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Papers by DD Singh

Research paper thumbnail of Anelasticity of the crust and upper mantle beneath the Eurasian continent and the nearby regions from the inversion of Love and Rayleigh wave attenuation data

Geophysical Journal International, 1982

The fundamental mode Love and Rayleigh waves generated by five earthquakes, which occurred in cen... more The fundamental mode Love and Rayleigh waves generated by five earthquakes, which occurred in central Asia and were recorded at 20-35 WWSSN stations throughout the world, are analysed. The Love and Rayleigh wave attenuations are determined at the time period of 10-120s for the continental and oceanic paths across Eurasia and nearby regions using the spectral amplitudes of these waves. The large standard deviation observed in the attenuation coefficients of surface waves may be due to the regional variation of the attenuative properties of the crust and upper mantle beneath Eurasia. The continental Rayleigh wave attenuation coefficients are smaller by a factor of up to 2 compared to oceanic paths. The continental Rayleigh wave attenuation coefficient attains two minima of 0.1 5 x and 0.1 1 x 10-3km-1 at the time periods of 3 5 and 80 s respectively, and two maxima of 0. 5 8~ and 0.3 x 10-3km-' at time periods of 10 and 100s respectively. A similar trend is observed for the oceanic paths as well. Backus and Gilbert inversion theory is applied to these Love and Rayleigh waves attenuation data to obtain Qj' models for the crust and upper mantle beneath Eurasia and the nearby regions. Independent inversion of continental Love and Rayleigh waves attenuation data yields the thickness of the lithosphere to be 90 km. For the oceanic paths, the thickness of the lithosphere is estimated t o be 110 km. The base of the lithosphere is identified as the depth at which QF' increases sharply. Qj' in the asthenosphere is greater to a minimum of a factor of 2 as compared to the lithosphere.

Research paper thumbnail of Surface-wave radiation pattern and source parameters of Koyna earthquake of December 10, 1967

Bulletin of the Seismological Society of America, Jun 1, 1975

Page 1. Bulletin ot the Seismological Society of America. Vol. 65, No. 3; pp. 711-731. June 1975 ... more Page 1. Bulletin ot the Seismological Society of America. Vol. 65, No. 3; pp. 711-731. June 1975 SURFACE-WAVE RADIATION PATTERN AND SOURCE PARAMETERS OF KOYNA EARTHQUAKE OF DECEMBER 10, 1967 ...

Research paper thumbnail of Determination of upper mantle velocity structure using the P and S waves spectra

Annals of Geophysics, 2010

Research paper thumbnail of Quasi-continental oceanic structure beneath the Arabian Fan sediments from observed surface-wave dispersion studies

Bulletin of the Seismological Society of America, 1988

The fundamental and higher modes of surface waves generated by 31 earthquakes and recorded at sei... more The fundamental and higher modes of surface waves generated by 31 earthquakes and recorded at seismographic stations along the western margins of India and Pakistan (Trivandrum, Kodaikanal, Goa, Bombay, Poona, New Delhi, Nillore, and Quetta) are used to estimate the crustal structure beneath the Arabian Fan sediments. The sedimentary thickness is determined from the observed higher mode data. The observed dispersion data suggest an increase in crustal thickness northward, from an approximately 16 km crustal thickness at the southern tip of India (Trivandrum) to an approximately 28 km crustal thickness at the regions of 20°N and above latitude, with an overlying 6 km sedimentary thickness. This gradual increase in crustal thickness in the northward direction and the attaining of quasi-continental oceanic (transition from continent to ocean) structure beneath the Arabian Fan sediments suggest that the Mohorovičić discontinuity may have resulted from a change in crystal structure due t...

