Monsoon-induced earthquake activity in Talala, Gujarat, India

Abstract

We explore the possibility that the episodic swarm activity observed in the region around Talala is related to a poroelastic response of the seismogenic crust to surface water flux, leading to pore pressure changes at depth. In particular, we evaluate models where these pore-pressure changes result from rainfall-induced ground-water recharge with corresponding pore pressure diffusion into depth and reservoir-induced pressure changes related to two dams located around 10 km from the swarm region. Based on the observed reservoir and rainfall data, we estimate the time-dependent pressure variations in the active seismogenic volume and calculate the resulting seismicity rates assuming rate- and state-dependent frictional nucleation. Our results show that pore pressure variations can well explain the general observations, with highest correlations for the reservoir-triggering mechanism. However, the latter model requires unrealistically small values of effective normal stresses in the source region unless pore-pressure diffusion is guided by a highly permeable fracture zone.