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Kayal, J. R.
- Seismotectonic Study of the Two Recent SCR Earthquakes in Central India
Authors
1 Geological Survey of India, 27 J.L. Nehru Road, Calcutta - 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 55, No 2 (2000), Pagination: 123-138Abstract
Seismotectonics of the two recent earthquakes, 1993 Killari, mh 6.3 and 1997 Jabalpur, mh 6.0, are examined to understand the nature of seismicity and generating process of the Stable Continental Region (SCR) earthquakes in central India. The Killari earthquake and its aftershocks are confined to a shallower depth (0 - 15 km), a common type of SCR events, whereas the Jabdpur earthquake and its aftershocks occurred at a deeper depth (35-40 km), uncommon in SCR seismicity. The frequency-magnitude relation (b-value) estimated for the two aftershock sequences is compatible (0.46 and 0.49), and is typical for a SCR. The attenuation rates (p-value) of the aftershocks are, however, very much different; it is low (0.27) for the Killari aftershock sequence and high (1.30) for the Jabalpur sequence; the aftershocks continued for about six months in the Killari area, whereas it died down within one and a half months in Jabalpur area for almost a similar magnitude of the main shock. The maximum intensity reached VII for both the main shocks.Fault-plane solutions of the Killari earthquakes reveal reverse faulting for the main shock and the deeper aftershocks (depth 6-15 km) and strike-slip faulting for the shallower aftershocks (0-5 km). It is inferred that interaction of two faults generated the main shock and the aftershocks at shallower depth. These two faults are correlatable with the E-W Tirna river and NW-SE Tirna tributary. The Jabalpur earthquake and its aftershocks, on the other hand, reveal a consistent reverse-fault mechanism with a left-lateral strike-slip motion. The deep ischolar_mained Narmada South Fault has been activated at the crust-mantle boundary and generated the main shock and the aftershocks at deeper depth. The consistent NNE-SSW compressional stress, revealed by the fault-plane solutions, suggests that the SCR earthquakes in Peninsular India are generated by the relative movement of various crustal blocks along pre-existing faults/weak zones at different depth levels due to post collisional movement of the Indian plate in the NNE direction.
Keywords
Seismotectonics, Macroseismic, Microearthquake, Fault-Plane Solution, Isoseist, Madhya Pradesh, Maharashtra.
- Jabalpur Earthquake of May 22, 1997: Constraint from Aftershock Study
Authors
1 Geological Survey of India, 27, J. L. Nehru Road, Calcutta - 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 51, No 3 (1998), Pagination: 295-304Abstract
Macroseismic and microseismic (aftershock) investigations were carried out by the Geological Survey of India immediately after the Jabal pur earthquake (M 6.0) of May 22, 1997. The meizoseismal area of an intensity VIII (MSK) is 35 km long and 15 km wide, trending ENE-WSW. The aftershock investigation was earned out by a five-station temporary microearthquake (MEQ) network. Five felt aftershocks (M≥3.0) and 23 aftershocks in the magnitude range 1.5 to < 3.0 were recorded by the network. These are mostly clustered in an elongated area, 15 ×10 krn, near the main shock epicentre. and occurred at a depth range 35-40 k.m which is compatible with that of the main shock. The fault-plane solution of the main shock and the aftershocks revealed reverse faulting with left-lateral strike-slip component The hypocentral section and the fault-plane solutions indicate that the pre-existing ENE-WSW trending Nannada South Fault is deep-ischolar_mained to mantIe depth, and has been activated at the crust-mantle boundary to produce the main shock and the aftershocks. The failure appears to be caused in response to the northward post collisional movement of the Indian plate.Keywords
Earthquake, Aftershocks. Microseismicity, Fault-Plane Solution, Jabajpur, Madhya Pradesh.- Geophysical and Seismological Investigations for the Hidden Oldham Fault in the Shillong Plateau and Assam Valley of Northeast India
Authors
1 Geological Survey of India, Central Geophysics Division, 27, J.L. Nehru Road, Kolkata - 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No 2 (2007), Pagination: 359-372Abstract
A geophysical field investigation, deploying Magnetotelluric (MT) and Deep Electrical Resistivity Sounding (DES), and analysis of the seismological data were carried out in the Shillong Plateau and Assam Valley area for deciphering the south dipping hidden Oldham fault at the plateau and valley boundary. Bilham and England (2001) reported that the great 1897 Shillong earthquake was caused by the pop-up tectonics of the Shillong Plateau between the two bounding faults, the south dipping hidden Oldham fault to the north and the well known north dipping Dauki fault to the south at the Plateau and Bengal basin boundary. The MT survey was carried out using SAMTEC-2 MT instrument, and the DES was conducted by unilateral equatorial arrays with 5-10 km separation between the transmitting and receiving dipoles. A total of 14 DES and 21 MT soundings were observed in the area. The DES delineated different subsurface layers down to a depth of about 1.5 km. It is observed that the depth of the high resistivity basement (granite gneiss/Archaea.n gneiss) increases towards north of Brahmaputra river; the depth varies from 150111 to 650 rn. To the south of Brahmputra, on the other hand, the depth of the basement is shalIower, it varies from 56m to 340 m. The MT soundings were conducted along three parallel north-south traverses in the area : Traverse I along Dauki-Kaurbaha, from Bangladesh border to Bhutan border, Traverse I1 dong Chherapunjee-Chhagaon and the Traverse I11 along Dainadubi-Dalgama, across the boundary of the ShilIong Plateau and Assam Valley, The traverses I1 and 111 were too shon due to local problems. Interpretation of the 21 MT soundings reveals a conductive horizon at a deeper lcvel (7-8 km) only at the Kulsi (Traverse 11) and at the,Dalgama (Traverse 111) stations, to the north of the proposed Oldham fault. These limited MT observations, however, do not resolve the south dipping hidden Oldham fault.
