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1
Lukk, A. A., V. G. Leonova, and A. Ya Sidorin. "Revisiting the Origin of Seismicity in Fennoscandia." Izvestiya, Atmospheric and Oceanic Physics 55, no. 7 (December 2019): 743–58. http://dx.doi.org/10.1134/s000143381907003x.
2
Vasudevan, K., D. W. Eaton, and J. Davidsen. "Intraplate seismicity in Canada: a graph theoretic approach to data analysis and interpretation." Nonlinear Processes in Geophysics 17, no. 5 (October 4, 2010): 513–27. http://dx.doi.org/10.5194/npg-17-513-2010.
Анотація:
Abstract. Intraplate seismicity occurs in central and northern Canada, but the underlying origin and dynamics remain poorly understood. Here, we apply a graph theoretic approach to characterize the statistical structure of spatiotemporal clustering exhibited by intraplate seismicity, a direct consequence of the underlying nonlinear dynamics. Using a recently proposed definition of "recurrences" based on record breaking processes (Davidsen et al., 2006, 2008), we have constructed directed graphs using catalogue data for three selected regions (Region 1: 45°−48° N/74°−80° W; Region 2: 51°−55° N/77°−83° W; and Region 3: 56°−70° N/65°−95° W), with attributes drawn from the location, origin time and the magnitude of the events. Based on comparisons with a null model derived from Poisson distribution or Monte Carlo shuffling of the catalogue data, our results provide strong evidence in support of spatiotemporal correlations of seismicity in all three regions considered. Similar evidence for spatiotemporal clustering has been documented using seismicity catalogues for southern California, suggesting possible similarities in underlying earthquake dynamics of both regions despite huge differences in the variability of seismic activity.
3
Goltz, C. "Decomposing spatio-temporal seismicity patterns." Natural Hazards and Earth System Sciences 1, no. 1/2 (June 30, 2001): 83–92. http://dx.doi.org/10.5194/nhess-1-83-2001.
Анотація:
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.
4
Goertz-Allmann, Bettina P., and Stefan Wiemer. "Geomechanical modeling of induced seismicity source parameters and implications for seismic hazard assessment." GEOPHYSICS 78, no. 1 (January 1, 2013): KS25—KS39. http://dx.doi.org/10.1190/geo2012-0102.1.
Анотація:
We simulate induced seismicity within a geothermal reservoir using pressure-driven stress changes and seismicity triggering based on Coulomb friction. The result is a forward-modeled seismicity cloud with origin time, stress drop, and magnitude assigned to each individual event. Our model includes a realistic representation of repeating event clusters, and is able to explain in principle the observation of reduced stress drop and increased [Formula: see text]-values near the injection point where pore-pressure perturbations are highest. The higher the pore-pressure perturbation, the less critical stress states still trigger an event, and hence the lower the differential stress is before triggering an event. Less-critical stress states result in lower stress drops and higher [Formula: see text]-values, if both are linked to differential stress. We are therefore able to establish a link between the seismological observables and the geomechanical properties of the source region and thus a reservoir. Understanding the geomechanical properties is essential for estimating the probability of exceeding a certain magnitude value in the induced seismicity and hence the associated seismic hazard of the operation. By calibrating our model to the observed seismicity data, we can estimate the probability of exceeding a certain magnitude event in space and time and study the effect of injection depth and crustal strength on the induced seismicity.
5
Khutorskoy, Mikhail, Emil Botev, Valentina Protopopova, Aleksey Benderev, and Elena Tevelova. "Heat Flow and Seismicity in Bulgaria." Engineering Geology and Hydrogeology 34, no. 1 (2020): 53–65. http://dx.doi.org/10.52321/igh.34.1.53.
Анотація:
The study of intra-earth processes requires a comprehensive approach, which should be based on the understanding different nature and origin depth of terrestrial processes. In this regard, the problem of the relationship between seismicity and heat flow in the lithosphere is of interest. We analyzed seismic observation data in Bulgaria from 1981 to 2018 using statistical methods. A significant correlation was found between the heat flow and the earthquakes magnitude, as well as between the thickness of thermal lithosphere and the magnitude. To assess the released friction heat and hydrodynamic processes during the earth’s crust movements, it is necessary to develop theoretical models based on a comprehensive analysis of the geological structure and geophysical fields in seismically active regions.
6
Candela, Thibault, Maarten Pluymaekers, Jean-Paul Ampuero, Jan-Diederik van Wees, Loes Buijze, Brecht Wassing, Sander Osinga, Niels Grobbe, and Annemarie G. Muntendam-Bos. "Controls on the spatio-temporal patterns of induced seismicity in Groningen constrained by physics-based modelling with Ensemble-Smoother data assimilation." Geophysical Journal International 229, no. 2 (December 11, 2021): 1282–308. http://dx.doi.org/10.1093/gji/ggab497.
Анотація:
SUMMARY The induced seismicity in the Groningen gas field, The Netherlands, presents contrasted spatio-temporal patterns between the central area and the south west area. Understanding the origin of this contrast requires a thorough assessment of two factors: (1) the stress development on the Groningen faults and (2) the frictional response of the faults to induced stresses. Both factors have large uncertainties that must be honoured and then reduced with the observational constraints. Ensembles of induced stress realizations are built by varying the Poisson's ratio in a poro-elastic model incorporating the 3-D complexities of the geometries of the Groningen gas reservoir and its faults, and the historical pore pressure distribution. The a priori uncertainties in the frictional response are mapped by varying the parameters of a seismicity model based on rate-and-state friction. The uncertainties of each component of this complex physics-based model are honoured through an efficient data assimilation algorithm. By assimilating the seismicity data with an Ensemble-Smoother, the prior uncertainties of each model parameter are effectively reduced, and the posterior seismicity rate predictions are consistent with the observations. Our integrated workflow allows us to disentangle the contributions of the main two factors controlling the induced seismicity at Groningen, induced stress development and fault frictional response. Posterior distributions of the model parameters of each modelling component are contrasted between the central and south west area at Groningen. We find that, even after honouring the spatial heterogeneity in stress development across the Groningen gas field, the spatial variability of the observed induced seismicity rate still requires spatial heterogeneity in the fault frictional response. This work is enabled by the unprecedented deployment of an Ensemble-Smoother combined with physics-based modelling over a complex case of reservoir induced seismicity.
7
Paudyal, Harihar. "Fluctuation of seismic activity associated with 1999 Chamoli earthquake." Himalayan Physics 2 (July 31, 2011): 11–15. http://dx.doi.org/10.3126/hj.v2i2.5203.
Анотація:
The Chamoli earthquake of March 28, 1999 (Mb 6.6, Origin time: 19:05:12, epicenter at 30.5° N 79.4° E and Focal depth 23 km) occurred in the Himalayan front arc which caused severe damage in the region. Anomalous seismic activity associated with this recent devastating earthquake in the Central Himalaya region in an area bounded by 30.0°-31.0° N and 79.0°-80.0° E have been studied using seismicity data from 1980-2000. The preparatory zone is delineated using the temporal and the spatial distribution of earthquakes, considering the events with cutoff magnitude mb ≥ 4.3. Daily number of events as well as cumulative number of earthquake with time within the preparatory zone has been considered as basis for identification of anomalous seismicity. Accordingly four anomalous episodes: Normal/ background (N); Anomalous/ swarm (A); Precursory gap (G) and Mainshock sequence (M) are identified. It is observed that the event was preceded by well defined patterns of anomalous seismicity/ precursory swarm which was lasted for about seven month and had started about three years and four months prior to mainshock.Key words: Anomalous seismicity; Central Himalaya; Precursory swarm; Earthquake forecastThe Himalayan Physics Vol.2, No.2, May, 2011Page: 11-15Uploaded Date: 31 July, 2011
8
Valenzuela-Malebrán, Carla, Simone Cesca, Sergio Ruiz, Luigi Passarelli, Felipe Leyton, Sebastian Hainzl, Bertrand Potin, and Torsten Dahm. "Seismicity clusters in Central Chile: investigating the role of repeating earthquakes and swarms in a subduction region." Geophysical Journal International 224, no. 3 (November 21, 2020): 2028–43. http://dx.doi.org/10.1093/gji/ggaa562.
