Seismicity and the state of stress from investigations of local earthquakes in the Kumaon Himalaya

Gaur, V. K.; Chander, Ramesh; Sarkar, Irene; Khattri, K. N.; Sinvhal, H.

doi:10.1016/0040-1951(85)90123-4

Cited by 46 publications

(14 citation statements)

References 5 publications

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“…The fault plane solutions of the Himalayan earthquakes predominantly indicate thrust mechanism (Ni and Barazangi 1984;Chandra 1992). However, some normal faults (Singh et al 1977;Khattri et al 1978) and strike-slip mechanism (Das Gupta et al 1982;Gaur et al 1985;Khattri et al 1989;Kumar andMahajan 1991, 2001;Srivastava and Mitra 1994;Power et al 1998;Kayal 2007) have also been reported for the same region. The normal fault and strike-slip mechanism are not typical of the Himalayan earthquakes.…”

Section: Delineation Of Source Zonesmentioning

confidence: 87%

Probabilistic seismic hazard map of NW Himalaya and its adjoining area, India

et al. 2009

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The seismically active Northwest (NW) Himalaya falls within Seismic Zone IV and V of the hazard zonation map of India. The region has suffered several moderate (*25), large-to-great earthquakes (*4) since Assam earthquake of 1897. In view of the major advancement made in understanding the seismicity and seismotectonics of this region during the last two decades, an updated probabilistic seismic hazard map of NW Himalaya and its adjoining areas covering 28-34°N and 74-82°E is prepared. The northwest Himalaya and its adjoining area is divided into nineteen different seismogenic source zones; and two different region-specific attenuation relationships have been used for seismic hazard assessment. The peak ground acceleration (PGA) estimated for 10% probability of exceedance in 50 and 10 years at locations defined in the grid of 0.25 9 0.25°. The computed seismic hazard map reveals longitudinal variation in hazard level along the NW Himalayan arc. The high hazard potential zones are centred around Kashmir region (0.70 g/0.35 g), Kangra region (0.50 g/0.020 g), Kaurik-Spitti region (0.45 g/0.20 g), Garhwal region (0.50 g/0.20 g) and Darchula region (0.50 g/0.20 g) with intervening low hazard area of the order of 0.25 g/0.02 g for 10% probability in 50 and 10 years in each region respectively.

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Section: Delineation Of Source Zonesmentioning

confidence: 87%

Probabilistic seismic hazard map of NW Himalaya and its adjoining area, India

et al. 2009

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“…Although 21 earthquakes (M > 5.5) have occurred in the last one hundred years in Garhwal Himalayas but according to energy budget (Bilham, 2001) a major earthquake is yet to strike in this region and hence it is important to study the seismic activity here specifically to search the evidences for a major probable earthquake in future. The epicentral locations of earthquakes show the existence of a seismic belt that runs almost parallel to the surface trace of MCT and lies between the Alaknanda and Yamuna river valleys (Gaur et al, 1985;Khattri et al, 1989). Other studies based on microearthquakes by Paul et al (2004) and Sharma and Wason (1994) reveal shallow focus events having low values of stress drop.…”

Section: Introductionmentioning

confidence: 92%

Recent earthquake swarms in Garhwal Himalaya: A precursor to moderate to great earthquakes in the region

Paul¹,

Sharma²

2011

Journal of Asian Earth Sciences

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“…Several studies have been carried out to explain the mechanics of these thrust earthquakes, in terms of plate tectonic forces which revealed that the regional plate tectonic lithospheric compressive stresses resulting from the northward movement of the Indian plate were the prime factor in generating interplate seismicity in this region (FITCH, 1970;CHANDRA, 1978;NI and BARAZANGI, 1984;BURCHFIEL and ROYDEN, 1985). A region 200 km long, 100 km wide and about 20 km thick, based on local earthquake hypocentral parameters, has been identi®ed as the Garhwal Himalayan seismic zone (GAUR et al, 1985;KHATTRI et al, 1989). To date, ®ve earthquakes of M6 (including the 1803 Upper Ganga earthquake of intensity IX), twelve earthquakes of magnitude exceeding 5 and several earthquakes of magnitude £5.0 have occurred in the Garhwal Himalayan region (Fig.…”

