timing of the peak, are difficult to identify solely from this statistical analysis and require a subsequent mechanical interpretation.
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Badawy, A., S. M. Abdel-Monem, K. Sakr, and Sh M. Ali. "Seismicity and kinematic evolution of middle Egypt." Journal of Geodynamics 42, no. 1-3 (2006): 28–37. http://dx.doi.org/10.1016/j.jog.2006.04.003.
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Nasir, Asma, Esther Hintersberger, and Kurt Decker. "The temporal evolution of seismicity and variability of b-values along the Vienna Basin Transfer Fault System." Austrian Journal of Earth Sciences 116, no. 1 (2023): 1–15. http://dx.doi.org/10.17738/ajes.2023.0001.
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Abstract The Vienna Basin Transfer Fault System (VBTFS) is the most active fault system in the region between the Eastern Alps, the western Carpathians and the Pannonian Basin. The spatial and temporal distribution of earthquakes along the fault system shows a heterogeneous pattern including a long-time decay of seismicity at the northern part of the VBTFS, which was interpreted to result from a long aftershock sequence subsequent to the 1906 Dobrá Voda earthquake (M=5.7). In this paper we investigate if other segments of the VBTFS display similar long-term declines of seismicity that might indicate long aftershock sequences following strong, yet unrecorded, earthquakes in historical times. In order to analyse the distribution of seismicity, the VBTFS is divided into arbitrary segments of about 50 km length each. The segments are chosen to overlap each other to avoid missing information from neighbouring segments due to arbitrarily selected segment boundaries. For each segment we analyse the temporal evolution of seismicity and calculate the parameters of the corresponding Gutenberg-Richter (GR) relation. The temporal seismicity patterns revealed from the segments covering the Dobrá Voda area confirm the protracted aftershock sequence following the 1906 earthquake. All but one of the other segments do not show temporal changes of seismicity comparable to the long-term Dobrá Voda aftershock sequence. Seismicity patterns, however, include short-term Omori-type aftershocks following moderate earthquakes such as the 2000 Ebreichsdorf earthquake (M=4.8). The segment covering the SW tip of the VBTFS revealed a 200 years long gradual decrease of the largest observed magnitudes starting with the 1794 Leoben (M=4.7) earthquake. The 1794 event is the oldest earthquake listed in the catalogue for the region under consideration. It therefore remains open if the recorded decay of seismicity results from the 1794 event, or a stronger earthquake before that time. The latter is corroborated by the low magnitude of the 1794 earthquake which would typically not be considered to cause long aftershock sequences. GR a- and b-values, calculated for the individual segments, vary significantly along the VBTFS. Values range from 0.47 to 0.86 (b-values) and 0.81 to 2.54 (a-values), respectively. Data show a significant positive correlation of a- and b-values and a coincidence of the lowest b-values with fault segments with large seismic slip deficits and very low seismicity in the last approximately 300 years. These parts of the VBTFS were previously interpreted as “locked” fault segments, which have a significant potential to release future strong earthquakes, in spite of the fact that historical and instrumentally recorded seismicity is very low. We find this interpretation corroborated by the low b-values that suggest high differential stresses for these fault segments.
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Vallianatos, Filippos, Georgios Michas, and George Hloupis. "Seismicity Patterns Prior to the Thessaly (Mw6.3) Strong Earthquake on 3 March 2021 in Terms of Multiresolution Wavelets and Natural Time Analysis." Geosciences 11, no. 9 (2021): 379. http://dx.doi.org/10.3390/geosciences11090379.
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On 3 March 2021, a strong, shallow earthquake of moment magnitude, Mw6.3, occurred in northern Thessaly (Central Greece). To investigate possible complex correlations in the evolution of seismicity in the broader area of Central Greece before the Mw6.3 event, we apply the methods of multiresolution wavelet analysis (MRWA) and natural time (NT) analysis. The description of seismicity evolution by critical parameters defined by NT analysis, integrated with the results of MRWA as the initiation point for the NT analysis, forms a new framework that may possibly lead to new universal principles that describe the generation processes of strong earthquakes. In the present work, we investigate this new framework in the seismicity prior to the Mw6.3 Thessaly earthquake. Initially, we apply MRWA to the interevent time series of the successive regional earthquakes in order to investigate the approach of the regional seismicity at critical stages and to define the starting point of the natural time domain. Then, we apply the NT analysis, showing that the regional seismicity approached criticality a few days before the occurrence of the Mw6.3 earthquake, when the κ1 natural time parameter reached the critical value of κ1 = 0.070.
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Mignan, A. "Static behaviour of induced seismicity." Nonlinear Processes in Geophysics Discussions 2, no. 6 (2015): 1659–74. http://dx.doi.org/10.5194/npgd-2-1659-2015.
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Abstract. The standard paradigm to describe seismicity induced by fluid injection is to apply nonlinear diffusion dynamics in a poroelastic medium. I show that the spatiotemporal behaviour and rate evolution of induced seismicity can, instead, be expressed by geometric operations on a static stress field produced by volume change at depth. I obtain laws similar in form to the ones derived from poroelasticity while requiring a lower description length. Although fluid flow is known to occur in the ground, it is not pertinent to the behaviour of induced seismicity. The proposed model is equivalent to the static stress model for tectonic foreshocks generated by the Non-Critical Precursory Accelerating Seismicity Theory. This study hence verifies the explanatory power of this theory outside of its original scope.
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Denlinger, Roger P., and Daniel R. H. O’Connell. "Evolution of Faulting Induced by Deep Fluid Injection, Paradox Valley, Colorado." Bulletin of the Seismological Society of America 110, no. 5 (2020): 2308–27. http://dx.doi.org/10.1785/0120190328.
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ABSTRACT High-pressure fluid injection into a subhorizontal confined aquifer at 4.3–4.6 km depth induced >7000 earthquakes between 1991 and 2012 within once seismically quiescent Paradox Valley in Colorado, with magnitudes up to Mw 3.9. Earthquake hypocenters expanded laterally away from the well with time, defining the margins of the aquifer pressurized by injection at the well. Within 5 km of the well, alignment of earthquake hypocenters defines strikes of nine vertical fault zones. Previous studies show that these fault zones predate injection, producing left-stepping offsets in the normal faults of the Wray-Mesa fault system that cradles Paradox Valley. Hypocenters, rakes, and strikes of 2041 well-constrained focal mechanisms show that most injection-related earthquakes occur where these vertical faults intersect the pressurized aquifer. Well-defined focal mechanisms show that this induced seismicity consists of Riedel shear faults at acute angles to the strikes of these fault zones. These small faults develop an anastomosing fault structure of focal planes along each planar fault zone, as fluid injection continues, even as their hypocenters define a single planar fault zone. Failure conditions at each hypocenter are found using a fully coupled poroelastic analysis of stress induced by fluid injection, and this analysis indicates a minimum Coulomb failure condition of 0.1 MPa. This failure condition is primarily a result of aquifer pore-fluid pressurization, as almost all well-located seismicity is within the pressurized aquifer. Reducing the rate of injection and frequent well shutdowns in the second decade nearly eliminated induced seismicity, except very near the well where gradients in pressurization are the largest. Despite these decreases in failure conditions and seismicity, some fault zones continued to produce earthquakes larger than M 3 as injection continued.