Анотація:
SUMMARY Seismicity along subduction interfaces is usually dominated by large main-shock–aftershock sequences indicative of a continuum distribution of highly coupled large asperities. In the past decades, however, the increased resolution of seismic catalogues at some subduction zone seems to indicate instead a more complex rheological segmentation of the interface. Large and megathrust earthquake ruptures seem interspersed among regions of low seismic coupling and less stress buildup. In this weaker zone, the strain is primarily released via a combination of moderate-size swarm-like seismicity and aseismic slip. Along the Chilean subduction zone, the densification of the seismic network allowed for the identification of localized seismic clusters, some of them appearing in the form of swarms before megathrust earthquakes. The origin and driving processes of this seismic activity have not yet been identified. In this study, we follow a systematic approach to characterize the seismicity at two persistent clusters in Central Chile, one located offshore Navidad and one inland, at ∼40 km depth beneath Vichuquén, which occurred throughout ∼20 yr. We investigated these clusters, by deriving high-resolution hypocentral locations and moment tensors and performing a detailed analysis of spatio-temporal patterns, magnitude and interevent time distributions of the clustered earthquakes. Both clusters are characterized by weak to moderate seismicity (below Mw 6) and stand out as clear seismicity rate and Benioff strain anomalies. At the Navidad cluster, seismicity occurs in the form of swarms, with a characteristic duration of 2–7 d and location and thrust mechanisms compatible with activity on the slab interface. Conversely, we find at Vichuquén activity dominated by thrust earthquakes occurring as repeaters on the slab interface, with a slip rate of approximately ∼5.0 cm yr−1. We attribute these clusters to local features of the subducting plate: the Navidad swarms are likely driven by repeated high pore pressure transients along a pre-fractured patch of the slab, while the seismicity at the Vichuquén cluster is interpreted as the result of a subducting seamount. Both clusters have been active before and after the Mw 8.8 Maule earthquake and persisted afterwards with the seismicity decay following the Omori law. These interactions are especially evident for the Vichuquén cluster, where the seismicity rate increased considerably after the Maule earthquake and continues to be an area of clearly elevated seismicity rate compared to its surroundings.
9
Shestopalov, I. P., and E. P. Kharin. "Relationship between solar activity and global seismicity and neutrons of terrestrial origin." Russian Journal of Earth Sciences 14, no. 1 (March 12, 2014): 1–10. http://dx.doi.org/10.2205/2014es000536.
10
De Barros, Louis, Ivan Lokmer, and Christopher J. Bean. "Origin of spurious single forces in the source mechanism of volcanic seismicity." Journal of Volcanology and Geothermal Research 262 (July 2013): 1–6. http://dx.doi.org/10.1016/j.jvolgeores.2013.06.006.
11
Chouet, Bernard A., and Phillip B. Dawson. "Origin of the pulse-like signature of shallow long-period volcano seismicity." Journal of Geophysical Research: Solid Earth 121, no. 8 (August 2016): 5931–41. http://dx.doi.org/10.1002/2016jb013152.
12
Bernal, I., and H. Tavera. "Seismic Velocity Structure in the Area of the 2007, Mw 8.0, Pisco-Peru Earthquake: Implications for the Mechanics of Subduction in the Vicinity of the Nazca Ridge." International Journal of Geophysics 2020 (November 5, 2020): 1–8. http://dx.doi.org/10.1155/2020/3874524.
Анотація:
In this study, we present a velocity model for the area of the 2007 Pisco-Peru earthquake ( Mw = 8.0 ) obtained using a double-difference tomography algorithm that considers aftershocks acquired for 6 months. The studied area is particularly interesting because it lies on the northern edge of the Nazca Ridge, in which the subduction of a large bathymetric structure is the origin of geomorphological features of the central coast of Peru. Relocated seismicity is used to infer the geometry of the subduction slab on the northern flank of the Nazca Ridge. The results prove that the geometry is continuous but convex because of the subduction of the ridge, thereby explaining the high uplift rates observed in this area. Our inferred distribution of seismicity agrees with both the coseismic and postseismic slip distributions.
13
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 (December 20, 2011): 3. http://dx.doi.org/10.4081/rg.2011.e3.
Анотація:
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.
14
Sevilgen, Volkan, Ross S. Stein, and Fred F. Pollitz. "Stress imparted by the great 2004 Sumatra earthquake shut down transforms and activated rifts up to 400 km away in the Andaman Sea." Proceedings of the National Academy of Sciences 109, no. 38 (September 4, 2012): 15152–56. http://dx.doi.org/10.1073/pnas.1208799109.
Анотація:
The origin and prevalence of triggered seismicity and remote aftershocks are under debate. As a result, they have been excluded from probabilistic seismic hazard assessment and aftershock hazard notices. The 2004 M = 9.2 Sumatra earthquake altered seismicity in the Andaman backarc rift-transform system. Here we show that over a 300-km-long largely transform section of the backarc, M≥4.5 earthquakes stopped for five years, and over a 750-km-long backarc section, the rate of transform events dropped by two-thirds, while the rate of rift events increased eightfold. We compute the propagating dynamic stress wavefield and find the peak dynamic Coulomb stress is similar on the rifts and transforms. Long-period dynamic stress amplitudes, which are thought to promote dynamic failure, are higher on the transforms than on the rifts, opposite to the observations. In contrast to the dynamic stress, we calculate that the mainshock brought the transform segments approximately 0.2 bar (0.02 MPa) farther from static Coulomb failure and the rift segments approximately 0.2 bar closer to static failure, consistent with the seismic observations. This accord means that changes in seismicity rate are sufficiently predictable to be included in post-mainshock hazard evaluations.
15
Heliani, Leni Sophia, Cecep Pratama, Parseno Parseno, Nurrohmat Widjajanti, and Dwi Lestari. "GPS-DERIVED SECULAR VELOCITY FIELD AROUND SANGIHE ISLAND AND ITS IMPLICATION TO THE MOLUCCA SEA SEISMICITY." GEOMATIKA 26, no. 2 (November 30, 2020): 107. http://dx.doi.org/10.24895/jig.2020.26-2.1199.
Анотація:
<p><em>Sangihe-Moluccas region is the most active seismicity in Indonesia. Between 2015 to 2018 there is four M6 class earthquake occurred close to the Sangihe-Moluccas region. These seismic active regions representing active deformation which is recorded on installed GPS for both campaign and continuous station. However, the origin of those frequent earthquakes has not been well understood especially related to GPS-derived secular motion. Therefore, we intend to estimate the secular motion inside and around Sangihe island. On the other hand, we also evaluate the effect of seismicity on GPS sites. Since our GPS data were conducted on yearly basis, we used an empirical global model of surface displacement due to coseismic activity. We calculate the offset that may be contained in the GPS site during its period</em><em>. </em><em>We remove the offset and estimate again the secular motion using linear least square. Hence, in comparison with the secular motion without considering the seismicity, we observe small change but systematically shifting the motion. We concluded the seismicity in the Molucca sea from 2015 to 2018 systematically change the secular motion around Sangihe Island at the sub-mm level. Finally, we obtained the secular motion toward each other between the east and west side within 1 to 5.5 cm/year displacement. </em></p>
16
Cox, R. T., and R. B. Van Arsdale. "Hotspot origin of the Mississippi embayment and its possible impact on contemporary seismicity." Engineering Geology 46, no. 3-4 (July 1997): 201–16. http://dx.doi.org/10.1016/s0013-7952(97)00003-3.
17
Pihulevskyi, P. H., O. V. Kendzera, K. V. Babii, L. B. Anisimova, and O. S. Kyryliuk. "Connection of Kryvbas tectonics with natural and technogenic seismicity." Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu, no. 2 (April 30, 2023): 5–10. http://dx.doi.org/10.33271/nvngu/2023-2/005.
