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Stress triggering of normal aftershocks due to strike slip earthquakes in compressive regime 总被引：2，自引：0，他引：2
A few cases of occurrence of normal aftershocks after strike slip earthquakes in compressive regime have been reported in the literature. Occurrence of such aftershocks is intriguing as they occurred despite the apparent stabilizing influence of compressive plate tectonic stresses on the normal faults. To investigate the occurrence processes of such earthquakes, we calculate change in static stress on optimally oriented normal and reverse faults in the dilational and compressional step over zones, respectively, due to slip on a vertical strike slip fault under compressive regime. We find that change in static stress is much more pronounced on normal faults as compared to that on reverse faults, for all values of fault friction. Change in static stress on reverse fault is marginally positive only when the fault friction is low, whereas for normal faults it is positive for all values of fault friction, and is maximum for high fault friction. We suggest that strike slip faulting in compressive regime creates a localized tensile environment in the dilational step over zone, which causes normal faulting in that region. The aftershocks on such normal faults are considered to have occurred as an almost instantaneous response of stress transfer due to strike slip motion. 相似文献
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We analyse aftershocks of the 26 January 2001 Bhuj earthquake, India, that were recorded for 10 weeks following the mainshock. We calculate undrained or instantaneous pore pressure and change in Coulomb stress due to the earthquake and their poroelastic relaxation in the following 10 weeks period. Almost all aftershocks occurred in the region of coseismic dilatation. In the subsequent period, pore pressure increased through relaxation in the dilatation region which further modified coseismic Coulomb stress. Maximum increase in pore pressure is estimated to be about 0.7 MPa in 60 days time following the mainshock. Correlation between the zones of increased pore pressure and postseismic Coulomb stress with that of aftershocks, suggests a definite role of fluid diffusion in their delayed triggering. 相似文献
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Koyna-Warna region in western India is a globally recognized site of reservoir-triggered seismicity near the Koyna and Warna reservoirs. The region has been reported with several M?>?5 earthquakes in the last five decades including M6.3 Koyna earthquake which is considered as the largest triggered earthquake worldwide. In the present study, a detailed statistical analysis has been done for long period earthquake catalogues during 1968–2004 of MERI and 2005–2012 of CSIR-NGRI to find out the spatio-temporal influence of the Koyna and Warna reservoirs impoundment on the seismicity of the region. Depending upon the earthquake clusters, we divided the region into three different zones and performed power spectrum and singular spectrum analysis (SSA) on them. For the time period 1983–1995, the earthquake zone near the Warna reservoir; for 1996–2004, the earthquake zone near the Koyna reservoir; and for 2005–2012, the earthquake zone near the Warna reservoir found to be influenced by the annual water level variations in the reservoirs that confirm the continuous role of both the reservoirs in the seismicity of the Koyna-Warna region. 相似文献
4.
The Muzaffarabad region in western Himalaya, the site of the devastating earthquake of 8 October 2005 of magnitude 7.6, occupies
a unique tectonic position, encompassed by the Himalayan arc to the east and the complex thrust zones of Pamir and Hindukush
in the north and northwest respectively. Further, the region is entangled in a peculiar overturned syntaxial bend of the Main
Central Thrust (MCT), north of Main Boundary Thrust (MBT). A study of focal mechanisms and stress inversion in each of these
regions indicates varied stress regimes demonstrating their distinct tectonic character. While shallow plane thrust faulting
with low dip angles is generally witnessed along the Himalayan arc, a transition to steep fault plane dips up to 45° is seen
in the Muzaffarabad region on the western side. It is inferred that the stress field in Muzaffarabad region is not a mere
extension of that in the Himalayan arc but is controlled by the complex interplay of the surrounding diverse tectonic structural
units comprising the Himalaya, Hindukush and Pamir, rather than merely the tectonic forces of India–Eurasia collision. 相似文献
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Limited reports of repeat triangulation and levelling surveys carried out in the Koyna region by Survey of India, before and after the 1967 Koyna earthquake, are available. We analyse these observations of horizontal and vertical displacements to investigate whether analysis of these observations can provide additional constraints on the source parameters of the 1967 Koyna earthquake. We calculate surface displacements due to coseismic slip on the subsurface rupture of the 1967 Koyna earthquake and also due to the Koyna reservoir water load. We find that the reported displacements are too large to be attributed to the coseismic displacements and/or to the displacements induced by the reservoir water load. We conclude that these observations contain large random and systematic errors. 相似文献
6.