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Lipovsky, Bradley Paul, Colin R. Meyer, Lucas K. Zoet, et al. "Glacier sliding, seismicity and sediment entrainment." Annals of Glaciology 60, no. 79 (2019): 182–92. http://dx.doi.org/10.1017/aog.2019.24.
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ABSTRACTThe evolution of glaciers and ice sheets depends on processes in the subglacial environment. Shear seismicity along the ice–bed interface provides a window into these processes. Such seismicity requires a rapid loss of strength that is typically ascribed to rate-weakening friction, i.e., decreasing friction with sliding or sliding rate. Many friction experiments have investigated glacial materials at the temperate conditions typical of fast flowing glacier beds. To our knowledge, however, these studies have all found rate-strengthening friction. Here, we investigate the possibility that rate-weakening rock-on-rock friction between sediments frozen to the bottom of the glacier and the underlying water-saturated sediments or bedrock may be responsible for subglacial shear seismicity along temperate glacier beds. We test this ‘entrainment-seismicity hypothesis’ using targeted laboratory experiments and simple models of glacier sliding, seismicity and sediment entrainment. These models suggest that sediment entrainment may be a necessary but not sufficient condition for the occurrence of basal shear seismicity. We propose that stagnation at the Whillans Ice Stream, West Antarctica may be caused by the growth of a frozen fringe of entrained sediment in the ice stream margins. Our results suggest that basal shear seismicity may indicate geomorphic activity.
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Fan, Gang, Jun Wang, Shunchao Qi, Gongda Lu, Xingguo Yang, and Jiawen Zhou. "Spatiotemporal Evolution of Earthquakes in Longmenshan Fault and Adjacent Area, before and after the 2008 Wenchuan Earthquake." Shock and Vibration 2021 (November 24, 2021): 1–13. http://dx.doi.org/10.1155/2021/9400276.
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Seismicity sequence following a main earthquake usually contains much meaningful information for unveiling the focal mechanism and predicting the reoccurrence interval of large earthquakes. The spatiotemporal evolution of earthquakes before and after the 2008 Wenchuan earthquake (Ms 8.0) is analysed comprehensively in this study. The frequency-magnitude relation of the 3493 earthquake events retrieved from the database of the International Seismological Centre indicates that the adopted catalogue is complete for magnitudes ≥Ms 3.4. The seismicity during the 10 years before the Wenchuan earthquake remained stable, including the magnitudes and focal depths. However, seismicity attenuated sharply in the year following the Wenchuan earthquake, and the magnitude of earthquakes before the Wenchuan earthquake decreased gradually. The area of the seismogenic zone of the 2008 Wenchuan earthquake was smaller than the earthquake stricken area. The earthquakes that occurred in the Longmenshan fault area and adjacent area in the study period were mainly shallow earthquakes. The focal depths of earthquakes in the study area became stable gradually after the Wenchuan earthquake, mainly within the range from 10 to 16 km. The earthquakes in the study area were mainly distributed with an along-dip distance of 0–20 km, and the seismicity was distributed uniformly along the fault strike.
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Jia, Ke, Shiyong Zhou, Jiancang Zhuang, et al. "Nonstationary Background Seismicity Rate and Evolution of Stress Changes in the Changning Salt Mining and Shale-Gas Hydraulic Fracturing Region, Sichuan Basin, China." Seismological Research Letters 91, no. 4 (2020): 2170–81. http://dx.doi.org/10.1785/0220200092.
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Abstract The Ms 6.0 earthquake in Changning, Sichuan, China, on 17 June 2019 was the largest recorded earthquake in the stable Sichuan basin. It occurred in a complicated region with salt mining and shale gas production. Whether this earthquake is induced raises concerns among the public and the scientific community. Furthermore, the relation between this earthquake and nearby industrial activities has also been of great interest. To address these questions, we estimated the nonstationary background seismicity rate and inverted for spatiotemporal stress changes. The results show that the background rate dramatically increased after hydraulic fracturing (HF) and remained at a high level until the present. Starting in 2005, the study region experienced an accelerating stress increase, and the rates of cumulative modified Coulomb stress changes were approximately 0.11 MPa/yr from January 2005 to January 2015 and 0.24 MPa/yr from January 2015 to December 2018. The 2019 Changning earthquake produced a stress step of 0.32 MPa. A clear difference between seismicity induced by salt mine injection and by HF is documented. Our results suggest that the Changning sequence might have been induced by long-term injection for salt production. Furthermore, the seismicity-stress inversion method provides a tool for using seismicity rate changes as a stress meter to monitor human-induced seismicity.
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Benson, Philip M., Sergio Vinciguerra, Philip G. Meredith, and R. Paul Young. "Spatio-temporal evolution of volcano seismicity: A laboratory study." Earth and Planetary Science Letters 297, no. 1-2 (2010): 315–23. http://dx.doi.org/10.1016/j.epsl.2010.06.033.
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Durand, Virginie, Stephan Bentz, Grzegorz Kwiatek, et al. "A Two-Scale Preparation Phase Preceded an Mw 5.8 Earthquake in the Sea of Marmara Offshore Istanbul, Turkey." Seismological Research Letters 91, no. 6 (2020): 3139–47. http://dx.doi.org/10.1785/0220200110.
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Abstract We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an Mw 4.7 foreshock and Mw 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure.
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Chiodini, G., C. Cardellini, F. Di Luccio, et al. "Correlation between tectonic CO2 Earth degassing and seismicity is revealed by a 10-year record in the Apennines, Italy." Science Advances 6, no. 35 (2020): eabc2938. http://dx.doi.org/10.1126/sciadv.abc2938.
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Deep CO2 emissions characterize many nonvolcanic, seismically active regions worldwide, and the involvement of deep CO2 in the earthquake cycle is now generally recognized. However, no long-time records of such emissions have been published, and the temporal relations between earthquake occurrence and tectonic CO2 release remain enigmatic. Here, we report a 10-year record (2009–2018) of tectonic CO2 flux in the Apennines (Italy) during intense seismicity. The gas emission correlates with the evolution of the seismic sequences: Peaks in the deep CO2 flux are observed in periods of high seismicity and decays as the energy and number of earthquakes decrease. We propose that the evolution of seismicity is modulated by the ascent of CO2 accumulated in crustal reservoirs and originating from the melting of subducted carbonates. This large-scale, continuous process of CO2 production favors the formation of overpressurized CO2-rich reservoirs potentially able to trigger earthquakes at crustal depth.