Анотація:
Purpose. Studying the tectonic features of the structure of the earth’s crust of Kryvyi Rih-Kremenchuk suture zone to clarify the nature of the origin of seismic events in the Kryvbas. Methodology. To analyze and generalize the data on the Kryvbas seismicity with reference to large-scale geological and tectonic maps of exploration work. To study its tectonic structure based on geological, geophysical studies and drilling of Kryvyi Rih superdeep well. Findings. In the period 2011–2021, about 1,200 seismic events were recorded on the territory of Kryvbas, the majority of which had a minor magnitude 2.0. Among them there were identified 13 powerful industrial explosions from mb = 2.7–3.5 and 20 earthquakes of tectonic origin with mb = 2.1–4.5. Powerful explosions in mines predominantly induce earthquakes. In recent years, local earthquakes began to occur in tectonic fault zones outside the ore mining area, which indicates a change in the elastic-deformation state of the geological environment. The analysis of the attributes of local earthquakes and their locations suggests that Kryvyi Rih tectonic system and the entire eastern flank of the earth’s crust of the West Inhulets-Kryvyi Rih-Kremenchuk suture zone are geodynamically active structures, where the processes of thrust and shear tectonics are also observed on a recent geological time scale. Originality. A detailed analysis of the earthquakes shows that some of them occur at significant depths in the zones of tectonic faults outside of Kryvbas. At the same time, faults in separate directions are activated, where brittle deformations and viscous-plastic formations are manifested in the past geological time. The location of local earthquakes made it possible to single out two sections and five linear zones of seismic activity in the region. Practical value. Based on the results from this research it is possible to create an applied model of the tectonic section of the earth’s crust to solve the problems of evolution and geodynamics of the lithosphere of the Ukrainian shield, mountain geology and to optimize mining. The identified faults of active inherited development are important in determining the development paths for quarries and mines in Kryvbas.
18
Güvercin, Sezim Ezgi, Hayrullah Karabulut, A. Özgün Konca, Uğur Doğan, and Semih Ergintav. "Active seismotectonics of the East Anatolian Fault." Geophysical Journal International 230, no. 1 (February 4, 2022): 50–69. http://dx.doi.org/10.1093/gji/ggac045.
Анотація:
SUMMARY The East Anatolian Fault (EAF) is a 700-km-long left-lateral transform fault located between the Anatolian and Arabian plates. The proximity of the Euler Pole to the Arabia–Anatolia Plate boundary leads to rapid changes in plate velocity along the boundary, which is manifested by the decreasing slip rates from east (10 mm yr–1) to west (∼1–4 mm yr–1). The EAF displays heterogeneous seismicity patterns with seismic gaps, localized clusters and broad diffuse zones. In this study, in order to understand the origin of these complexities and quantify the seismic hazard along the EAF, we present an improved seismicity catalogue with more than 26 000 earthquakes and 160 focal mechanisms from regional moment tensor inversion between 2007 and 2020. The focal mechanisms and seismicity show that the EAF dips towards north and forms a well-defined plate boundary in the east between Palu and Çelikhan with almost pure left-lateral motion. Further west, the boundary becomes broader with activity along subparallel faults. Focal mechanisms show heterogeneous stress orientations in consistence with geodetically determined strain rate field. The stress orientations show a transition from strike-slip to extension towards the west of Çelikhan. Amongst all segments of EAF, the Pütürge segment, which holds the near-repeating earthquakes in the vicinity of the nucleation of the 2020 Mw 6.8 earthquake, is distinguished with its steady and high rate of seismicity. Further east, the neighbouring Palu segment is characterized by several distinct moderate earthquakes. We do not observe any change in the seismicity rate on these segments of the EAF following large earthquakes. In order to quantify the seismic hazard along the EAF, we calculate the recurrence time and maximum magnitude for each segment by using an extended seismicity catalogue of 150 yr including the large historical earthquakes and the geodetic strain rate. The results show ∼150 yr recurrence time with Mmax∼6.7–7.0 along the seismically active Palu and Pütürge segments on the east, while relatively silent western segments yield longer recurrence times; 237–772 for Pazarcık and 414–917 for Amanos segments with slightly larger magnitudes (Mmax ∼7–7.4). We infer that the seismicity patterns and strain-rate field along the EAF are shaped by several factors such as strong geometrical irregularities, heterogeneous coupling and complex plate motion leading to rapid change of fault slip rate.
19
Fahmi, M. N., A. Realita, H. Risanti, T. Prastowo, and M. Madlazim. "Vulnerability in the Java northen region in association with earthquake sources of tectonic origin." Journal of Physics: Conference Series 2596, no. 1 (September 1, 2023): 012041. http://dx.doi.org/10.1088/1742-6596/2596/1/012041.
Анотація:
Abstract While threats from the subduction zone off the Java south coast remain persistent, potential sources of a tectonic earthquake centered in the Java northern areas come into play. Despite their enigmatic presence and a clear shift of the sources from the mainland to the north from hypocentre relocation studies, this poses a danger to the community in the Java northern coastlines, increasing vulnerability to earthquake and tsunami hazards. The main aim of this study is thus to evaluate seismic hazards and corresponding analysis, hence assessing vulnerability with respect to the presence of active faults in the northern regions. The methods used here included a-value and b-value calculations inferred from seismogenic zonation made available for the study area and source mechanism determination derived from seismic inversion for two recent events recorded at the Java Sea. The results revealed that the a-value reached 8.55 in Zone 1, reflecting a high seismicity rate over the northern areas of West Java and Banten provinces, and the b-value was about 0.8 in Central Java and East Java, implying a relatively high-stress tectonic regime. The moment tensor solutions yielded sizes M w 6.7 at a depth of 539 km and M w 7.0 at a depth of 594 km with a major double-couple component for the normal faulting types of mechanism, consistent with reference. The results suggest the significance of awareness of seismic threats possible to occur in the Java northern regions; hence more investigations into detailed seismicity in the regions of interest for future research direction.
20
Azeez, K. K. Abdul, Kapil Mohan, K. Veeraswamy, B. K. Rastogi, Arvind K. Gupta, and T. Harinarayana. "Lithospheric resistivity structure of the 2001 Bhuj earthquake aftershock zone." Geophysical Journal International 224, no. 3 (November 24, 2020): 1980–2000. http://dx.doi.org/10.1093/gji/ggaa556.
Анотація:
SUMMARY The Bhuj area, in the Kutch region of western India, is a unique intraplate seismic zone in the world where aftershock activity associated with a large magnitude earthquake (7.7 Mw Bhuj earthquake on 26 January 2001) has persisted over a decade and up till today. We studied the lithospheric resistivity structure of the Bhuj earthquake aftershock zone to gain more insight into the structure and processes influencing the generation of intraplate seismicity in broad and, in particular, to detect the deep origin and upward migration channels of fluids linked to the crustal seismicity in the area. A lithospheric resistivity model deduced from 2-D and 3-D inversions of long-period magnetotelluric (MT) data shows low resistive lithospheric mantle, which can be best explained by a combination of a small amount of interconnected melts and aqueous fluid in the upper mantle. The MT model also shows a subvertical modestly conductive channel, spatially coinciding with the Kutch Mainland Fault, which we interpret to transport fluids from the deep lithosphere to shallow crust. We infer that pore pressure buildup aids to achieve the critical stress conditions for rock failure in the weak zones, which are pre-stressed by the compressive stress regime generated by ongoing India–Eurasia collision. The fluidized zone in the upper mantle beneath the area perhaps provides continuous fluid supply, which is required to maintain the critical stress conditions within the seismogenic crust for continued seismicity.
21
SHUKLA, H. P., R. S. DATTATRAYAM, and A. K. BHATNAGAR. "Seismicity of region around dams in North West India." MAUSAM 63, no. 2 (December 16, 2021): 261–74. http://dx.doi.org/10.54302/mausam.v63i2.1399.
Анотація:
The collision of Indian and Eurasian continents caused large scale deformation and high seismicityof vast areas of both continents in the geological history. The North-West portion of the Himalayan arc which is lyingunder the rupture zones of Kangra earthquake of 1905, Uttarkashi earthquake of 1991 and Chamoli earthquake in 1999,has experienced many earthquakes of magnitude 6 and above. The region of North-West India between 30.0º - 35.0ºNorth and 73.0º - 79.0º East is, therefore, under intense investigations by various scientists since the origin of theHimalayas. India Meteorological Department had opened thirteen seismic observatories in early sixties for monitoringof earthquake activities in and around Bhakra, Pong, Pandoh dams in Punjab / Himachal Pradesh and Salal dam inJ&K on specific demand of the dam authorities. These observatories have recorded the earthquakes occurred in thisregion having magnitude even less than 2. The data collected for the last two decades is very useful for the scientiststo investigate seismicity and tectonics of the Himalayas. The present study could locate the regions which areseismically most active and also the region of seismic gap. Thus present study confirms association of seismic activityin the region with two major fault systems called Main Boundary Thrust (MBT) and Main Central Thrust (MCT).Comparative seismic activity within 100 km from each dam, reveal that most active region was around Pong followed byPandoh, Bhakra and Salal dams. The temporal variation of b-values for the whole period also shows that low b-valueanomalies are usually followed by large earthquakes of M > 5.5. No definite conclusions could be drawn with regard tothe relationship between the observed seismic activity around the dam sites with the corresponding water levelfluctuations in the reservoirs.