The seismological data recorded by the permanent network in the Shillong Plateau and Assarn Valley area during the last decade (1990-1997) are analysed. A intense seismic activity is observed in the Plateau region. A north-south depth section of the earthquakes across the Plate'au and the valley, suggests that the most intense seismic activity beneath the Plateau is bounded by two major tectonic features, the north dipping Dapsi thrust, western extension of the Dauki fault, and the south dipping Oldham fault. A detailed gravity survey and a deeper MT survey along longer traverses across the Oldham fault may shed more light on this hidden structure.Keywords
Magnetotelluric, Deep Resistivity, Oldham Fault, Shillong Plateau, Assam Valley.- Geophysical and Seismological Investigations for the Hidden Oldham Fault in the Shillong Plateau and Assam Valley of Northeast India
Authors
1 Geological Survey of India, Op TNPK, Chennai, IN
2 Geological Survey of India, Kolkata, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 1 (2007), Pagination: 172-172Abstract
No Abstract.Full Text
- Indo-US Workshop on Seismicity and Geodynamics
Authors
1 Central Geophysics Division, Geological Survey of India, 27, J L Nehru Road Kolkata 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 63, No 1 (2004), Pagination: 113-114Abstract
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- The March 1999 Chamoli Earthquake in the Garhwal Himalaya: Aftershock Characteristics and Tectonic Structure
Authors
1 Gelogical Survey of India, Central Geophysics Division, 27, J.N. Road, Kolkata - 70001 6, IN
2 Geological Survey of India, Northern Region, Lucknow - 226 024, IN
3 Geological Survey of India, Eastern Region, Salt Lake, Kolkata - 700 094, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 62, No 5 (2003), Pagination: 558-580Abstract
The aftershock sequence of the Chamoli earthquake (mb 6.3) of March 28, 1999 provides an opportunity to study the aftershock characteristics and the seisrnotectonic structure in the Garhwal Himalaya. Detailed analysis of the spatial variation, the frequency-magnitude distribution (b-value), the activity decay-rate (p-value) and fault-plane solutions of the aftershocks throw new light on the aftershock characteristics and seismotectonics of the region. The observations suggest that the aftershock generating process and the b- and p- values changed with time, space and magnitude-ranges. The main shock occurred on the Basement Thrust by a thrust-fault mechanism. The aftershocks, on the other hand, are triggered by the seismogenic faults to the south of the Main Central Thrust (MCT) by thrust as well as by strike-slip faulting, and all the events occurred above the plane of detachment.Keywords
Main shock, Aftershocks, Seismicity, Fault-Plane Solution, Seismotectonics, Chamoli, Garhwal Himalaya.- Mapping the b-Value and its Correlation with the Fractal Dimension in the Northeast Region of India
Authors
1 Geological Survey of India, 27 J.L. Nehru Road, Kolkata - 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 62, No 6 (2003), Pagination: 680-695Abstract
The northeast region of India, one of the most tectonically complex and high seismicity prone regions in the world, is examined with the power law distribution and fractal dimension of seismicity. About 1250 earthquakes (M 2.0 - 5.0) recorded by the permanent stationsltelemetric networks in the region during the period 1993-96 are analysed in this study. The Gutenberg-Richter power law distribution, b-value, is estimated by least square fit and maximum likelihood methods in the five selected tectonic blocks of the region. The b-values (0.5 - 0.9) obtained for the earthquakes (2.5 ≤ M ≤ 5.0) by both the methods are comparable, and it varies with space and depth. The spatial variations of b-value and the activity level ('a' coostant in the power law relation) are mapped. The maps imaged the higher frequency of earthquake occurrence as well as the higher activity level of the seismogenic structures in the region. The fractal dimensions (D) of spatial distribution of earthquakes in the selected tectonic blocks are calculated using the correlation integral. The estimated D values vary from 1.20 to 1.80.Keywords
Seismicity, b-Values, Fractal Dimensions, Northeastern India.- Aftershocks of the 26 January, 2001 Bhuj Earthquake in Western India and its Seismotectonic Implications
Authors