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Goltz, C. "Decomposing spatio-temporal seismicity patterns." Natural Hazards and Earth System Sciences 1, no. 1/2 (2001): 83–92. http://dx.doi.org/10.5194/nhess-1-83-2001.
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Abstract. Seismicity is a distributed process of great spatial and temporal variability and complexity. Efforts to characterise and describe the evolution of seismicity patterns have a long history. Today, the detection of changes in the spatial distribution of seismicity is still regarded as one of the most important approaches in monitoring and understanding seismicity. The problem of how to best describe these spatio-temporal changes remains, also in view of the detection of possible precursors for large earthquakes. In particular, it is difficult to separate the superimposed effects of different origin and to unveil the subtle (precursory) effects in the presence of stronger but irrelevant constituents. I present an approach to the latter two problems which relies on the Principal Components Analysis (PCA), a method based on eigen-structure analysis, by taking a time series approach and separating the seismicity rate patterns into a background component and components of change. I show a sample application to the Southern California area and discuss the promising results in view of their implications, potential applications and with respect to their possible precursory qualities.
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Sakkas, Vassilis, Vasilis Kapetanidis, George Kaviris, et al. "Seismological and Ground Deformation Study of the Ionian Islands (W. Greece) during 2014–2018, a Period of Intense Seismic Activity." Applied Sciences 12, no. 5 (2022): 2331. http://dx.doi.org/10.3390/app12052331.
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Seismicity in the Ionian Sea (W. Greece) is mainly generated along the Cephalonia–Lefkada Transform Fault Zone (CLTFZ) in the central Ionian, and on the northwestern termination of the Hellenic subduction margin in the south. Joint pre-, co- and post-seismic ground deformation and seismological analysis is performed at the broad Ionian area, aiming to homogeneously study the spatiotemporal evolution of the activity prior to and after the occurrence of strong (M > 6) earthquakes during the period of 2014–2018. The 2014 Cephalonia earthquakes (Mw6.1 and Mw5.9) were generated on a faulting system adjacent to CLTFZ, causing local ground deformation. The post-seismic sequence is coupled in space and time with the 2015 Lefkada earthquake (Mw6.4), which occurred on the Lefkada segment of the CLTFZ. Co-seismic displacement was recorded in the broader area. Seismicity was concentrated along the CLTFZ, while its temporal evolution lasted for several months. The 2018 Zakynthos earthquake (Mw6.7) caused regional deformation and alterations on the near-velocity field, with the seismicity rate remaining above background levels until the end of 2021. In the northern Ionian, convergence between the Apulian platform and the Hellenic foreland occurs, exhibiting low seismicity. Seismic hazard assessment revealed high PGA and PGV expected values in the central Ionian.
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Huang, Qinghua. "Seismicity Pattern Changes Prior to the 2008 Ms7.3 Yutian Earthquake." Entropy 21, no. 2 (2019): 118. http://dx.doi.org/10.3390/e21020118.
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Seismicity pattern changes that are associated with strong earthquakes are an interesting topic with potential applications for natural hazard mitigation. As a retrospective case study of the Ms7.3 Yutian earthquake, which was an inland normal faulting event that occurred on 21 March 2008, the Region-Time-Length (RTL) method is applied to the seismological data of the China Earthquake Administration (CEA) to analyze the features of the seismicity pattern changes before the Yutian earthquake. The temporal variations of the RTL parameters of the earthquake epicenter showed that a quiescence anomaly of seismicity appeared in 2005. The Yutian main shock did not occur immediately after the local seismicity recovered to the background level, but with a time delay of about two years. The spatial variations of seismic quiescence indicated that an anomalous zone of seismic quiescence appeared near the Yutian epicentral region in 2005. This result is consistent with that obtained from the temporal changes of seismicity. The above spatio-temporal seismicity changes prior to the inland normal faulting Yutian earthquake showed similar features to those reported for some past strong earthquakes with inland strike faulting or thrust faulting. This study may provide useful information for understanding the seismogenic evolution of strong earthquakes.
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Kiyashchenko, D., N. Smirnova, V. Troyan, and F. Vallianatos. "Dynamics of multifractal and correlation characteristics of the spatio-temporal distribution of regional seismicity before the strong earthquakes." Natural Hazards and Earth System Sciences 3, no. 3/4 (2003): 285–98. http://dx.doi.org/10.5194/nhess-3-285-2003.
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Abstract. Investigations of the distribution of regional seismicity and the results of numerical simulations of the seismic process show the increase of inhomogenity in spatio-temporal distribution of the seismicity prior to large earthquakes and formation of inhomogeneous clusters in a wide range of scales. Since that, the multifractal approach is appropriate to investigate the details of such dynamics. Here we analyze the dynamics of the seismicity distribution before a number of strong earthquakes occurred in two seismically active regions of the world: Japan and Southern California. In order to study the evolution of spatial inhomogeneity of the seismicity distribution, we consider variations of two multifractal characteristics: information entropy of multifractal measure generation process and the higher-order generalized fractal dimension of the continuum of the earthquake epicenters. Also we studied the dynamics of the level of spatio-temporal correlations in the seismicity distribution. It is found that two aforementioned multifractal characteristics tend to decrease and the level of spatio-temporal correlations tends to increase before the majority of considered strong earthquakes. Such a tendency can be considered as an earthquake precursory signature. Therefore, the results obtained show the possibility to use multifractal and correlation characteristics of the spatio-temporal distribution of regional seismicity for seismic hazard risk evaluation.
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Bourne, S. J., S. J. Oates, and J. van Elk. "The exponential rise of induced seismicity with increasing stress levels in the Groningen gas field and its implications for controlling seismic risk." Geophysical Journal International 213, no. 3 (2018): 1693–700. http://dx.doi.org/10.1093/gji/ggy084.
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SUMMARY Induced seismicity typically arises from the progressive activation of recently inactive geological faults by anthropogenic activity. Faults are mechanically and geometrically heterogeneous, so their extremes of stress and strength govern the initial evolution of induced seismicity. We derive a statistical model of Coulomb stress failures and associated aftershocks within the tail of the distribution of fault stress and strength variations to show initial induced seismicity rates will increase as an exponential function of induced stress. Our model provides operational forecasts consistent with the observed space–time–magnitude distribution of earthquakes induced by gas production from the Groningen field in the Netherlands. These probabilistic forecasts also match the observed changes in seismicity following a significant and sustained decrease in gas production rates designed to reduce seismic hazard and risk. This forecast capability allows reliable assessment of alternative control options to better inform future induced seismic risk management decisions.