Research paper thumbnail of Source parameters of the Burma-India border earthquake of July 29, 1970, from body waves

Tectonophysics, 1978

Abstract The source parameters are determined for the Burma-India border earthquake of July 29, 1... more Abstract The source parameters are determined for the Burma-India border earthquake of July 29, 1970, from body-wave spectra. We obtain seismic moment [ M o (P) = 4.83 , M o (S) = 3.40 ] · 1026 dyne cm, source dimension [ r (P) = 22.5, −r (S) = 27.7 ] km, radiated energy [ E R (P) = 7.19 , −ER (S) = 1.35] · 1020 ergs and the stress drop = 11 bars.

Research paper thumbnail of Crust and upper-mantle velocity structure beneath the northern and central Indian Ocean from the phase and group velocity of Rayleigh and Love waves

Physics of the Earth and Planetary Interiors, 1988

Research paper thumbnail of Spectral analysis of body waves for earthquakes and their source parameters in the Himalaya and nearby regions

Physics of the Earth and Planetary Interiors, 1979

Research paper thumbnail of Q-structure beneath the Tibetan Plateau from the inversion of Love- and Rayleigh-wave attenuation data

Physics of the Earth and Planetary Interiors, 1982

Research paper thumbnail of Seismotectonics of the Himalaya and its vicinity from centroid-moment tensor (CMT) solution of earthquakes

Journal of Geodynamics, 2000

Research paper thumbnail of Shear-wave velocity and attenuation structure beneath Antarctica determined from surface waves

Geophysical Journal International, 1994

Research paper thumbnail of Transitional continental-oceanic structure beneath the Norwegian Sea from inversion of surface wave group velocity data

Geophysical Journal International, 1999

Research paper thumbnail of Rayleigh-Wave Group-Velocity Studies beneath the Indian Ocean

Bulletin of the Seismological Society of America, 2005

The fundamental mode Rayleigh wave generated by 16 earthquakes, which occurred in the Indian Ocea... more The fundamental mode Rayleigh wave generated by 16 earthquakes, which occurred in the Indian Ocean and were recorded at 14 seismic stations of Asia, Africa, and Australia, are analyzed to estimate the Rayleigh-wave group velocity at periods of 10 to 60 sec by using the multiple filter analysis technique. In addition to this, Rayleigh-wave group-velocity data available in the literature across different propagation paths of the Indian Ocean forming a dense distribution of seismic wave traverses have been considered for tomographic studies. The group-velocity distribution maps have been obtained at periods of 10, 20, 30, 40, 50, and 60 sec for the Rayleigh wave. The minimum value of the group velocity of 2.0 km/sec is centered near the Rodriguez triple junction (25° S, 70° E) at 10 sec and higher value (3.4–4.0 km/sec) at 20 sec and greater period. As we move in the north-northwest direction from the Rodriguez triple junction, the Rayleigh-wave group-velocity isolines at 10 and 20 sec are also increasing in the northern direction in both the east and west sides of the ridge axis. Another minimum value of group-velocity isolines (1.9 km/sec) is centered near (25° S, 90° E) at 10 sec, and there is a gradual increase in the northern direction across the Ninetyeast Ridge. These observations are in accordance with the increase in the age of the ocean floor and there is a gradual increase in the group-velocity isolines. This can be interpreted as due to the hot uprising convection current, the material shows low shear-wave velocity along the ridge axis, and farther away from the ridge axis the material has become cooler with higher shear-wave velocity. The inversion of Rayleigh-wave group-velocity across the Ninetyeast Ridge shows 120-km-thick lvz (low-velocity zone) of shear-wave velocity of 4.38–4.78 km/sec at a depth of 40 km from the water surface, whereas other parts of the Indian Ocean show 44-km-thick lvz with shear-wave velocity of 4.12–4.17 km/sec at a depth of 40 km from the water surface. The high shear-wave velocity below Moho (4.19–4.75 km/sec) beneath the Ninetyeast Ridge indicates the presence of a cold and dense lithosphere beneath it.