1 Geological Survey of India (GSI), Central Geophysics Division, 27 J.L. Nehru Road, Kolkata - 700 016, IN
2 GSI (ER), Kolkata, IN
3 GSI (NR), Lucknow, IN
4 GSI (CR), Nagpur, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 59, No 5 (2002), Pagination: 395-417Abstract
Fourteen seismographs were deployed by the Geological Survey of India for monitoring aftershocks of the 26 January, 2001 Bhuj earthquake (Mw 7.5) in the Kutch district of Gujarat State, western India. About 3000 aftershocks (M≥ 1.0) were recorded during the period from 29 January to 15 April, 2001. The aftershocks attenuated with time following the power law t-P, where p = 0.91. The frequency-magnitude relation of the aftershocks also followed the power law with b-value = 1.21.About 800 events (M≥ 2.0) are well located with an average RMS ≤ 0.2s and average horizontal and depth error ≤3 km. The epicentre map shows an aftershock-cluster area, about 60 km × 30 km, between 70.0°-70.6° E and 23.3°-23.6° N, which reflects the source area of the main shock and aftershocks at depth. The epicentres show two major trends - in a NE direction and a NW direction. Depth-sections of the aftershocks indicate that the events are mostly generated at 15 to 38 km depth. Some events occurred at depth ≤ 10 km; they follow the NW trend only. A south dipping seismogenic plane is revealed in the depth-sections
.Composite fault-plane solutions of the best-located and selected events are studied. The deeper (25 to 38 km) as well as the mid crustal (15 to <25 km) aftershocks show reverse faulting with a large left-lateral strike-slip component along the NE trending inferred fault, which are comparable with the main-shock solution. Along the NW trending inferred fault, on the other hand, the shallower aftershocks (depth <10 km) show reverse faulting with right-lateral strike-slip component, and the mid crustal and deeper aftershocks show almost pure reverse faulting. These solutions with the NW trending inferred fault are not comparable with the main shock solution. It is inferred that intersection of the two faults has been the source area for stress accumulation to generate the main shock and the aftershocks. The main shock generated rupture propagation by left-lateral strike-slip along the NE trending fault, and by pure reverse to right-lateral strike-slip along the NW trending fault.
Keywords
Aftershocks, Earthquake, Seismotectonics, Seismology, Bhuj, Gujarat.- The Nature of Seismic Sources and the Prediction of Earthquakes
Authors
1 Central Geophysics Division, Geological Survey of India, 27, J.L. Nehru Road, Kolkata - 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 60, No 4 (2002), Pagination: 467-469Abstract
No Abstract.Full Text
- Source Parameters and Focal Mechanisms of Local Earthquakes: Single Broadband Observatory at ISM Dhanbad
Authors
1 Department of Applied Geophysics, Indian School of Mines, Dhanbad - 826 004, IN
2 Department Geology and Geophysics, IIT Kharagpur, Kharagpur - 721 302, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 74, No 3 (2009), Pagination: 413-419Abstract
A three-component broadband seismograph is in operation since January 2007 at the Indian School of Mines (ISM) campus. We have used the broadband seismograms of two local earthquakes M <3 recorded by this single station to illustrate its efficacy in understanding the source processes and tectonics in Dhanbad area. Source parameters and fault plane solutions are obtained through waveform inversion. It is observed that these two earthquakes occurred in the lower crust at a depth of 26 km by strike slip faulting. North-south compressional and east-west tensional stresses are dominant in the area, and the lower crust is the source area for the local earthquakes.Keywords
Earthquake, Broadband, Seismograph, Dhanbad.References
- BAUMBACH, M. and BORMANN, P. (2002) Determination of source parameters from seismic spectra. In: P. Bormann (Ed.), IASPEI manual of Seismological Observatory Practice. GFZ Publication.
- BHATTACHARYA, S.N. (1992) Generation of synthetic seismograms with layer reduction. Geophys. Jour. Internat., v.111, pp.79-90.
- BHATTACHARYA, S.N. and DATTATRAYAM, R.S. (2003) Some Characteristics of Recent Earthquake Sequences in Peninsular India. Gondwana Geol. Magz., v.5, pp.67-85.
- BHATTACHARYA, S.N., GHOSE, A.K., SURESH, G., BAIDYA, P.R. and SAXENA, R.C. (1997) Source parameters of Jabalpur earthquake of 22 May 1997. Curr. Sci., v.73, pp.855-863.