22
Jansen, Jan-Dirk, and Rien Herber. "Research into induced seismicity in the Groningen field – further studies." Netherlands Journal of Geosciences 96, no. 5 (December 2017): s279—s284. http://dx.doi.org/10.1017/njg.2017.21.
Анотація:
AbstractFurther research into seismicity caused by natural gas production from the Groningen field is necessary to improve the assessment of seismic risk and develop means to control and reduce it. Research into subsurface aspects is primarily of relevance to assess the seismic hazard component in the cause-and-effect chain that governs the seismic risk. It requires a wide range of research activities that can be broadly classified as follows: •Increasing understanding of the physical mechanisms that govern production-induced seismicity, in particular source mechanisms, compaction behaviour, propagation of energy to the surface, and the effects of fluctuating production.•Reducing uncertainty by acquiring additional field data to improve statistical inference, and developing statistical methods and procedures that can cope with the non-stationary nature of the process.•Developing tools and techniques to improve risk management, and support operational control and policy measures under uncertainty.An essential requirement for further research will be the possibility of developing competing theories for many aspects of the modelling chain. This requires an overall hazard and risk assessment methodology that can accommodate multiple models, and an organisational structure that facilitates the comparison of competing approaches while safeguarding their independent development. This will have to be supported by the availability of reliable data via shared databases. Finally, the scientific community should be prepared to make a major effort to translate their research results into popular scientific versions in order to keep stakeholders abreast of progressive insight into the origin, predictability and prevention of induced seismicity.
23
BODRI, B. "A FRACTAL MODEL FOR SEISMICITY AT IZU-TOKAI REGION, CENTRAL JAPAN." Fractals 01, no. 03 (September 1993): 539–46. http://dx.doi.org/10.1142/s0218348x93000563.
Анотація:
Fractal approach has been applied to investigate regional seismicity at the Izu peninsula—Tokai area, Central Japan. The frequency-magnitude distribution of earthquakes, distribution of epicenters, origin times of earthquakes, the fracture fault system in the region have been considered, and the fractal dimensions corresponding to them were calculated. A good correspondence in the fractal dimension values was found. The frequency-magnitude distribution in the area shows a fractal dimension of 1.28, whilst D=1.15±0.18 is representative of the geometry of the distribution of earthquake epicenters. The fractal dimension of faults for the Izu peninsula is found to be 1.16±0.04, and in the whole Izu-Tokai region, values 1.1<D<1.3 are characteristic. The temporal distribution of earthquakes yields a fractal dimension of 0.51±0.03, which indicates a relatively weak clustering of events in time. Independent autocorrelation analysis also shows that the earthquakes in the area of study occur to a large extent statistically independent. The general conclusion is that crustal deformation in the Izu-Tokai region occurs on a scale-invariant matrix faults. The behavior of the system is controlled by a single parameter, the fractal of dimension.
24
Zhou, Huiling, Xiaocheng Zhou, Hejun Su, Ying Li, Fengli Liu, Shupei Ouyang, Yucong Yan, and Ronglong Bai. "Hydrochemical Characteristics of Earthquake-Related Thermal Springs along the Weixi–Qiaohou Fault, Southeast Tibet Plateau." Water 14, no. 1 (January 5, 2022): 132. http://dx.doi.org/10.3390/w14010132.
Анотація:
The Weixi–Qiaohou Fault (WQF) is considered an important zone of the western boundary of the Sichuan–Yunnan block, and its seismicity has attracted much attention after a series of moderate–strong earthquakes, especially the Yangbi Ms6.4 earthquake that occurred on 21 May 2021. In the present research, we investigate major and trace elements, as well as hydrogen and oxygen isotopes, of 10 hot springs sites located along the WQF, which are recharged by infiltrated precipitation from 1.9 to 3.1 km. The hydrochemical types of most analyzed geothermal waters are HCO3SO4-Na, SO4Cl-NaCa, and SO4-Ca, proving that they are composed of immature water and thus are characterized by weak water–rock reactions. The heat storage temperature range was from 44.1 °C to 101.1 °C; the circulation depth was estimated to range between 1.4 and 4.3 km. The results of annual data analysis showed that Na+, Cl−, and SO42− in hot springs decreased by 11.20% to 23.80% north of the Yangbi Ms5.1 earthquake, which occurred on 27 March 2017, but increased by 5.0% to 28.45% to the south; this might be correlated with the difference in seismicity within the fault zone. The results of continuous measurements of NJ (H1) and EYXX (H2) showed irregular variation anomalies 20 days before the Yangbi Ms6.4 earthquake. In addition, Cl− concentration is more sensitive to near-field seismicity with respect to Na+ and SO42−. We finally obtained a conceptual model on the origin of groundwater and the hydrogeochemical cycling process in the WQF. The results suggest that anomalies in the water chemistry of hot spring water can be used as a valid indicator of earthquake precursors.
25
Menant, Armel, Samuel Angiboust, Patrick Monié, Onno Oncken, and Jean-Michel Guigner. "Brittle deformation during Alpine basal accretion and the origin of seismicity nests above the subduction interface." Earth and Planetary Science Letters 487 (April 2018): 84–93. http://dx.doi.org/10.1016/j.epsl.2018.01.029.
26
Zahibo, N., and E. N. Pelinovsky. "Evaluation of tsunami risk in the Lesser Antilles." Natural Hazards and Earth System Sciences 1, no. 4 (December 31, 2001): 221–31. http://dx.doi.org/10.5194/nhess-1-221-2001.
Анотація:
Abstract. The main goal of this study is to give the preliminary estimates of the tsunami risks for the Lesser Antilles. We investigated the available data of the tsunamis in the French West Indies using the historical data and catalogue of the tsunamis in the Lesser Antilles. In total, twenty-four (24) tsunamis were recorded in this area for last 400 years; sixteen (16) events of the seismic origin, five (5) events of volcanic origin and three (3) events of unknown source. Most of the tsunamigenic earthquakes (13) occurred in the Caribbean, and three tsunamis were generated during far away earthquakes (near the coasts of Portugal and Costa Rica). The estimates of tsunami risk are based on a preliminary analysis of the seismicity of the Caribbean area and the historical data of tsunamis. In particular, we investigate the occurrence of historical extreme runup tsunami data on Guadeloupe, and these data are revised after a survey in Guadeloupe.
27
GAJEK, W., J. TROJANOWSKI, and M. MALINOWSKI. "Automating long-term glacier dynamics monitoring using single-station seismological observations and fuzzy logic classification: a case study from Spitsbergen." Journal of Glaciology 63, no. 240 (May 8, 2017): 581–92. http://dx.doi.org/10.1017/jog.2017.25.
Анотація:
ABSTRACTRetreating glaciers are a consequence of a warming climate. Thus, numerous monitoring campaigns are being carried out to increase understanding of this on-going process. One phenomenon related to dynamic glacial changes is glacier-induced seismicity; however, weak seismic events are difficult to record due to the sparse seismological network in arctic areas. We have developed an automatic procedure capable of detecting glacier-induced seismic events using records from a single permanent seismological station. To distinguish between glacial and non-glacial signals, we developed a fuzzy logic algorithm based on the signal frequency and energy flow analysis. We studied the long-term changes in glacier-induced seismicity in Hornsund (southern Spitsbergen) and in Kongsfjorden (western Spitsbergen). We found that the number of detected glacial-origin events in the Hornsund dataset over the years 2013-14 has doubled. In the Kongsfjorden dataset, we observed a steady increase in the number of glacier-induced events with each year. We also observed that the seasonal event distribution correlates best with 1 month lagged temperatures, and that extreme rain events can intensify seismic emissions. Our study demonstrates the possibility of using long-term seismological observations from a single permanent station to automatically monitor the dynamic activity of nearby glaciers and retrieve its characteristic features.