Research paper thumbnail of Surface wave tomography studies beneath the Indiansubcontinent

Journal of Geodynamics, 1999

Research paper thumbnail of Anelasticity of the crust and upper mantle beneath the Eurasian continent and the nearby regions from the inversion of Love and Rayleigh wave attenuation data

Geophysical Journal International, 1982

The fundamental mode Love and Rayleigh waves generated by five earthquakes, which occurred in cen... more The fundamental mode Love and Rayleigh waves generated by five earthquakes, which occurred in central Asia and were recorded at 20-35 WWSSN stations throughout the world, are analysed. The Love and Rayleigh wave attenuations are determined at the time period of 10-120s for the continental and oceanic paths across Eurasia and nearby regions using the spectral amplitudes of these waves. The large standard deviation observed in the attenuation coefficients of surface waves may be due to the regional variation of the attenuative properties of the crust and upper mantle beneath Eurasia. The continental Rayleigh wave attenuation coefficients are smaller by a factor of up to 2 compared to oceanic paths. The continental Rayleigh wave attenuation coefficient attains two minima of 0.1 5 x and 0.1 1 x 10-3km-1 at the time periods of 3 5 and 80 s respectively, and two maxima of 0. 5 8~ and 0.3 x 10-3km-' at time periods of 10 and 100s respectively. A similar trend is observed for the oceanic paths as well. Backus and Gilbert inversion theory is applied to these Love and Rayleigh waves attenuation data to obtain Qj' models for the crust and upper mantle beneath Eurasia and the nearby regions. Independent inversion of continental Love and Rayleigh waves attenuation data yields the thickness of the lithosphere to be 90 km. For the oceanic paths, the thickness of the lithosphere is estimated t o be 110 km. The base of the lithosphere is identified as the depth at which QF' increases sharply. Qj' in the asthenosphere is greater to a minimum of a factor of 2 as compared to the lithosphere.

Research paper thumbnail of Surface-wave radiation pattern and source parameters of Koyna earthquake of December 10, 1967

Bulletin of the Seismological Society of America, Jun 1, 1975

Page 1. Bulletin ot the Seismological Society of America. Vol. 65, No. 3; pp. 711-731. June 1975 ... more Page 1. Bulletin ot the Seismological Society of America. Vol. 65, No. 3; pp. 711-731. June 1975 SURFACE-WAVE RADIATION PATTERN AND SOURCE PARAMETERS OF KOYNA EARTHQUAKE OF DECEMBER 10, 1967 ...

Research paper thumbnail of Determination of upper mantle velocity structure using the P and S waves spectra

Annals of Geophysics, 2010

Research paper thumbnail of Quasi-continental oceanic structure beneath the Arabian Fan sediments from observed surface-wave dispersion studies

Bulletin of the Seismological Society of America, 1988

The fundamental and higher modes of surface waves generated by 31 earthquakes and recorded at sei... more The fundamental and higher modes of surface waves generated by 31 earthquakes and recorded at seismographic stations along the western margins of India and Pakistan (Trivandrum, Kodaikanal, Goa, Bombay, Poona, New Delhi, Nillore, and Quetta) are used to estimate the crustal structure beneath the Arabian Fan sediments. The sedimentary thickness is determined from the observed higher mode data. The observed dispersion data suggest an increase in crustal thickness northward, from an approximately 16 km crustal thickness at the southern tip of India (Trivandrum) to an approximately 28 km crustal thickness at the regions of 20°N and above latitude, with an overlying 6 km sedimentary thickness. This gradual increase in crustal thickness in the northward direction and the attaining of quasi-continental oceanic (transition from continent to ocean) structure beneath the Arabian Fan sediments suggest that the Mohorovičić discontinuity may have resulted from a change in crystal structure due t...