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Mignan, Arnaud. "Static behaviour of induced seismicity." Nonlinear Processes in Geophysics 23, no. 2 (2016): 107–13. http://dx.doi.org/10.5194/npg-23-107-2016.
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Abstract. The standard paradigm to describe seismicity induced by fluid injection is to apply non-linear diffusion dynamics in a poroelastic medium. I show that the spatio-temporal behaviour and rate evolution of induced seismicity can, instead, be expressed by geometric operations on a static stress field produced by volume change at depth. I obtain laws similar in form to the ones derived from poroelasticity while requiring a lower description length. Although fluid flow is known to occur in the ground, it is not pertinent to the geometrical description of the spatio-temporal patterns of induced seismicity. The proposed model is equivalent to the static stress model for tectonic foreshocks generated by the Non-Critical Precursory Accelerating Seismicity Theory. This study hence verifies the explanatory power of this theory outside of its original scope and provides an alternative physical approach to poroelasticity for the modelling of induced seismicity. The applicability of the proposed geometrical approach is illustrated for the case of the 2006, Basel enhanced geothermal system stimulation experiment. Applicability to more problematic cases where the stress field may be spatially heterogeneous is also discussed.
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Grigoratos, Iason, Ellen Rathje, Paolo Bazzurro, and Alexandros Savvaidis. "Earthquakes Induced by Wastewater Injection, Part II: Statistical Evaluation of Causal Factors and Seismicity Rate Forecasting." Bulletin of the Seismological Society of America 110, no. 5 (2020): 2483–97. http://dx.doi.org/10.1785/0120200079.
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ABSTRACT Wastewater disposal has been reported as the main cause of the recent surge in seismicity rates in several parts of central United States, including Oklahoma. In this article, we employ the semi-empirical model of the companion article (Grigoratos, Rathje, et al., 2020) first to test the statistical significance of this prevailing hypothesis and then to forecast seismicity rates in Oklahoma given future injection scenarios. We also analyze the observed magnitude–frequency distributions, arguing that the reported elevated values of the Gutenberg–Richter b-value are an artifact of the finiteness of the pore-pressure perturbation zones and a more appropriate value would be close to 1.0. The results show that the vast majority (76%) of the seismically active blocks in Oklahoma can be associated with wastewater disposal at a 95% confidence level. These blocks experienced 84% of the felt seismicity in Oklahoma after 2006, including the four largest earthquakes. In terms of forecasting power, the model is able to predict the evolution of the seismicity burst starting in 2014, both in terms of timing and magnitude, even when only using seismicity data through 2011 to calibrate the model. Under the current disposal rates, the seismicity is expected to reach the pre-2009 levels after 2025, whereas the probability of a potentially damaging Mw≥5.5 event between 2018 and 2026 remains substantial at around 45%.
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He, Xuan, Syed Bilal Hussain Shah, Bo Wei, and Zheng Liu. "Comparison and Analysis of Network Construction Methods for Seismicity Based on Complex Networks." Complexity 2021 (February 1, 2021): 1–11. http://dx.doi.org/10.1155/2021/6691880.
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The approach of the complex network has well described seismic complex systems. In this paper, this is the first time three classical network construction methods for seismicity are compared. By using the same dataset from the Southern California Seismic Network, three networks are constructed. They all present the scale-free, small-world properties, a strength-degree correlation, and an assortative mixing feature. However, they show some differences in the hierarchical clustering feature. On observing the evolution results, three measures show a similar correlation with seismicity dynamics, but one measure shows a different result. These results show that different network construction methods will present some similarities and differences in network properties. This situation needs to be considered, especially when discussing a predictive indicator of seismicity.
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Henderson, Jeremy, and Ian Main. "A simple fracture-mechanical model for the evolution of seismicity." Geophysical Research Letters 19, no. 4 (1992): 365–68. http://dx.doi.org/10.1029/92gl00274.
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Nazarov, L. A., L. A. Nazarova, A. F. Yaroslavtsev, N. A. Miroshnichenko, and E. V. Vasil’eva. "Evolution of stress fields and induced seismicity in operating mines." Journal of Mining Science 47, no. 6 (2011): 707–13. http://dx.doi.org/10.1134/s1062739147060013.
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Hummel, Nicolas, and Serge A. Shapiro. "Nonlinear diffusion-based interpretation of induced microseismicity: A Barnett Shale hydraulic fracturing case study." GEOPHYSICS 78, no. 5 (2013): B211—B226. http://dx.doi.org/10.1190/geo2012-0242.1.
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For the successful development and operation of hydrocarbon or geothermal reservoirs, knowledge of the hydraulic transport is of crucial importance. Because fundamental physical processes of borehole fluid injections are still insufficiently understood, gathering information about transport properties of rocks under field conditions is quite difficult. However, a substantial contribution in determining the permeability evolution can be obtained by understanding the distribution of induced seismicity in space and time. We have analyzed spatio-temporal characteristics of seismicity recorded during a hydraulic fracturing treatment in the Barnett Shale. In this study, we show that the fluid-rock interaction is nonlinear. To explain corresponding spatio-temporal features of induced seismicity, we considered pore pressure diffusion based on a power-law pressure dependence of permeability. A scaling approach was used to transform clouds of hypocenters of events obtained in a hydraulically anisotropic nonlinear medium into a cloud which would be obtained in an equivalent isotropic but still nonlinear medium. For this, we used a concept of a factorized anisotropic pressure dependence of permeability and found that it is in agreement with the microseismic data under consideration. We used a numerical modeling approach to generate synthetic seismicity by solving nonlinear diffusion equations. The pore-pressure field obtained from flow rates was calibrated with the pore-pressure field computed for injection pressures. This yielded an estimate of the uniaxial storage coefficient and permitted us to compute the permeability evolution inside the fracture stimulated reservoir. Following our modeling, we generated synthetic seismicity whose spatio-temporal features are similar to the ones observed in the case study. This indicates that a nonlinear diffusion with a pressure-dependent permeability seems to provide a reasonable model of the hydraulic-fracture stimulation under consideration. A power-law pressure dependence of stimulated permeability may be a more general characteristic for shales.
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Tashlykova, Tatiana G., Tamara G. Ryashchenko, Anna A. Dolgaya, and Elena A. Lukyanova. "Induced seismicity: a geo-ecological problem of a technogenic nature." Environmental & Socio-economic Studies 4, no. 3 (2016): 21–25. http://dx.doi.org/10.1515/environ-2016-0014.