28
Kaban, Mikhail K., Sami El Khrepy, and Nassir Al-Arifi. "Density structure and isostasy of the lithosphere in Egypt and their relation to seismicity." Solid Earth 9, no. 4 (July 6, 2018): 833–46. http://dx.doi.org/10.5194/se-9-833-2018.
Анотація:
Abstract. A joint analysis of the new satellite–terrestrial gravity field model with recent data on the crustal structure and seismic tomography was conducted to create an integrative model of the crust and upper mantle and to investigate the relation of the density structure and the isostatic state of the lithosphere to the seismicity of Egypt. We identified the distinct fragmentation of the lithosphere of Egypt in several blocks. This division is closely related to the seismicity patterns in this region. The relatively dense and strong lithosphere in the Nile Delta limits the seismic activity within this area, while earthquakes are mainly associated with the boundaries of this block. In the same way, the relatively strong lithosphere in the Isthmus of Suez and northern Mediterranean prevents the Gulf of Suez from opening further. The central part of Egypt is generally characterized by an increased density of the mantle, which extends to the Mediterranean at a depth of 100 km. This anomaly deepens southward to Gilf Kebir and eastward to the Eastern Desert. The average density of the crystalline crust is generally reduced in this zone, indicating the increased thickness of the upper crust. The low-density anomaly under the northern Red Sea is limited to 100–125 km, confirming the passive origin of the extension. Most of the earthquakes occur in the crust and uppermost mantle in this structure due to the hot and weak upper mantle underneath. Furthermore, an asymmetric lithosphere structure is observed across the northern Red Sea. The isostatic anomalies show the fragmentation of the crust of Sinai with the high-density central block. Strong variations in the isostatic anomalies are correlated with the high level of seismicity around Sinai. This tendency is also evident in the northern Red Sea, east of the Nile Valley, and in parts of the Western Desert.
29
Kalpna and R. Chander. "On some microearthquakes near Tarbela reservoir during three low water stands." Bulletin of the Seismological Society of America 87, no. 1 (February 1, 1997): 265–71. http://dx.doi.org/10.1785/bssa0870010265.
Анотація:
Abstract Detailed 3D stress analyses with a simulated model of Tarbela reservoir indicate that most nearby seismogenic faults inferred from observations of preimpoundment seismicity in the region should be stabilized even when the reservoir has low water levels during dry seasons. We hypothesize that the hypocenters of some microearthquakes occurring close to the reservoir during dry seasons of 1977, 1980, and 1981 were located on those of the above faults that are destabilized by accumulation of broadly north-south horizontal compressive stresses of plate tectonic origin. An order of magnitude analysis shows that the rate of accumulation of these stresses may be sufficiently rapid to overcome the stability imparted to the seismogenic faults by the Tarbela reservoir.
30
Stemberk, Josef, Miloš Briestenský, and Stefan Cacoń. "The recognition of transient compressional fault slow−slip along the northern shore of Hornsund Fjord, Sw Spitsbergen, Svalbard." Polish Polar Research 36, no. 2 (June 1, 2015): 109–23. http://dx.doi.org/10.1515/popore-2015-0007.
Анотація:
AbstractThis paper presents the results of direct 3−D fault displacement monitoring along the northern shore of Hornsund Fjord, SW Spitsbergen, Svalbard. The fault displacements have been recorded using three permanently installed optical−mechanical crack gauges since 2009. The monitoring data from all three sites provided evidence for a remarkable slip event that lasted from September 2011 to May 2012. The cause is discussed in some detail with consideration given to both exogenic (temperature changes, surface processes) and endogenic processes (isostatic rebound and regional seismicity). It is proposed that transient fault slips recorded had a tectonic origin and were caused by approximately W−E oriented compression corresponding to regional compression in the Svalbard area.
31
Hernández-Marín, M., N. González-Cervantes, J. Pacheco-Martínez, and D. H. Frías-Guzmán. "Discussion on the origin of surface failures in the Valley of Aguascalientes, México." Proceedings of the International Association of Hydrological Sciences 372 (November 12, 2015): 235–38. http://dx.doi.org/10.5194/piahs-372-235-2015.
Анотація:
Abstract. Surface failures have been observed in the valley of Aguascalientes since the early 1980's. Although, groundwater pumping began in the early 1950's but became intensive until the late 1970's, when many of the surface failures appeared. For this reason, surface deformation (surface failures and land subsidence) has been associated to groundwater withdrawal. Recent observations, however, suggest that some of these surface discontinuities are the result of natural geologic stresses rather than those associated groundwater decline, at least in its origin. Geologically, this valley is a tectonic graben flanked by two north-to-south trending normal faults, and seismicity of low intensity has been detected into the valley evidencing that the study area is seismically active. In this work, we present and discuss evidence showing tectonic discontinuities on the surface or at a shallow depth. Evidence presented in this investigation brings up uncertainty about the purely pumping-induced origin of fissuring in the valley, and allows addressing some key questions, for instance, are the surface failures caused by the combined stresses of pumping and tectonism? Is the current tectonism sufficient to cause some surface or deep failures?
32
Amitrano, David, Stéphane Gaffet, Jean-Philippe Malet, and Olivier Maquaire. "Understanding mudslides through micro-seismic monitoring: the Super-Sauze (South-East French Alps) case study." Bulletin de la Société Géologique de France 178, no. 2 (March 1, 2007): 149–57. http://dx.doi.org/10.2113/gssgfbull.178.2.149.
Анотація:
Abstract The macroscopic deformation of rocks, at scales ranging from laboratory samples (cm) to rock hillslopes and earth crust (hm to km), is associated with local irreversible processes (cracks/faults propagation and shearing). These movements involve propagation of acoustic waves, which can be observed by remote sensing. Seismic monitoring during strain progression can help our understanding of rock behaviour and lead to the recognition of failure precursors. Although of significant potential, this observational tool has had only limited application in the study of gravitational instabilities such as landslides. This paper presents seismic monitoring data acquired on a mudslide located in the South French Alps. Results show that recordable seismicity exists in the frequency range of 0.01 Hz to 10 Hz associated with landslide deformation. Acceleration of landslide movement is controlled by rainfall and appears to be well correlated with seismic activity. The origin of the seismicity is attributed to shearing of the moving mass at the interface with the in-situ stable bedrock. Spectral analysis of the seismic wave reveals that the range 0.1–1 Hz is the most sensitive to the variations in landslide velocity. The results emphasize the strong potential of seismic monitoring for improving our understanding of mechanisms controlling rock mass deformation and gravitational instability. The determination of operational failure precursors based on seismic monitoring has yet to be achieved but remains a major target of future research.
33
Wallace, Laura M. "Slow Slip Events in New Zealand." Annual Review of Earth and Planetary Sciences 48, no. 1 (May 30, 2020): 175–203. http://dx.doi.org/10.1146/annurev-earth-071719-055104.
Анотація:
Continuously operating global positioning system sites in the North Island of New Zealand have revealed a diverse range of slow motion earthquakes on the Hikurangi subduction zone. These slow slip events (SSEs) exhibit diverse characteristics, from shallow (<15 km), short (<1 month), frequent (every 1–2 years) events in the northern part of the subduction zone to deep (>30 km), long (>1 year), less frequent (approximately every 5 years) SSEs in the southern part of the subduction zone. Hikurangi SSEs show intriguing relationships to interseismic coupling, seismicity, and tectonic tremor, and they exhibit a diversity of interactions with large, regional earthquakes. Due to the marked along-strike variations in Hikurangi SSE characteristics, which coincide with changes in physical characteristics of the subduction margin, the Hikurangi subduction zone presents a globally unique natural laboratory to resolve outstanding questions regarding the origin of episodic, slow fault slip behavior. ▪ New Zealand's Hikurangi subduction zone hosts slow slip events with a diverse range of depth, size, duration, and recurrence characteristics. ▪ Hikurangi slow slip events show intriguing relationships with seismicity ranging from small earthquakes and tremor to larger earthquakes. ▪ Slow slip events play a major role in the accommodation of plate motion at the Hikurangi subduction zone. ▪ Many aspects of the Hikurangi subduction zone make it an ideal natural laboratory to resolve the physical processes controlling slow slip.
34
Potirakis, S. M., G. Minadakis, and K. Eftaxias. "Relation between seismicity and pre-earthquake electromagnetic emissions in terms of energy, information and entropy content." Natural Hazards and Earth System Sciences 12, no. 4 (April 25, 2012): 1179–83. http://dx.doi.org/10.5194/nhess-12-1179-2012.