- BHATTACHARYA, S.N., SURESH, G. and MITRA, S. (2009) Lithospheric S-wave velocity structure of the Bastar craton, Indian peninsula from surface-wave phase-velocity measurements. Bull. Seism. Soc. Amer., v.99(4), (in press).
- CHANDRA, U. (1977) Earthquakes of Peninsular India- A seismotectonic study. Bull. Seism. Soc. Amer., v.67, pp.1387-1413.
- DREGER, D.S. and HELMBERGER, H.M. (1993) Determination of source parameters at regional distances with three-component sparse network data. Jour. Geophys. Res., v.98, pp.8107-8125..
- GUPTA, H.K. (2002) A review of recent studies of triggered earthquakes by artificial water reservoirs with special emphasis on earthquakes in Koyna, India. Earth Sci. Rev., v.58, pp.279-310.
- KANAMORI, H., MORIM, J. and HEATON, T.H. (1990) The 3 December 1988, Pasadena earthquake (ML = 4.9) recorded with very broadband system in Pasadena. Bull. Seism. Soc. Am., v.80, pp.483-4
- KAYAL, J.R. (2000) Seismotectonic study of the two recent SCR earthquakes in central India. Jour. Geol. Soc. India, v.55, pp.123-138.
- KAYAL, J.R. (2007) Recent large Earthquakes in India: Seismotectonic Perspective. IAGR Mem., no.10, pp.1-11.
- KAYAL, J. R., DE, R., SAGINA RAM, SRIRAMA, B.V. and GAONKAR, S.G. (2002) Aftershocks of the 26 January, 2001 Bhuj earthquake in western India and its seismotectonic implications. Jour. Geol. Soc. India, v.59, pp.395-417.
- KAYAL, J.R., AREFIEV, S.S., BARUAH, S., HAZARIKA, D., GOGOI, N., KUMAR, A., CHOWDHURY, S.N. and KALITA, S. (2006) Shillong Plateau earthquakes in northeast India region: Complex tectonic model. Curr. Sci., v.91(1), pp.109-114.
- KAYAL, J.R., SRIVASTAVA V.K. and KUMAR, PRAKASH (2009) Crustal discontinuities below the ISM Dhanbad Observatory: Receiver function analysis of the teleseismic events (in prep.).
- PINAR, A., KUGE, K. and HONKURA, Y. (2003) Moment-tensor inversion of recent small to moderate sized earthquakes: Implications for seismic hazard and active tectonics beneath the sea of Marmara, Geophys. Jour. Int., v.153, pp.133-145.
- RICHTER, C.F. (1958) Elementary Seismology (Appendix XII), W.H. Freeman, San Francisco.
- SHEARER, P.M. (1999) Introduction to Seismology, Cambridge University Press, 260p.
- WANG, R. (1999) A simple ortho-normalization method for stable and efficient computation of Green's function. Bull. Seism. Soc. Am., v.89, pp.733-741.
- ZAHRADNIK, J., JANSKY, J. and PLICKA, V. (2008) Detailed wave form inversion for moment tensor of M ~ 4 events: Examples from the Corinth Gulf, Greece. Bull. Seism. Soc. Am., v.98, No.6, pp.2756-2771.
- Evaluation of Crustal and Upper Mantle Structures Using Receiver Function Analysis: ISM Broadband Observatory Data
Authors
1 Department of Applied Geophysics, Indian School of Mines, Dhanbad - 826 004, IN
2 National Geophysical Research Institute (Council of Scientific and Industrial Research), Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 78, No 1 (2011), Pagination: 76-80Abstract
A three-component broadband seismograph is in operation since January 2007 at the Indian School of Mines (ISM) campus, Dhanbad. We have used the broadband (BB) seismograms of 17 teleseismic events (M ≥ 5.8) recorded by this single BB station during 2008-09 to estimate the crust and upper mantle discontinuities in Dhanbad area which falls in the peninsular India shield. The converted wave technique and the Receiver function analysis are used. A 1-D velocity model has been derived using inversion. The Mohorovicic (Moho) discontinuity (crustal thickness) below the ISM observatory is estimated to be ~41 km, with an average Poisson ratio of ~0.28, suggesting that the crust below the Dhanbad area is intermediate to mafic in nature. The single station BB data shed new light to the estimate of crustal thickness beneath the eastern India shield area, which was hitherto elusive. Further, it is observed that the global upper mantle discontinuity at 410 km is delayed by ~0.6 sec compared to the IASP-91 global model; this may be explained by a slower/hotter upper mantle; while the 660 km discontinuity is within the noise level of data.Keywords
Broadband Seismograms, Teleseismic Events, Receiver Function, Crust and Upper Mantle, Moho Discontinuity.- Research Highlights in Earth System Science
Authors
1 Central Geophysics Division, Geological Survey of India, Kolkata - 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 60, No 5 (2002), Pagination: 609-610Abstract
No Abstract.Full Text