Bulletin of the Seismological Society of America, 2011
The lithospheric velocity structure of the lower Indus basin has been evaluated through inversion... more The lithospheric velocity structure of the lower Indus basin has been evaluated through inversion of fundamental modes of both Love and Rayleigh wave group velocities from the broadband records of a seismic network maintained by the Institute of Seismological Research, Gujarat, India. We have considered three clusters of wave paths A, B, and C that mainly cross the lower Indus basin from south to north; the wave paths of A mainly cross the continental shelf, and the wave paths of B and C pass through the lower Indus basin. The measured group velocities correspond to periods of 5 to 90 s for Rayleigh waves, and 5 to 115 s for Love waves. These data sets resolve the structure of the lithosphere through a nonlinear inversion based on a genetic algorithm with a wide solution space. The mean and standard deviation (S.D.) of the 70 accepted solutions for each of these three clusters provide the 2D structure for the lower Indus basin from south to north. The sediment consists of two layers with total thickness from 5.7 to 6.6 km increasing northward. The crustal thickness also increases northward from 32.9 (cluster A) to 39.7 km (cluster C) in the lower Indus region. The S-wave velocity below the crust varies from 4.55 to 4:59 km=s, which is close to the corresponding velocity of 4:60 km=s of the Indian shield region to the east of the Aravalli range. The thicknesses of the lithosphere, as well as the velocities of the uppermost mantle of the lower Indus plain, are similar to that of the Indian shield.
In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysi... more In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysis of surface waves (MASW) method at ten representative sites in the NCT region, New Delhi. The analysis shows that the Vs obtained from the sites located on Alwar quartzites of Delhi Super Group ranges from 770 m/s to 2800 m/s, whereas on other sites located on lake/river sediments (Nazafgarh, Balsava and Akshar Dham) have Vs less than 180 m/s. The sites located on thick sediments shows Vs of the order of 180 m/s to 250 m/s. According to the soil classification, the sites covered can be classified under three categories: Class 'B' (Vs 30 as >760m/s; JNU site and Asola site), class 'D' (Vs 30 >180 m/sec-360; Bhavana, Suhalpur, Ghazipur and Kirbi cantt. sites), whereas the sites located near lake/river sediments are classified as class 'E' (with very soft soil) and will be prone to liquefaction potential during strong earthquake shaking.
International Journal of Geotechnical Earthquake Engineering, 2011
In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysi... more In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysis of surface waves (MASW) method at ten representative sites in the NCT region, New Delhi. The analysis shows that the Vs obtained from the sites located on Alwar quartzites of Delhi Super Group ranges from 770 m/s to 2800 m/s, whereas on other sites located on lake/river sediments (Nazafgarh, Balsava and Akshar Dham) have Vs less than 180 m/s. The sites located on thick sediments shows Vs of the order of 180 m/s to 250 m/s. According to the soil classification, the sites covered can be classified under three categories: Class ‘B’ (Vs30 as >760m/s; JNU site and Asola site), class ‘D’ (Vs30>180 m/sec-360; Bhavana, Suhalpur, Ghazipur and Kirbi cantt. sites), whereas the sites located near lake/river sediments are classified as class ‘E’ (with very soft soil) and will be prone to liquefaction potential during strong earthquake shaking.
Abstract The lithospheric velocity structure of the lower Indus basin has been evaluated through ... more Abstract The lithospheric velocity structure of the lower Indus basin has been evaluated through inversion of fundamental modes of both Love and Rayleigh wave group velocities from the broadband records of a seismic network maintained by the Institute of ...
The seismically active Northwest (NW) Himalaya falls within Seismic Zone IV and V of the hazard z... more 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 × 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.
Bulletin of the Seismological Society of America, 2011
The lithospheric velocity structure of the lower Indus basin has been evaluated through inversion... more The lithospheric velocity structure of the lower Indus basin has been evaluated through inversion of fundamental modes of both Love and Rayleigh wave group velocities from the broadband records of a seismic network maintained by the Institute of Seismological Research, Gujarat, India. We have considered three clusters of wave paths A, B, and C that mainly cross the lower Indus basin from south to north; the wave paths of A mainly cross the continental shelf, and the wave paths of B and C pass through the lower Indus basin. The measured group velocities correspond to periods of 5 to 90 s for Rayleigh waves, and 5 to 115 s for Love waves. These data sets resolve the structure of the lithosphere through a nonlinear inversion based on a genetic algorithm with a wide solution space. The mean and standard deviation (S.D.) of the 70 accepted solutions for each of these three clusters provide the 2D structure for the lower Indus basin from south to north. The sediment consists of two layers with total thickness from 5.7 to 6.6 km increasing northward. The crustal thickness also increases northward from 32.9 (cluster A) to 39.7 km (cluster C) in the lower Indus region. The S-wave velocity below the crust varies from 4.55 to 4:59 km=s, which is close to the corresponding velocity of 4:60 km=s of the Indian shield region to the east of the Aravalli range. The thicknesses of the lithosphere, as well as the velocities of the uppermost mantle of the lower Indus plain, are similar to that of the Indian shield.
In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysi... more In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysis of surface waves (MASW) method at ten representative sites in the NCT region, New Delhi. The analysis shows that the Vs obtained from the sites located on Alwar quartzites of Delhi Super Group ranges from 770 m/s to 2800 m/s, whereas on other sites located on lake/river sediments (Nazafgarh, Balsava and Akshar Dham) have Vs less than 180 m/s. The sites located on thick sediments shows Vs of the order of 180 m/s to 250 m/s. According to the soil classification, the sites covered can be classified under three categories: Class 'B' (Vs 30 as >760m/s; JNU site and Asola site), class 'D' (Vs 30 >180 m/sec-360; Bhavana, Suhalpur, Ghazipur and Kirbi cantt. sites), whereas the sites located near lake/river sediments are classified as class 'E' (with very soft soil) and will be prone to liquefaction potential during strong earthquake shaking.
International Journal of Geotechnical Earthquake Engineering, 2011
In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysi... more In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysis of surface waves (MASW) method at ten representative sites in the NCT region, New Delhi. The analysis shows that the Vs obtained from the sites located on Alwar quartzites of Delhi Super Group ranges from 770 m/s to 2800 m/s, whereas on other sites located on lake/river sediments (Nazafgarh, Balsava and Akshar Dham) have Vs less than 180 m/s. The sites located on thick sediments shows Vs of the order of 180 m/s to 250 m/s. According to the soil classification, the sites covered can be classified under three categories: Class ‘B’ (Vs30 as >760m/s; JNU site and Asola site), class ‘D’ (Vs30>180 m/sec-360; Bhavana, Suhalpur, Ghazipur and Kirbi cantt. sites), whereas the sites located near lake/river sediments are classified as class ‘E’ (with very soft soil) and will be prone to liquefaction potential during strong earthquake shaking.
Abstract The lithospheric velocity structure of the lower Indus basin has been evaluated through ... more Abstract The lithospheric velocity structure of the lower Indus basin has been evaluated through inversion of fundamental modes of both Love and Rayleigh wave group velocities from the broadband records of a seismic network maintained by the Institute of ...
The seismically active Northwest (NW) Himalaya falls within Seismic Zone IV and V of the hazard z... more 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 × 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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