Deccan Trap Volcanism: A Local Driver of Medium-Scale Seismic Activity in Peninsular India
Daya Shanker
Affiliations: Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, India; (d.shanker@eq.iitr.ac.in)
Presentation type: Poster
Presentation time: Thursday 16:30 - 18:30, Room Poster Hall
Poster Board Number: 140
Programme No: 2.1.50
Abstract
Peninsular India (PI), spanning 8° to 25°N and 68° to 88°E, is also known as the Precambrian Shield and generally experiences low seismic activity compared to the more tectonically active Himalayan collision zone. However, the Deccan Traps, a vast and geologically significant volcanic formation covering about one-third of PI, represent the region's youngest and most prominent geological feature. While most of PI has an older, thicker crust and lithosphere, the Deccan volcanic activity persisted for roughly 4 million years, creating a Flood Basalt Zone (FBZ) where subsidence of adjacent crustal rocks into the upper mantle has occurred. Basalt solidus within these FBZs lies at depths between 22 to 36 km, and these zones are identified by distinct gravity anomalies. Seismic data from 1900 to 1993 indicate that the Deccan Traps are more seismically active than the rest of the shield, releasing about 4.5 times the energy. A model is proposed to explain how medium-sized earthquakes occur in this trap-covered region: undulations in the Moho boundary create faults and fractures, allowing fluid to enter the upper crust. This fluid accumulates in cracks, generating stress and potentially triggering seismic events. Acting as a lubricant, the fluid also facilitates fault slippage, making these areas susceptible to medium-sized earthquakes that could present future seismic hazards.