Анотація:
Abstract. In this paper we show, in terms of Fisher information and approximate entropy, that the two strong impulsive kHz electromagnetic (EM) bursts recorded prior to the Athens earthquake (EQ) (7 September 1999, magnitude 5.9) present compatibility with the radar interferometry data and the seismic data analysis, which indicates that two fault segments were activated during Athens EQ. The calculated Fisher information and approximate entropy content ratios closely follow the radar interferometry result that the main fault segment was responsible for 80 % of the total energy released, while the secondary fault segment for the remaining 20 %. This experimental finding, which appears for the first time in the literature, further enhances the hypothesis for the seismogenic origin of the analyzed kHz EM bursts.
35
Chen, Chen, Hersh Gilbert, Christopher Andronicos, Michael W. Hamburger, Timothy Larson, Stephen Marshak, Gary L. Pavlis, and Xiaotao Yang. "Shear velocity structure beneath the central United States: implications for the origin of the Illinois Basin and intraplate seismicity." Geochemistry, Geophysics, Geosystems 17, no. 3 (March 2016): 1020–41. http://dx.doi.org/10.1002/2015gc006206.
36
Trifonov, B. A., and V. V. Sevost'yanov. "SPECIFICS OF PERFORMING SEISMIC MICROZONING IN THE URBANIZED COASTAL AREA OF GELENDZHIK CITY FOR HIGH-RISE CONSTRUCTION." Engineering survey 12, no. 5-6 (August 16, 2018): 82–90. http://dx.doi.org/10.25296/1997-8650-2018-12-5-6-82-90.
Анотація:
The initial (background) seismicity of the territory of Gelendzhik with the high responsibility buildings projected for construction of (35-storey towers 123 meters high) is equal to 9 points according to the Map of General Seismicity of Russia (OSR-2015(B)) with the period of recurrence of tremors 1 time per 1000 years. The purpose of the study was to obtain the parameters of predictive seismic impacts for the site of the proposed construction taking into account regional seismotectonic and local seismic soil conditions. The influence of ground conditions on the on the seismicity of the research site was estimated when the bedrock in the Black Sea coast of the Caucasus, as a rule, lies not deep (several meters) from the surface and overlapping Quaternary sediments are flooded. Based on the result of vertical seismic profiling (VSP), a generalized geoseismic condition for the whole site was given. To determine the seismic intensity increment ΔI by the method of seismic rigidities comparison, the weighted average values of the S-waves velocities and the thickness of the soils up to the boundary of the reference soil were used in the calculations. Based on the obtained geoseismic model (results of engineering-geological and seismic studies), the NERA program calculated the parameters of seismic impacts from the most hazardous zones of origin of seismic foci (ASF) taking into account the initial seismic impacts in the territory of Gelendzhik and the results of seismic microzoning. It was found that the highest values of maximum accelerations at the studied site are caused by foci from the Mikhailovskaya and Gelendhizkskaya ASF zones; and the lower values are expected from outbreaks from the Tyapsinskaya and Akhtyrskaya ASF zones. To calculate the seismic load on the projected structures, it is proposed to use one set of synthesized accelerograms (X, Y, Z) simulating the impact from different PSF zones, which contain the entire set of vibration periods and cover the whole range of maximal velocities dangerous for the studied areas. The analysis obtained data shows good convergence of the seismic microzoning data obtained by the calculation method and seismic rigidity method.
37
Camelbeeck, Thierry, Koen Van Noten, Thomas Lecocq, and Marc Hendrickx. "The damaging character of shallow 20th century earthquakes in the Hainaut coal area (Belgium)." Solid Earth 13, no. 3 (March 9, 2022): 469–95. http://dx.doi.org/10.5194/se-13-469-2022.
Анотація:
Abstract. The present study analyses the impact and damage of shallow seismic activity that occurred from the end of the 19th century until the late 20th century in the coal area of the Hainaut province in Belgium. This seismicity is the second-largest source of seismic hazard in north-western Europe after the Lower Rhine Embayment. During this period, five earthquakes with moment magnitudes (Mw) around 4.0 locally caused moderate damage to buildings corresponding to maximum intensity VII on the European Macroseismic Scale 1998 (EMS-98). Reviewing intensity data from the official macroseismic surveys held by the Royal Observatory of Belgium (ROB), press reports and contemporary scientific studies resulted in a comprehensive macroseismic intensity dataset. Using this dataset, we created macroseismic maps for 28 earthquakes, established a new Hainaut intensity attenuation model and a relationship linking magnitude, epicentral intensity and focal depth. Using these relationships, we estimated the location and magnitude of pre-1985 earthquakes that occurred prior to deployment of the modern digital Belgian seismic network. This resulted in a new updated earthquake catalogue for the Hainaut area for the 1887–1985 period, including 124 events. A comparison with other areas worldwide where currently similar shallow earthquake activity occurs suggests that intensity attenuation is strong in Hainaut. This high attenuation and our analysis of the cumulative effect of the Hainaut seismicity indicate that current hazard maps overestimate ground motions in the Hainaut area. This reveals the need to use more appropriate ground motion models in hazard issues. Another strong implication for earthquake hazard comes from the reliability of the computed focal depths that helps clarifying the hypotheses about the origin of this seismicity. Some events were very shallow and occurred near the surface up to a depth not exceeding 1 km, suggesting a close link to mining activities. Many events, including the largest shallow events in the coal area before 1970, occurred at depths greater than 2 km, which would exclude a direct relationship with mining, but still might imply a triggering causality. A similar causality can also be questioned for other events that occurred just outside of the coal area since the end of the mining works.
38
Klaasen, Sara, Solvi Thrastarson, Yeşim Çubuk-Sabuncu, Kristín Jónsdóttir, Lars Gebraad, Patrick Paitz, and Andreas Fichtner. "Subglacial volcano monitoring with fibre-optic sensing: Grímsvötn, Iceland." Volcanica 6, no. 2 (September 5, 2023): 301–11. http://dx.doi.org/10.30909/vol.06.02.301311.
Анотація:
We present a distributed acoustic sensing (DAS) experiment at Grímsvötn, Iceland. This is intended to investigate volcano-microseismicity at Grímsvötn specifically, and to assess the suitability of DAS as a subglacial volcano monitoring tool in general. In spring 2021, we trenched a 12 km long fiber-optic cable into the ice sheet around and within the caldera, followed by nearly one month of continuous recording. An image processing algorithm that exploits spatial coherence in DAS data detects on average ~100 events per day, almost 2 orders of magnitude more than in the regional earthquake catalog. A nonlinear Bayesian inversion reveals the presence of pronounced seismicity clusters, containing events with magnitudes between −3.4 and 1.7. Their close proximity to surface volcanic features suggests a geothermal origin. In addition to painting a fine-scale picture of seismic activity at Grímsvötn, this work confirms the potential of DAS in subglacial volcano monitoring.
39
Niyogi, Shankho, Abhijit Ghosh, Abhash Kumar, and Richard W. Hammack. "Tremor signals during fluid injection are generated by fault slip." Science 381, no. 6657 (August 4, 2023): 553–58. http://dx.doi.org/10.1126/science.adh1331.
Анотація:
Seismic tremor signals, also known as long-period, long-duration signals, have been reported in several locations where fluid injection for enhanced oil and gas exploration is taking place. However, the origin of these signals remains poorly constrained. We studied seismic tremor signals in Wellington Field, Kansas, using a seismic array during a carbon dioxide injection program. We show that these signals are generated below the surface during the time of carbon dioxide injection. They have a distinct spectral signature, similar to those observed in glacial and volcanic environments. The tremor sources are located near the injection site and aligned with preexisting faults. Modeling results imply that such tremors are generated by frictional slip on fault. These observations may reveal an important deformation mode, which is useful for studying associated stress, seismicity, and triggering, as well as for tracking fault activities during injection operations of all fluids, including supercritical carbon dioxide.
40
Shcherbina, S. V., P. G. Pigulevskyi, I. Yu Gurova, T. A. Amashukeli, L. O. Shumlianska, O. A. Kalinichenko, I. A. Kalitova, D. V. Malytsky, V. G. Nikulin, and S. T. Verbytsky. "A study of the properties of the tectonic structure of the Kryvyi Rih city based on statistical analysis of seismicity." Geofizicheskiy Zhurnal 43, no. 6 (February 7, 2022): 248–65. http://dx.doi.org/10.24028/gzh.v43i6.251566.
