Seismic velocity structure and intraplate seismicity beneath the Deccan Volcanic Province of western India
статья в журнале
(ИНГГ СО РАН)
дата публикации: 2019
The northwestern Deccan Volcanic Province (NWDVP) in India has undergone major tectonic changes during the Eocene-Paleocene, when voluminous eruptions took place due to interaction of the Indian plate with the Reunion plume. The intense seismic activity makes this region as the most vulnerable intraplate earthquake zones, world over. In this study, we utilize arrival times of 40,499 P and 39,581 S phases from waveforms of 5653 events registered at 93 seismic stations to obtain high-resolution tomographic images of the crust and uppermost mantle beneath the NWDVP. The images shed light on the relation between seismicity and seismic structure in the source regions of two large earthquakes (Mw ≥ 7.7) at depths >20 km in the rift basins, shallower moderate (Mw ∼5) quakes and swarm induced activity in the horst region. Higher Vp/Vs ratios are observed for the seismogenic rock matrix with entrapped magma fluid that played an important role in triggering large and moderate tectonic earthquakes. High Vp/Vs ratios are also observed in the uppermost crust, indicating that fluid in sediments/fractures triggers the swarm and induced seismicity. The source zones of the shallow, mining induced seismicity are imaged as low Vp, Vs zones. The vertical and horizontal intrusions of the Deccan volcanic magma in the uppermost mantle and lower crust are also well imaged as high Vp and Vs anomalies. Variations in the depth to the Moho and lower crustal velocities signify alterations due to tectonic processes during different time scales.
первоисточник: Physics of the Earth and Planetary Interiors