Pallabee Choudhury Kalpna Gahalaut Rakesh Dumka V. K. Gahalaut Abhay Kumar Singh Sanjay Kumar 《Environmental Earth Sciences》2018,77(22):770
A continuous GPS measurement site, ISRR, at Gandhinagar (Western India), documented ~?5 mm/year of surface subsidence rate during 2009–2016. Preliminary modelling using an analytical solution indicates that the observed surface subsidence rate at the ISRR site is consistent with the ground water depletion reported from Gandhinagar. An assessment of data from GPS sites at Lucknow and Varanasi in the Indo-Gangetic plains in Northern India does not indicate any significant subsidence at these sites which is also consistent with the in situ observations of insignificant depletion of ground water in the region. 相似文献
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The Killari earthquake of September 29, 1993 (Mw=6.2) in peninsular India triggered several aftershocks that were recorded by a network of 21 stations. We computed the change in regional static stress caused by coseismic slip on the earthquake rupture and correlated it with the aftershocks with a view to constrain some of the rupture parameters of this earthquake. We evaluated the six available estimates of fault plane solutions for this earthquake and concluded that reverse slip on a 42° dipping, N112° trending fault, which extends up to the surface from a depth of 7 km, produces maximum correlation between the increased static stress and aftershock distribution. Our analysis suggests that the majority of coseismic slip occurred on the part of the rupture that lies in the depth range of 3–6.5 km. 相似文献
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Earthquakes in Koyna-Warna region are triggered by the reservoirs but the reasons for sustained seismicity, in terms of magnitude and time, remain enigmatic. We critically review the proposed models/processes, which include fault interaction, flexure of Western Ghat escarpment, velocity heterogeneity, and earthquakes being considered as aftershocks. We suggest that each of these processes or models have limitations and are not capable of explaining all the features of seismicity individually. It is possible that all put together and some other unknown additional processes are at work and there is a mish-mash of several processes attending the region, causing continuing seismicity for past five decades. 相似文献
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A new case of reservoir triggered seismicity: Govind Ballav Pant reservoir (Rihand dam), central India 总被引：2，自引：0，他引：2
We report here that seismicity near Govind Ballav Pant reservoir is strongly influenced by the reservoir operations. It is the second largest reservoir in India, which is built on Rihand river in the failed rift region of central India. Most of the earthquakes occurred during the high water stand in the reservoir with a time lag of about 1 month. We use the concept of coulomb stress change and use Green's function based approach to estimate stresses and pore pressure due to the reservoir load. We find that the reservoir increases coulomb stress on the nearby faults of the region that are favourably oriented for failure in predominantly reverse slip manner under the NNE–SSW compression and thus promotes failure. The above two factors make it an obvious, yet so far unreported case of reservoir triggered seismicity. 相似文献
10.
Thai Anh Tuan N. Purnachandra Rao Kalpna Gahalaut Cao Dinh Trong Le Van Dung Cao Chien K. Mallika 《Journal of Seismology》2017,21(5):1131-1143
In the Song Tranh 2 (ST2) hydropower reservoir located in the Quang Nam province, Central Vietnam, earthquakes started occurring soon after impoundment of the reservoir in late 2010. Earthquakes continue to occur in the region, and two earthquakes of M 4.6 and 4.7 on October 22, 2012 and November 15, 2012, respectively, have been reported (Trieu et al. 2014; Giang et al. 2015) in the vicinity of the reservoir. In the present study, b-value has been estimated, and focal mechanism solutions have been computed for the first time using moment tensor inversion approach. Also, the influence of impoundment of reservoir on the occurrence of earthquakes has been computed for the ST2 region based on Coulomb stress. A quality data set of 595 earthquakes recorded for the period of October 2012 to April 2014 at ten stations of the seismic network operated by the Institute of Geophysics (IGP) has been used to calculate b-values for the northern and southern seismicity clusters of the region. In general, the b-values associated with reservoir-triggered seismicity (RTS) are found to be higher than the regional b-values in the frequency-magnitude relation of earthquakes. For the ST2 region, it is found that the b-values for the northern and southern clusters are 0.94 ± 0.04 and 0.90 ± 0.04, respectively. Focal mechanism solutions obtained for the two earthquakes close to the reservoir have a right-lateral strike-slip mechanism, with the preferred planes trending NW-SE. These results are concurrent with the orientation of the nearby local surface faults, which we confirm as the active faults in this region. Influence of the stresses due to reservoir water load on the local seismicity is computed based on the obtained focal mechanism by using the concept of fault stability. It is found that most of the earthquakes occur in the positive Coulomb stress region, which shows the influence of reservoir impoundment on earthquake occurrence in the vicinity. Our results suggest that the local earthquakes are triggered by the impoundment of the ST2 reservoir. 相似文献
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