Анотація:
The article concerns results of studying two significant seismic events — an explosion (23.09.2020 09:00) and an earthquake (30.09.2020 20:00), which occurred in the area of the city of Kryvyi Rih. There were developed algorithms to process records by the Kryvyi Rih seismic station. There was done a comprehensive interpretation of the seismologic and geological-geophysical data. The seismic events’ coordinates were determined, the quality of seismological data processing was evaluated based on the expert method, the level of trustworthiness of the resulting parameters was estimated. The nature of the eathquake’s origin was analyzed based on the shape and the records’. The structure of the mechanism of the earthquake center shows that this was a natural seismic event of the induced type. The article also provides results of geotectonics study of the region of its origin and shows the connection of the geological structures with the epicenter’s parameters. The parameters of the stress-strain state of the crust in the Kryvyi Rih iron-ore basin are calculated, and the parameters of the epicenter of the induced earthquake (2020.09.30 20:00:40.836, UTC) are established. The experimentally calculated depth of the epicenter of local earthquake coincides with the hypothetical depth of 15 km at the lower edge of faults according to the model of the distribution of the depths of the earthquake hypocenters on the Eastern European platform. The proposed methods and algorithms open new opportunities for modern geophysical research in the long-term seismic hazard assessment of Kryvyi Rih. Meanwhile, for a more precise determination of the place, time and nature of local seismic events in the area it is necessary to develop, here and on adjacent territories, a network of seismic stations capable of recording events of comparable and lesser magnitude.
41
Knapp, James H., Camelia C. Knapp, Victor Raileanu, Liviu Matenco, Victor Mocanu, and Cornel Dinu. "Crustal constraints on the origin of mantle seismicity in the Vrancea Zone, Romania: The case for active continental lithospheric delamination." Tectonophysics 410, no. 1-4 (December 2005): 311–23. http://dx.doi.org/10.1016/j.tecto.2005.02.020.
42
Yaghoubi, Ali, SeyedBijan Mahbaz, Maurice B. Dusseault, and Yuri Leonenko. "Seismicity and the State of Stress in the Dezful Embayment, Zagros Fold and Thrust Belt." Geosciences 11, no. 6 (June 12, 2021): 254. http://dx.doi.org/10.3390/geosciences11060254.
Анотація:
This study focuses on determining the orientation and constraining the magnitude of present-day stresses in the Dezful Embayment in Iran’s Zagros Fold and Thrust Belt. Two datasets are used: the first includes petrophysical data from 25 wells (3 to 4 km deep), and the second contains 108 earthquake focal mechanisms, mostly occurring in blind active basement faults (5 to 20 km deep). Formal stress inversion analysis of the focal mechanisms demonstrates that there is currently a compressional stress state (Aφ=2.0–2.2) in the basement. The seismologically determined SHmax direction is 37° ± 10°, nearly perpendicular to the strike of most faults in the region. However, borehole geomechanics analysis using rock strength and drilling evidence leads to the counterintuitive result that the shallow state of stress is a normal/strike-slip regime. These results are consistent with the low seismicity level in the sedimentary cover in the Dezful Embayment, and may be evidence of stress decoupling due to the existence of salt layers. The stress state situation in the field was used to identify the optimally oriented fault planes and the fault friction coefficient. This finding also aligns with the prediction Coulomb faulting theory in that the N-S strike-slip basement Kazerun Fault System has an unfavorable orientation for slip in a reverse fault regime with an average SW-NE SHmax orientation. These results are useful for determining the origin of seismic activity in the basin and better assessing fault-associated seismic hazards in the area.
43
Masci, F., and J. N. Thomas. "Review Article: On the relation between the seismic activity and the Hurst exponent of the geomagnetic field at the time of the 2000 Izu swarm." Natural Hazards and Earth System Sciences 13, no. 9 (September 6, 2013): 2189–94. http://dx.doi.org/10.5194/nhess-13-2189-2013.
Анотація:
Abstract. Many papers document the observation of earthquake-related precursory signatures in geomagnetic field data. However, the significance of these findings is ambiguous because the authors did not adequately take into account that these signals could have been generated by other sources, and the seismogenic origin of these signals have not been validated by comparison with independent datasets. Thus, they are not reliable examples of magnetic disturbances induced by the seismic activity. Hayakawa et al. (2004) claim that at the time of the 2000 Izu swarm the Hurst exponent of the Ultra-Low-Frequency (ULF: 0.001–10 Hz) band of the geomagnetic field varied in accord with the energy released by the seismicity. The present paper demonstrates that the behaviour of the Hurst exponent was insufficiently investigated and also misinterpreted by the authors. We clearly show that during the Izu swarm the changes of the Hurst exponent were strongly related to the level of global geomagnetic activity and not to the increase of the local seismic activity.
44
Masci, F., and J. N. Thomas. "Review "On the relation between the seismic activity and the Hurst exponent of the geomagnetic field at the time of the 2000 Izu swarm"." Natural Hazards and Earth System Sciences Discussions 1, no. 2 (March 26, 2013): 681–91. http://dx.doi.org/10.5194/nhessd-1-681-2013.
Анотація:
Abstract. Many papers document the observation of earthquake-related precursory signatures in geomagnetic field data. However, the significance of these findings is ambiguous because the authors did not adequately take into account that these signals could have been generated by other sources, and the seismogenic origin of these signals have not been validated by comparison with independent datasets. Thus, they are not reliable examples of magnetic disturbances induced by the seismic activity. Hayakawa et al. (2004) claim that at the time of the 2000 Izu swarm the Hurst exponent of the Ultra-Low-Frequency (ULF: 0.001–10 Hz) band of the geomagnetic field varied in accord with the energy released by the seismicity. The present paper demonstrates that the behaviour of the Hurst exponent was insufficiently investigated and also misinterpreted by the authors. We clearly show that during the Izu swarm the changes of the Hurst exponent were strongly related to the level of global geomagnetic activity and not to the increase of the local seismic activity.
45
Scafidi, Davide, Alfio Viganò, Jacopo Boaga, Valeria Cascone, Simone Barani, Daniele Spallarossa, Gabriele Ferretti, Mauro Carli, and Giancarlo De Marchi. "A dense micro-electromechanical system (MEMS)-based seismic network in populated areas: rapid estimation of exposure maps in Trentino (NE Italy)." Natural Hazards and Earth System Sciences 24, no. 4 (April 8, 2024): 1249–60. http://dx.doi.org/10.5194/nhess-24-1249-2024.
Анотація:
Abstract. The micro-electromechanical system (MEMS)-based seismic network of Trentino (NE Italy) consists of 73 low-cost accelerometers installed close to inhabited areas. These sensors have a suitable sensitivity to detect moderate-to-strong earthquakes but are able to record even weaker seismicity. The densely distributed peak ground acceleration values recorded by MEMS and other types of stations are integrated within the existing seismic monitoring procedure in order to automatically obtain a complete set of strong motion parameters a few minutes after the origin time. The exposure of the resident population and critical buildings is estimated by quantifying the different levels of shaking, which is expressed according to the Mercalli–Cancani–Sieberg intensity scale. These types of results, summarized in synthetic portable document format (PDF), can be useful for civil protection purposes to evaluate the state of emergency after a strong earthquake in a timely manner and to choose how and where to activate first aid measures and targeted structural monitoring.
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Pritchard, M. E., T. A. Mather, S. R. McNutt, F. J. Delgado, and K. Reath. "Thoughts on the criteria to determine the origin of volcanic unrest as magmatic or non-magmatic." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2139 (January 7, 2019): 20180008. http://dx.doi.org/10.1098/rsta.2018.0008.
Анотація:
As our ability to detect volcanic unrest improves, we are increasingly confronted with the question of whether the unrest has a magmatic origin (magma on the move) or a non-magmatic origin from a change in the hydrothermal system (fluids that are not magma on the move) or tectonic processes. The cause of unrest has critical implications for the potential eruptive hazard (e.g. used in constructing Bayesian Event Trees), but is frequently the subject of debate, even at well-studied systems. Here, we propose a set of multi-disciplinary observations and numerical models that could be used to evaluate conceptual models about the cause of unrest. These include measurements of gas fluxes and compositions and the isotopic signature of some components (e.g. H 2 , He, C, SO 2 , H 2 O , CH 4 and CO 2 ), the spatial and temporal characteristics of ground deformation, thermal output, seismicity, changes in gravity, and whether there is topographic uplift or subsidence spanning hundreds to thousands of years. In several volcanic systems, both magmatic and non-magmatic unrest is occurring at the same time. While none of these observations or models is diagnostic on its own, we illustrate several examples where they have been used together to make a plausible conceptual model of one or more episodes of unrest and whether eruptions did or did not follow the unrest. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics’.