Section: Tectonic Setupmentioning

confidence: 99%

“…In the last two decades, small earthquakes of Garhwal Himalaya occurred in a narrow belt coinciding with the Himalayan seismic belt. However, GAUR et al (1985) reported, based on the composite focal mechanism solution of selected local earthquakes of the Garhwal Himalaya which occurred at depths less than 10 km below the mean sea level (MSL), that strike-slip faulting can also occur in the region. These earthquakes have been explained in terms of reactivation of upper crustal faults, which are possibly slip surfaces of crustal shear zones facilitating the upliftment of lesser as well as higher Himalaya, and are a consequence of the same underthrusting Himalayan orogenic process prevalent in the entire region.…”

Section: Tectonic Setupmentioning

confidence: 99%

Aftershock Activity and Frequency-dependent Low Coda Qc in the Epicentral Region of the 1999 Chamoli Earthquake of Mw 6.4

Mandal¹,

Padhy²,

Rastogi³

et al. 2001

Pure appl. geophys.

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Ð On 28 March, 1999 (19:05:10.09, UT) a signi®cant earthquake of M w 6.4 occurred in the Garhwal Himalaya (30.555°N, 79.424°E). One hundred and ten well-recorded aftershocks show a WNW-ESE trending northeasterly dipping seismic zone extending from a depth of 2 to 20 km. As the main shock hypocenter occurred at the northern end of this seismic zone and aftershocks extended updip, it is inferred that the main-shock rupture nucleated on the detachment plane at a depth of 15 km and then propagated updip along a NE-dipping thrust plane. Further, the epicentral distribution of aftershocks de®nes a marked concentration near a zone where main central thrust (MCT) takes a signi®cant turn towards the north, which might be acting as an asperity in response to the NNE compression due to the underthrusting of Himalayan orogenic process prevalent in the entire region. Presence of high seismicity including ®ve earthquakes of magnitude exceeding 6 and twelve earthquakes of magnitude exceeding 5 in the 20th century is presumed to have caused a higher level of shallow crustal heterogeneity in the Garhwal Himalaya, a site lying in the central gap zone of the Himalayan frontal arc. Attenuation property of the medium around the epicentral area of the 1999 Chamoli earthquake, covering a circular area of 61,500 km 2 with a radius of 140 km, is studied by estimating the coda Q c from 48 local earthquakes of magnitudes varying from 2.5±4.8. These earthquakes were recorded at nine 24-bit REFTEK digital stations; two of which were equipped with three-component CMG40T broadband seismometers and others with three-component L4-3D short-period seismometers. The estimated Q o values at dierent stations suggest on average a low value of the order of (30 0.8), indicating an attenuating crust beneath the entire region. The frequency-dependent relation indicates a relatively low Q c at lower frequencies (1±3 Hz) that can be attributed to the loss of energy due to scattering on heterogeneities and/or the presence of faults and cracks. The large Q c at higher frequencies may be related to the propagation of backscattered body waves through deeper parts of the lithosphere where less heterogeneities are expected. An important observation is that the region north of MCT (more rigid highly metamorphosed crystalline rocks) is less attenuative in comparison to the region south of MCT (less rigid slightly metamorphosed rocks (sedimentary wedge)). The acceleration decays to 50% at 20 km distance and to 7% at 100 km. Hence, even 1g acceleration at the source may not cause signi®cant damage beyond 100 km in this region.

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Seismicity and the state of stress from investigations of local earthquakes in the Kumaon Himalaya

Cited by 46 publications

References 5 publications

Probabilistic seismic hazard map of NW Himalaya and its adjoining area, India

Probabilistic seismic hazard map of NW Himalaya and its adjoining area, India

Recent earthquake swarms in Garhwal Himalaya: A precursor to moderate to great earthquakes in the region

Aftershock Activity and Frequency-dependent Low Coda Qc in the Epicentral Region of the 1999 Chamoli Earthquake of Mw 6.4

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