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Abstract A debatable problem of the display of induced seismicity and its causes during the construction of reservoirs (Reservoir Induced Seismicity - RIS) is considered on the basis of an analysis of various publications. This paper describes the history of the evolution of ideas about the possibility of the activation of seismic events in the zones of influence of artificial reservoirs and examples of such activation in aseismic areas, which is a medium geological response to technogenic interference (e.g. Shivajisagar reservoir in West India, Mead reservoir in the USA, Danjiangkou Reservoir in central China, Nurek reservoir in Central Asia, Chirkey reservoir in Dagestan and other). The problem and reasons of induced seismicity (RIS) are debatable. however, published examples demonstrate the existence of this process. For reservoirs with different amounts of water RIS is an inseparable component of the natural and man-made geological process. The world statistics knows cases of seismicity intensification in areas near small man-made reservoirs with low pressure levels (Belecha in former Yugoslavia, Marathon in Greece, Grandval in France). In addition, it was found that the number of local earthquakes increased after creating a cascade of three small water reservoirs (Studen Kladenets, Kardzhali and Ivaylovgrad) in the basin of The Arda river (Bulgaria). The RIS examples listed above allow us to think that it is not only the creation of large reservoirs that change (in some cases, intensifies) the local seismicity in the surrounding area. No reservoir, no matter what size it is, is insured from such geological process. At the present time there are more than 100 places in the world with displays of induced seismicity due to reservoir construction. In India there are up to eight reservoirs with these problems. Induced seismicity associated with the influence of man-made water reservoirs, causes a specific geo-ecological risks to the surrounding areas.
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Kumar, Susheel, and Nitin Sharma. "The seismicity of central and north-east Himalayan region." Contributions to Geophysics and Geodesy 49, no. 3 (2019): 265–81. http://dx.doi.org/10.2478/congeo-2019-0014.
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Abstract The Himalayan range extends upto 2400 km arc from Indus river valley in the west to Brahmaputra river valley in the east of India. Due to distinct geological structures of Himalayan seismic belt, seismicity in Himalaya is inhomogeneous. The inhomogeneity in seismicity is responsible for a number of seismic gaps in the Himalayan seismic belt. Thus Iin the present study, we proposed the study of spatial and temporal evolution of seismicity in entire central and north-east Himalayan region by using Gutenberg-Richter relationship. A detailed study on the behavior of natural seismicity in and around the seismic gap regions is carried out. The study region is segmented in four meridional regions (A) 80°E to 83.5°E, (B) 83.5°E to 87.5°E, (C) 87.5°E to 90°E and (D) 90°E to 98°E along with a fixed latitude belt. The homogeneous catalogue with 3 ≤ Mb ≤ 6.5 is used for the spatial and temporal analysis of seismicity in terms of b-value. It is find out that pockets of lower b-values are coinciding over and around stress accumulated regions. The observed low b-value before occurrence of the Nepal earthquake of 25th April, 2015 supports the argument of impending occurrence of moderate to large magnitude earthquake in Sikkim and north-east Himalayan region in future.
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Kamer, Yavor, Guy Ouillon, and Didier Sornette. "Fault network reconstruction using agglomerative clustering: applications to southern Californian seismicity." Natural Hazards and Earth System Sciences 20, no. 12 (2020): 3611–25. http://dx.doi.org/10.5194/nhess-20-3611-2020.
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Abstract. In this paper we introduce a method for fault network reconstruction based on the 3D spatial distribution of seismicity. One of the major drawbacks of statistical earthquake models is their inability to account for the highly anisotropic distribution of seismicity. Fault reconstruction has been proposed as a pattern recognition method aiming to extract this structural information from seismicity catalogs. Current methods start from simple large-scale models and gradually increase the complexity trying to explain the small-scale features. In contrast the method introduced here uses a bottom-up approach that relies on initial sampling of the small-scale features and reduction of this complexity by optimal local merging of substructures. First, we describe the implementation of the method through illustrative synthetic examples. We then apply the method to the probabilistic absolute hypocenter catalog KaKiOS-16, which contains three decades of southern Californian seismicity. To reduce data size and increase computation efficiency, the new approach builds upon the previously introduced catalog condensation method that exploits the heterogeneity of the hypocenter uncertainties. We validate the obtained fault network through a pseudo prospective spatial forecast test and discuss possible improvements for future studies. The performance of the presented methodology attests to the importance of the non-linear techniques used to quantify location uncertainty information, which is a crucial input for the large-scale application of the method. We envision that the results of this study can be used to construct improved models for the spatiotemporal evolution of seismicity.
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Bourne, Stephen J., and Stephen J. Oates. "Development of statistical geomechanical models for forecasting seismicity induced by gas production from the Groningen field." Netherlands Journal of Geosciences 96, no. 5 (2017): s175—s182. http://dx.doi.org/10.1017/njg.2017.35.
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AbstractThis paper reviews the evolution of a sequence of seismological models developed and implemented as part of a workflow for Probabilistic Seismic Hazard and Risk Assessment of the seismicity induced by gas production from the Groningen gas field. These are semi-empirical statistical geomechanical models derived from observations of production-induced seismicity, reservoir compaction and structure of the field itself. Initial versions of the seismological model were based on a characterisation of the seismicity in terms of its moment budget. Subsequent versions of the model were formulated in terms of seismic event rates, this change being driven in part by the reduction in variability of the model forecasts in this domain. Our approach makes use of the Epidemic Type After Shock model (ETAS) to characterise spatial and temporal clustering of earthquakes and has been extended to also incorporate the concentration of moment release on pre-existing faults and other reservoir topographic structures.
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Sahay, Pratap N., and Tobias M. Müller. "Diffusion in deformable porous media: Incompressible flow limit and implications for permeability estimation from microseismicity." GEOPHYSICS 85, no. 2 (2020): A13—A17. http://dx.doi.org/10.1190/geo2019-0510.1.
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Injecting fluid in a borehole often has been observed to be causally related with seismicity. The standard explanation assumes that a stress perturbation spreads out and triggers rock failure. It has been suggested that this spreading is governed by Biot’s slow P-wave, which is a diffusion process associated with compressible fluid flow. Because the diffusion constant is proportional to the permeability, the space-time evolution of seismicity is exploited to estimate the permeability. However, the more plausible scenario of incompressible fluid flow is beyond the scope of Biot’s theory. We have examined the diffusion process predicted by the de la Cruz-Spanos poroelasticity theory when the flow is incompressible. Then, the diffusion constant can be two orders of magnitude larger than the Biot diffusion constant. We have determined that seismicity-based permeability estimates strongly depend on whether the flow is compressible or incompressible. Ignoring the incompressible flow scenario might lead to an overestimation of the permeability.
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Bilal, Ahmad. "Time-seismicity evolution and seismic risk assessment of the Arabian plate." Natural Science 05, no. 09 (2013): 1019–24. http://dx.doi.org/10.4236/ns.2013.59126.