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Dudkin, F., B. R. Arora, V. Korepanov, O. Leontyeva, and A. K. Sharma. "Application of polarization ellipse technique for analysis of ULF magnetic fields from two distant stations in Koyna-Warna seismoactive region, West India." Natural Hazards and Earth System Sciences 10, no. 7 (July 12, 2010): 1513–22. http://dx.doi.org/10.5194/nhess-10-1513-2010.
Анотація:
Abstract. A new approach is developed to find the source azimuth of the ultra low frequency (ULF) electromagnetic (EM) signals believed to be emanating from well defined seismic zone. The method is test applied on magnetic data procured from the seismoactive region of Koyna-Warna, known for prolonged reservoir triggered seismicity. Extremely low-noise, high-sensitivity LEMI-30 search coil magnetometers were used to measure simultaneously the vector magnetic field in the frequency range 0.001–32 Hz at two stations, the one located within and another ~100 km away from the seismic active zone. During the observation campaign extending from 15 March to 30 June 2006 two earthquakes (EQs) of magnitude (ML>4) occurred, which are searched for the presence of precursory EM signals. Comparison of polarization ellipses (PE) parameters formed by the magnetic field components at the measurement stations, in select frequency bands, allows discrimination of seismo-EM signals from the natural background ULF signals of magnetospheric/ionospheric origin. The magnetic field components corresponding to spectral bands dominated by seismo-EM fields define the PE plane which at any instant contains the source of the EM fields. Intersection lines of such defined PE planes for distant observation stations clutter in to the source region. Approximating the magnetic-dipole configuration for the source, the magnetic field components along the intersection lines suggest that azimuth of the EM source align in the NNW-SSE direction. This direction well coincides with the orientation of nodal plane of normal fault plane mechanism for the two largest EQs recorded during the campaign. More significantly the correspondence of this direction with the tectonic controlled trend in local seismicity, it has been surmised that high pressure fluid flow along the fault that facilitate EQs in the region may also be the source mechanism for EM fields by electrokinetic effect.
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Gorshkov, Alexander I., Olga V. Novikova, Sonya Y. Dimitrova, Lyuba D. Dimova, and Reneta B. Raykova. "Potential Locations of Strong Earthquakes in Bulgaria and the Neighbouring Regions." International Journal of Geophysics 2024 (January 25, 2024): 1–13. http://dx.doi.org/10.1155/2024/8103337.
Анотація:
Information about potential earthquake sources is a key issue for seismic hazard assessment. This study presents the application of a phenomenological approach based on pattern recognition to determine the possible locations of strong earthquakes in the Bulgarian region. The technique assumes the origin of strong earthquakes in morphostructural nodes formed around the intersections of morphostructural lineaments identified by morphostructural zoning. For the territory of the Bulgaria and neighbouring regions, 178 nodes were defined in this work. The CORA-3 pattern recognition algorithm identified 59 seismogenic nodes analysing a set of geophysical and geological node’s characteristics. The identified seismogenic nodes are capable to generate earthquakes with magnitude equal to or greater than 6 and are located at the boundaries between the largest tectonic domains: Rila, Pirin, and Rhodope orogens; the Serbian-Macedonian massif; and in the Stara Planina belt. The set of characteristic features of seismogenic nodes indicates that the vicinity of potential nodes is characterized by a high contrast of neotectonic movements of the Earth’s crust and the presence of deep heterogeneities in the Earth’s crust. About 40% of the recognized nodes are not associated with any earthquakes, while the rest of the recognized seismogenic nodes are characterized by an area with a radius of 25 km where earthquakes are known to occur. Part of these “non active” seismogenic nodes are close to the historical events with magnitudes higher than 5.5 since the magnitude and location of historical events have large uncertainties. Another part of the seismogenic nodes may slightly change the location due to the uncertainties in morphostructural zonation. Other nodes may indicate unknown historical seismicity or paleoearthquakes. Defined M6+ seismogenic nodes can fill the potential gaps in the recorded seismicity on the territory of Bulgaria, thus to improve the seismic hazard assessment of the studied region.
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Riggs, Alan C., W. J. Carr, Peter T. Kolesar, and Ray J. Hoffman. "Tectonic Speleogenesis of Devils Hole, Nevada, and Implications for Hydrogeology and the Development of Long, Continuous Paleoenvironmental Records." Quaternary Research 42, no. 3 (November 1994): 241–54. http://dx.doi.org/10.1006/qres.1994.1075.
Анотація:
AbstractDevils Hole, in southern Nevada, is a surface collapse into a deep, planar, steeply dipping fault-controlled fissure in Cambrian limestone and dolostone. The collapse intersects the water table about 15 m below land surface and the fissure extends at least 130 m deeper. Below water, most of the fissure is lined with a >30-cm-thick layer of dense maxillary calcite that precipitated continuously from groundwater for >500,000 yr. The thick mammillary calcite coat implies a long history of calcite-supersaturated groundwaters, which, combined with the absence of dissolutional morphologies, suggests that Devils Hole was not formed by karst processes. Devils Hole is located in a region of active extension; its tectonic origin is shown by evidence of spreading of its planar opening along a fault and by the orientation of its opening and others nearby, perpendicular to the northwest-southeast minimum principal stress direction of the region. Most Quaternary tectonic activity in the area, including seismicity and Quaternary faults and fractures, occurs on or parallel to northeast-striking structures. The hydrogeologic implications of this primarily structural origin are that fracture networks and caves opened by extensional tectonism can act as groundwater flowpaths functionally similar to those developed by karst processes and that, during active extension, transmissivity can be maintained despite infilling by mineral precipitation. Such extensional environments can provide conditions favorable for accumulation of deposits preserving long, continuous paleoenvironmental records. The precipitates in Devils Hole store chronologies of flow system water-level fluctuations, hydrochemistry, a half-million-yr proxy paleoclimate record, evidence of Devils Hole's tectonic origin, and probably atmospheric circulation.
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Jiménez-Espinosa, Rosario, Pilar Hernández-Puentes, and Juan Jiménez-Millán. "Water–Rock Interaction Processes in Tíscar and Larva Active Faults (Betic Cordillera, SE Spain)." Water 16, no. 6 (March 20, 2024): 897. http://dx.doi.org/10.3390/w16060897.
Анотація:
A hydrochemical and mineral study of groundwaters and damaged rocks from the Tíscar and Larva fault zones (Betic Cordillera, Iberian Peninsula) was carried out in order to (a) describe the physical and chemical properties of the groundwaters; (b) recognize significant locations with deep-origin fluids related to active tectonics; (c) and to describe the water–rock interaction and the neoformation of clay mineral processes and their importance in the seismicity of the faults. A sampling campaign was completed between November 2012 and November 2013, during which data were obtained from 23 different groundwater sites in the fault areas. Two main groups of waters were distinguished: (a) Ca2+-Mg2+-HCO3− facies characterized by poor conductivity and salinity; and (b) saline waters (up to 30 meq/L) rich in Ca2+-Mg2+-SO4-Cl− and with an elevated conductivity (frequently > 1000 μS/cm). In addition, a minor group of saline and warm waters (T > 16.5 °C) was found to be Na+-rich and show moderately high B values (>0.33 ppm), and which mig ht be hosted in aquifers deeper than the two main groups. This group of deep-origin waters is oversaturated in clay minerals and is in equilibrium for Ca-Mg carbonate minerals. X-ray diffraction and scanning and transmission electron microscopy data corroborate the crystallization forecast of authigenic smectite, which appears as thin films coating carbonate fragments. The origin of smectite is related to the fragile strain and thermal–fluid–mineral interactions in fault rocks. Smectite could lubricate carbonate rocks, which favor creep deformation versus seismic slip. This work provides locations where groundwater physico-chemical properties and composition suggest tectonic fault activity.