Research paper thumbnail of Source parameters of the Burma-India border earthquake of July 29, 1970, from body waves

Tectonophysics, 1978

Abstract The source parameters are determined for the Burma-India border earthquake of July 29, 1... more Abstract The source parameters are determined for the Burma-India border earthquake of July 29, 1970, from body-wave spectra. We obtain seismic moment [ M o (P) = 4.83 , M o (S) = 3.40 ] · 1026 dyne cm, source dimension [ r (P) = 22.5, −r (S) = 27.7 ] km, radiated energy [ E R (P) = 7.19 , −ER (S) = 1.35] · 1020 ergs and the stress drop = 11 bars.

Research paper thumbnail of Crust and upper-mantle velocity structure beneath the northern and central Indian Ocean from the phase and group velocity of Rayleigh and Love waves

Physics of the Earth and Planetary Interiors, 1988

Research paper thumbnail of Spectral analysis of body waves for earthquakes and their source parameters in the Himalaya and nearby regions

Physics of the Earth and Planetary Interiors, 1979

Research paper thumbnail of Q-structure beneath the Tibetan Plateau from the inversion of Love- and Rayleigh-wave attenuation data

Physics of the Earth and Planetary Interiors, 1982

Research paper thumbnail of Seismotectonics of the Himalaya and its vicinity from centroid-moment tensor (CMT) solution of earthquakes

Journal of Geodynamics, 2000

Research paper thumbnail of Shear-wave velocity and attenuation structure beneath Antarctica determined from surface waves

Geophysical Journal International, 1994

Research paper thumbnail of Transitional continental-oceanic structure beneath the Norwegian Sea from inversion of surface wave group velocity data

Geophysical Journal International, 1999

Research paper thumbnail of Rayleigh-Wave Group-Velocity Studies beneath the Indian Ocean

Bulletin of the Seismological Society of America, 2005

The fundamental mode Rayleigh wave generated by 16 earthquakes, which occurred in the Indian Ocea... more The fundamental mode Rayleigh wave generated by 16 earthquakes, which occurred in the Indian Ocean and were recorded at 14 seismic stations of Asia, Africa, and Australia, are analyzed to estimate the Rayleigh-wave group velocity at periods of 10 to 60 sec by using the multiple filter analysis technique. In addition to this, Rayleigh-wave group-velocity data available in the literature across different propagation paths of the Indian Ocean forming a dense distribution of seismic wave traverses have been considered for tomographic studies. The group-velocity distribution maps have been obtained at periods of 10, 20, 30, 40, 50, and 60 sec for the Rayleigh wave. The minimum value of the group velocity of 2.0 km/sec is centered near the Rodriguez triple junction (25° S, 70° E) at 10 sec and higher value (3.4–4.0 km/sec) at 20 sec and greater period. As we move in the north-northwest direction from the Rodriguez triple junction, the Rayleigh-wave group-velocity isolines at 10 and 20 sec are also increasing in the northern direction in both the east and west sides of the ridge axis. Another minimum value of group-velocity isolines (1.9 km/sec) is centered near (25° S, 90° E) at 10 sec, and there is a gradual increase in the northern direction across the Ninetyeast Ridge. These observations are in accordance with the increase in the age of the ocean floor and there is a gradual increase in the group-velocity isolines. This can be interpreted as due to the hot uprising convection current, the material shows low shear-wave velocity along the ridge axis, and farther away from the ridge axis the material has become cooler with higher shear-wave velocity. The inversion of Rayleigh-wave group-velocity across the Ninetyeast Ridge shows 120-km-thick lvz (low-velocity zone) of shear-wave velocity of 4.38–4.78 km/sec at a depth of 40 km from the water surface, whereas other parts of the Indian Ocean show 44-km-thick lvz with shear-wave velocity of 4.12–4.17 km/sec at a depth of 40 km from the water surface. The high shear-wave velocity below Moho (4.19–4.75 km/sec) beneath the Ninetyeast Ridge indicates the presence of a cold and dense lithosphere beneath it.

Research paper thumbnail of Surface wave tomography studies beneath the Indiansubcontinent

Journal of Geodynamics, 1999