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Sarhosis, Vasilis, Dimitris Dais, Eleni Smyrou, İhsan Engin Bal, and Anastasios Drougkas. "Quantification of damage evolution in masonry walls subjected to induced seismicity." Engineering Structures 243 (September 2021): 112529. http://dx.doi.org/10.1016/j.engstruct.2021.112529.
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Savard, Geneviève, Michael G. Bostock, and Nikolas I. Christensen. "Seismicity, Metamorphism, and Fluid Evolution Across the Northern Cascadia Fore Arc." Geochemistry, Geophysics, Geosystems 19, no. 6 (2018): 1881–97. http://dx.doi.org/10.1029/2017gc007417.
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Do Nascimento, A. F., P. A. Cowie, R. J. Lunn, and R. G. Pearce. "Spatio-temporal evolution of induced seismicity at Açu reservoir, NE Brazil." Geophysical Journal International 158, no. 3 (2004): 1041–52. http://dx.doi.org/10.1111/j.1365-246x.2004.02351.x.
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Chen, Chien-chih, Ling-Yun Chiao, Ya-Ting Lee, Hui-wen Cheng, and Yih-Min Wu. "Long-range connective sandpile models and its implication to seismicity evolution." Tectonophysics 454, no. 1-4 (2008): 104–7. http://dx.doi.org/10.1016/j.tecto.2008.04.004.
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Wortel, M. J. R., and N. J. Vlaar. "Subduction zone seismicity and the thermo-mechanical evolution of downgoing lithosphere." Pure and Applied Geophysics PAGEOPH 128, no. 3-4 (1988): 625–59. http://dx.doi.org/10.1007/bf00874551.
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Pollitz, Fred F., and Camilla Cattania. "Connecting crustal seismicity and earthquake-driven stress evolution in Southern California." Journal of Geophysical Research: Solid Earth 122, no. 8 (2017): 6473–90. http://dx.doi.org/10.1002/2017jb014200.
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Karvounis, Dimitrios, and Stefan Wiemer. "A discrete fracture hybrid model for forecasting diffusion-induced seismicity and power generation in enhanced geothermal systems." Geophysical Journal International 230, no. 1 (2022): 84–113. http://dx.doi.org/10.1093/gji/ggac056.
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SUMMARY We describe a 3-D discrete fracture hybrid model (DFHM) that returns forecasts of both induced seismicity and of power generation in an Enhanced Geothermal System (EGS). Our model considers pore-pressure increase as the mechanism driving induced seismicity, similarly to other hybrid models, but it uses discrete fracture modelling for flow and heat that allows accurate and realistic transient solutions of pore pressure and temperature in fractured reservoirs. Earthquakes and flow are thus considered as closely coupled processes. In the DFHM model, the creation phase of an EGS is described as a Markovian process with a transitional probability that encapsulates the irreducible uncertainty with regards to induced seismicity. We conditioned this transitional probability on field observations from the 2006 EGS project in Basel, achieving a good match with observations of seismicity evolution. Specifically, our model effectively reproduces and explains the observed long-term exponential decay of seismicity after the well was shut in, suggesting that pore pressure diffusion in a critically stressed fractured reservoir is sufficient to explain long-lasting post-injection seismic activity as observed in Basel. We then investigate alternative injection scenarios, using Monte Carlo simulations to capture the uncertainties in fault locations and stressing conditions. We show that the number of induced events depends not only on the total injected volume but also on the injection strategy. We demonstrate that multistage injection schemes are superior to single-stage ones, since the former are associated with less seismic risk and can generate at least the same revenue in the long term.
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Vilarrasa, Víctor, Jesus Carrera, Sebastià Olivella, Jonny Rutqvist, and Lyesse Laloui. "Induced seismicity in geologic carbon storage." Solid Earth 10, no. 3 (2019): 871–92. http://dx.doi.org/10.5194/se-10-871-2019.
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Abstract. Geologic carbon storage, as well as other geo-energy applications, such as geothermal energy, seasonal natural gas storage and subsurface energy storage imply fluid injection and/or extraction that causes changes in rock stress field and may induce (micro)seismicity. If felt, seismicity has a negative effect on public perception and may jeopardize wellbore stability and damage infrastructure. Thus, induced earthquakes should be minimized to successfully deploy geo-energies. However, numerous processes may trigger induced seismicity, which contribute to making it complex and translates into a limited forecast ability of current predictive models. We review the triggering mechanisms of induced seismicity. Specifically, we analyze (1) the impact of pore pressure evolution and the effect that properties of the injected fluid have on fracture and/or fault stability; (2) non-isothermal effects caused by the fact that the injected fluid usually reaches the injection formation at a lower temperature than that of the rock, inducing rock contraction, thermal stress reduction and stress redistribution around the cooled region; (3) local stress changes induced when low-permeability faults cross the injection formation, which may reduce their stability and eventually cause fault reactivation; (4) stress transfer caused by seismic or aseismic slip; and (5) geochemical effects, which may be especially relevant in carbonate-containing formations. We also review characterization techniques developed by the authors to reduce the uncertainty in rock properties and subsurface heterogeneity both for the screening of injection sites and for the operation of projects. Based on the review, we propose a methodology based on proper site characterization, monitoring and pressure management to minimize induced seismicity.
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Pirli, Myrto, Johannes Schweitzer, Berit Paulsen, Yana V. Konechnaya, and Galina N. Antonovskaya. "Two Decades of Seismicity in Storfjorden, Svalbard Archipelago, from Regional Data." Seismological Research Letters 92, no. 5 (2021): 2695–704. http://dx.doi.org/10.1785/0220200469.
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Abstract About two decades of earthquake parametric data for the area of Storfjorden offer the best medium-term image of seismicity yet for the arctic Svalbard Archipelago. Although seismic activity is dominated by the 2008 Mw 6.1 earthquake and its compound sequence and to a far lesser extent the 2016 Mw 5.1 event near Edgeøya and its aftershocks, as well as episodic earthquake occurrence at Heerland, background levels can be established for the first time, showing that earthquake occurrence in the region shows an episodic but stable character. A certain, minimum level of coverage by the regional seismic network is crucial for seismicity to be mapped accurately in space and time, whereas the efficiency of automatic data processing algorithms also plays a role. The evolution of the network and developments in data processing suggest that images of seismicity prior to mid-2000s and at more remote regions of the Archipelago are biased. Despite restrictions, some safe conclusions can be drawn about present-day seismotectonics. The results have implications for the tectonic placement of the region and the assessment of seismic hazard.
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Carpinteri, A., G. Lacidogna, and G. Niccolini. "Acoustic emission monitoring of medieval towers considered as sensitive earthquake receptors." Natural Hazards and Earth System Sciences 7, no. 2 (2007): 251–61. http://dx.doi.org/10.5194/nhess-7-251-2007.
