3:30 PM - 4:30 PM
[S02-P-02] 3D Poroelastic Modelling of Reservoir Triggered Seismicity (RTS) in Koyna Region, Western India
Reservoir triggered seismicity (RTS) is a well known phenomenon and about 120 sites have been identified worldwide where earthquakes have been triggered by filling of artificial water reservoirs. The Koyna region near the west coast of India is one of the globally recognised sites of RTS, where earthquakes have been occurring in a small area of 20 x 30 km2 since the impoundment of Koyna reservoir in 1962. Till date 22 earthquakes of M>5 have been occured in this region including largest triggered earthquake of M6.3 on 10 December 1967. RTS can be interpreted as a result of stress and pore pressure changes due to poroelastic response in the rock matrix. Although numerous studies have been carried out to constrain the mechanism of triggered earthquakes, a satisfactory model for this region remains elusive. Based on poroelastic theory we have used 3D finite element model (FEM) to simulate the development of stress and pore pressure due to reservoir impoundment. First we develop poroealstic model to investigate the effect of reservoir impoundment on local seismicity of the region. Preliminary studies suggest that impoundment of Koyna reservoir altered the pore pressure in the region and formed pore pressure front that propagated up to seismogenic depth through the crust with fluid diffusion. The change in stress regime of the region by the seasonal fluctuation in water level of the reservoir is found to be associated with the ongoing seismicity. However, measurements of different properties (Bulk modulus, Young's modulus, Poission's ratio, porosity, permeability etc.) through the ongoing deep drilling programme in Koyna region would provide a more realistic model of RTS.