Estimation of strong ground motion in Southern Peninsular India by empirical Green's function method

Abstract

In the present study, strong motions are estimated at 17 stations in Southern Peninsular India (SPI) for the 7 February 1900 Coimbatore earthquake (Mw 6) using the empirical Green's function (EGF) method. The broadband recordings of three small earthquakes of ML 3.5, 2.9 and 3.0 respectively, are taken as EGFs to simulate ground motion. The slip distribution of the main event is considered as a von Karman random field. The stress drops of the three small events estimated from finite fault stochastic seismological model lie between 130 and 140 bars. The peak ground acceleration (PGA) values, an ensemble of acceleration time histories and response spectra, are estimated at all the 17 stations using corresponding EGFs, and the mean response spectra are reported. Another estimate of PGA is also obtained using the stochastic seismological model. The estimated PGA values from the two methods are compared to check the consistency of the results. It is observed that the mean PGA values are within the bounds of the maximum and minimum PGA values obtained from the EGF method, while the differences at some stations can be attributed to the local site conditions. The ground motions simulated in the present study can be used to perform nonlinear dynamic analysis for future and existing structures in the SPI region for any event of magnitude Mw 6.