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Abstract. Many ancient masonry towers are present in Italian territory. In some cases these structures are at risk on account of the intensity of the stresses they are subjected to due to the high level of regional seismicity. In order to preserve this inestimable cultural heritage, a sound safety assessment should take into account the evolution of damage phenomena. In this connection, acoustic emission (AE) monitoring can be highly effective. This study concerns the structural stability of three medieval towers rising in the centre of Alba, a characteristic town in Piedmont (Italy). During the monitoring period a correlation between peaks of AE activity in the masonry of these towers and regional seismicity was found. Earthquakes always affect structural stability. Besides that, the towers behaved as sensitive earthquake receptors. Here a method to correlate bursts of AE activity in a masonry building and regional seismicity is proposed. In particular, this method permits to identify the premonitory signals that precede a catastrophic event on a structure, since, in most cases, these warning signs can be captured well in advance.
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Grigoratos, Iason, Paolo Bazzurro, Ellen Rathje, and Alexandros Savvaidis. "Time-dependent seismic hazard and risk due to wastewater injection in Oklahoma." Earthquake Spectra 37, no. 3 (2021): 2084–106. http://dx.doi.org/10.1177/8755293020988020.
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In the past decade, Oklahoma has experienced unprecedented seismicity rates, following an increase in the volumes of wastewater that are being disposed underground. In this article, we perform a probabilistic assessment of the time-dependent seismic hazard in Oklahoma and incorporate these results into an integrated seismic risk model to assess the evolution of the statewide economic losses, including a conservative forecast through 2030. Our risk model employs an injection-driven earthquake rate model, a region-specific ground motion model, a recent Vs30 map, HAZUS exposure data and updated vulnerability curves for both structural and nonstructural elements, and contents. The calculations are performed using a stochastic Monte Carlo–based approach implemented in the OpenQuake engine. The resulting seismic hazard maps illustrate the incompatibility of the regional seismic provisions with the current seismicity. In 2015, in particular, the induced seismic hazard in several places in Oklahoma was higher than along the San Andreas fault. During the peak of seismicity in 2015, the seismic risk was 275 times higher than the background level, with the vast majority of losses originating from damages to nonstructural elements and contents. Our direct economic loss estimates are in reasonable agreement with the paid insurance claims, but show significant sensitivity to the ground motion model selection. The proposed risk model, with possible regular updates on the seismicity rate forecast, can help stakeholders define acceptable production levels.
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Lee, D. K., Y. K. Jin, Y. Kim, and S. H. Nam. "Seismicity and tectonics around the northern Antarctic Peninsula from King Sejong station data." Antarctic Science 12, no. 2 (2000): 196–204. http://dx.doi.org/10.1017/s0954102000000250.
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Local earthquakes recorded at the King Sejong station (62° 13′31″S, 58° 47′07″W) from 1995–96 have been analysed to study the seismicity and tectonics around the northern Antarctic Peninsula. The nature of shallow-focused normal fault earthquakes along the South Shetland Platform is still unclear. Dominant normal fault earthquakes and minor strike-slip earthquakes in the Eastern Bransfield Basin suggest 1) ongoing extension, and 2) transtensional stress transmitted from the Antarctic–Scotia transform boundaries, the South Scotia Ridge and the Shackleton Fracture Zone. A lack of seismicity in the Central Bransfield Basin supports that active seismicity in the Eastern Bransfield Basin is not a result of subduction along the South Shetland Trench. Shallow focused earthquakes have been observed along the NW–SE trending gravity low line between the Central and the Eastern Bransfield Basins that approximately coincides with the landward projection of a fracture zone in the former Phoenix Plate.
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Baskoutas, Ioannis, George Popandopoulos, and Prasanta Chingtham. "Temporal variation of seismic parameters in the western part of the India-Eurasia plate collision zone." Research in Geophysics 1, no. 1 (2011): 3. http://dx.doi.org/10.4081/rg.2011.e3.
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We examined the temporal seismicity variation in the north-west Himalayas and the adjacent regions in relation to strong earthquake occurrences in the period 1970-2010. The aim was to promote seismic hazard assessment and to show the possibilities of strong earthquake forecasting by means of the FastBEE computer tool. The temporal variation of the seismicity is expressed in terms of three basic seismic parameters: the logarithm of the number of earthquakes logN, the seismic energy released in the mode logE2/3 and the b-value of the earthquake magnitude-frequency distribution expressed by the Gutenberg-Richter relation. Significant changes to relative mean values, forming consecutive relative minima and maxima, of the obtained temporal variation series of the seismicity parameters can be considered anomalies. These anomalies were investigated before strong (magnitude Mw≥5.6.) earthquake occurrences and were successfully correlated with 12 strong earthquakes. The mean time of the duration of the anomalies before the origin time of the impending earthquake were estimated to be equal to 3.3±1.3 years. We conclude that, in the region under study, the established correlations can be useful for the intermediate-term forecasting of strong earthquakes and that the continuous monitoring of the temporal evolution of seismicity by means of the FastBEE tool can contribute to the evaluation of the seismic hazard status in a target area. The available earthquake data and the results obtained indicate that after the beginning of 2006, the temporal variation of the seismicity does not present clear prognostic anomalies. This behavior is compatible with the absence of earthquakes with a magnitude of Mw 6.0 or more in the area examined.
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Henderson, Jeremy, Ian G. Main, Robert G. Pearce, and Mario Takeya. "Seismicity in north-eastern Brazil: fractal clustering and the evolution of thebvalue." Geophysical Journal International 116, no. 1 (1994): 217–26. http://dx.doi.org/10.1111/j.1365-246x.1994.tb02138.x.
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Hong, Tae-Kyung, Junhyung Lee, and Soung Eil Houng. "Long-term evolution of intraplate seismicity in stress shadows after a megathrust." Physics of the Earth and Planetary Interiors 245 (August 2015): 59–70. http://dx.doi.org/10.1016/j.pepi.2015.05.009.
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Wang, Wei-Hau, and Sheng-Ming Huang. "Seismicity and stress evolution in heterogeneous faults with various degrees of roughness." Tectonophysics 424, no. 3-4 (2006): 307–18. http://dx.doi.org/10.1016/j.tecto.2006.03.042.
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Astiopoulos, A. C., E. Papadimitriou, V. Karakostas, D. Gospodinov, and G. Drakatos. "SEISMICITY CHANGES DETECTION DURING THE SEISMIC SEQUENCES EVOLUTION AS EVIDENCE OF STRESS CHANGES." Bulletin of the Geological Society of Greece 43, no. 4 (2017): 1994. http://dx.doi.org/10.12681/bgsg.11390.
