SEISMIC HAZARD OF THE UTTARAKHAND HIMALAYAS BASED ON POSSIBLE SCENARIO DUE TO GREAT EARTHQUAKE

Abstract

The semiempirical approach based on envelope summation method given by Midorikawa (Tectonophvsics 218:287-295, 1993) has been modified here for modeling of strong motion generation areas (SMGAs). 1-lorizontal components of strong ground motion have been simulated using modifications in the semiempirical approach given by Joshi el al. (Nat 1-lazard 7 1:587-609, If 2014). Various modifications in the technique account for finite rupture source, layering of earth, componentwise division of energy and frequency-dependent radiation pattern. in this work, SMGAs of the Uttarkashi earthquake have been modeled. Two different isolated wave packets in the recorded accelerograms have been identified from recorded ground motion, which accounts for two different SMGAs in the entire rupture plane. The approximate locations of SMGAs within the rupture plane were estimated using spatio-temporal variation of 77 aftershocks. Source parameters of each SMGA were calculated from theoretical and observed source displacement spectra computed from two different wave packets in the record. The final model of rupture plane responsible for the Uttarkashi earthquake consists of two SMGAs, and the same has been used to simulate acceleration records at different station using modified serniempirical technique. Comparison of the observed and simulated acceleration records in terms of root mean square error confirms the suitability of the final source model for the Uttarkashi earthquake.