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The statistical properties of the aftershock occurrence are among the main issues in investigating the earthquake generation process. Seismicity rate changes during a seismic sequence, which are detected by the application of statistical models, are proved to be precursors of strong events occurring during the seismic excitation. Application of these models provides a tool in assessing the imminent seismic hazard, oftentimes by the estimation of the expected occurrence rate and comparison of the predicted rate with the observed one. The aim of this study is to examine the temporal distribution and especially the occurrence rate variations of aftershocks for two seismic sequences that took place, the first one near Skyros island in 2001 and the second one near Lefkada island in 2003, in order to detect and determine rate changes in connection with the evolution of the seismic activity. Analysis is performed through space–time stochastic models which are developed, based upon both aftershocks clustering studies and specific assumptions. The models applied are the Modified Omori Formula (MOF), the Epidemic Type Aftershock Sequence (ETAS) and the Restricted Epidemic Type Aftershock Sequence (RETAS). The modelling of seismicity rate changes, during the evolution of the particular seismic sequences, is then attempted in association with and as evidence of static stress changes
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Campbell, L. R., G. E. Lloyd, R. J. Phillips, R. C. Walcott, and R. E. Holdsworth. "Stress fields of ancient seismicity recorded in the dynamic geometry of pseudotachylyte in the Outer Hebrides Fault Zone, UK." Journal of the Geological Society 178, no. 1 (2020): jgs2020–101. http://dx.doi.org/10.1144/jgs2020-101.
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Heterogeneous sequences of exhumed fault rocks preserve a record of the long-term evolution of fault strength and deformation behaviour during prolonged tectonic activity. Along the Outer Hebrides Fault Zone (OHFZ) in NW Scotland, numerous pseudotachylytes record palaeoseismic slip events within sequences of mylonites, cataclasites and phyllonites. To date, the kinematics and controls on seismicity within the long active history of the OHFZ have been poorly constrained. Additional uncertainties over the relative location of a meteorite impact and possible pre-OHFZ brittle faulting also complicate interpretation of the diffuse seismic record. We present kinematic analyses of seismicity in the OHFZ, combining observations of offset markers, en echelon injection veins and injection vein geometry to reconstruct slip directions and stress fields. This new dataset indicates that a range of fault orientations, slip directions and slip senses hosted seismicity in the OHFZ. Such complexity requires several stress field orientations, in contrast with the NW–SE Caledonian compression traditionally attributed to frictional melting along the OHFZ, indicating that seismicity had a long-term presence across the fault zone. Persistence of strong frictional failure alongside the simultaneous development of weak fault rocks and phyllonitic shear zones in parts of the OHFZ has significant implications for understanding seismic hazard along mature continental faults.Supplementary material: Tables listing analysed orientation measurements plus further information and sensitivity testing of palaeostress analysis parameters are available at https://doi.org/10.6084/m9.figshare.c.5134797
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Cassidy, John F., Garry C. Rogers, and J. Ristau. "Seismicity in the vicinity of the SNORCLE corridors of the northern Canadian Cordillera." Canadian Journal of Earth Sciences 42, no. 6 (2005): 1137–48. http://dx.doi.org/10.1139/e04-063.
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The Slave Northern Cordillera Lithospheric Evolution (SNORCLE) corridors of the northern Cordillera sample some of the most, and least, seismically active regions of Canada. The earthquake history of this region is short. Precise determination of earthquake locations and depths is not possible even today. Nonetheless, significant gains in our knowledge of the seismicity of this region have been made in recent years from studies of historic earthquakes, microseismicity studies, and advances in waveform modelling techniques combined with broadband data that allow for determination of focal mechanisms and depths for moderate earthquakes. This article summarizes our current knowledge of the seismicity and seismic hazards across the region. These detailed analyses have shown that (i) the largest historical earthquakes have occurred in regions of ongoing microseismicity; (ii) the largest earthquakes have occurred in pairs or in swarms, suggesting that stress triggering is important in this region; (iii) the active faults are concentrated in the offshore region; (iv) there is a concentration of seismicity in the Fold and Thrust belt, several hundred kilometres from the active plate margin; and (v) there is no seismicity associated with the Quaternary volcanic zone in northern British Columbia. Potentially damaging (magnitude M ≥ 5) earthquakes can be expected every few years in the vicinity of the northern Cordillera. The Mw = 7.9 Denali, Alaska, earthquake (where Mw is the moment magnitude) was a good reminder that the effects of a large earthquake can be substantial, even hundreds of kilometres from the epicentre. Detailed studies of seismicity, earth structure, and tectonics, with the latter made possible in large part by the SNORCLE transect, will allow for informed decision-making for resource development and the design of safe structures and infrastructure in the northern Canadian Cordillera.
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Tan, Fengzhou, Honn Kao, Edwin Nissen, and Ryan Visser. "Tracking earthquake sequences in real time: application of Seismicity-Scanning based on Navigated Automatic Phase-picking (S-SNAP) to the 2019 Ridgecrest, California sequence." Geophysical Journal International 223, no. 3 (2020): 1511–24. http://dx.doi.org/10.1093/gji/ggaa387.
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SUMMARY Recent improvements in seismic data processing techniques have enhanced our ability to detail the evolution of major earthquake sequences in space and time. One such advance is new scanning algorithms that allow large volumes of waveform data to be analysed automatically, removing human biases and inefficiencies that inhibit standardized monitoring. The Seismicity-Scanning based on Navigated Automatic Phase-picking (S-SNAP) workflow has previously been shown to be capable of producing high-quality earthquake catalogues for injection-induced seismicity monitoring. In this study, we modify the original S-SNAP workflow to enable it to delineate the spatiotemporal distribution of major earthquake sequences in real time. We apply it to the 2019 Ridgecrest, southern California earthquake sequence, which culminated in an Mw 6.4 foreshock on July 4 and an Mw 7.1 main shock on July 6 and generated tens of thousands of smaller earthquakes. Our catalogue—which spans the period 2019 June 1 to July 16—details the spatiotemporal evolution of the sequence, including early foreshocks on July 1 and accelerating foreshocks on July 4, a seismicity gap before the main shock around its epicentre, seismicity on discrete structures within a broad fault zone and triggered earthquakes outside the main fault zone. We estimate the accuracy and false detection rate of the S-SNAP catalogue based on the reviewed catalogue reported by Southern California Seismic Network (SCSN) and our own visual inspection. We demonstrate the advantages of S-SNAP over a generalized automatic earthquake monitoring software, Seiscomp3, and a customized real-time earthquake information system for southern California, TriNet. In comparison, the S-SNAP catalogue contains five times more events than the Seiscomp3 catalogue and 1.4–2.2 times as many events per hour as the TriNet catalogue at most times. In addition, S-SNAP is more likely to solve phase association ambiguities correctly and provide a catalogue with consistent quality through time. S-SNAP would be beneficial to both routine network operations and the earthquake review process.