DEVELOPMENT OF TIME AND MAGNITUDE PREDICTABLE MODEL FOR SEISMIC HAZARD ASSESSMENT IN CENTRAL HIMALAYAS

Abstract

The central Himalaya has been divided into six seismogenic sources on the basis of certain seismotectonic and geomorphological criteria. In each of these sources, interevent time between successive mainshocks with magnitude equal to or larger than certain cut-off magnitude are considered. These interevent times as well as the magnitudes of the mainshocks have been used to determine the following empirical relations. Log T = 0.20Mn in + 0.27M — 0.02log mo — 1.37 Mf 0.73M,,,;n + 0.09MP + 0.01 log m0_ 1.04 Where T, is the interevent time measured in years, Mmin is the surface wave magnitude of the smallest mainshock considered, Mp is the magnitude of the preceding mainshock, Mf is the magnitude of the following mainshock ,m0 is the yearly released moment in each source. These relations may be used for earthquake hazard assessment in the region. On the basis of these relations and taking into account the time of occurrence and the magnitude of the last mainshock in each seismogenic source, time dependent conditional probabilities for the occurrence of the next large (MS > 5.5) shallow mainshocks during the next 30 years as well as the magnitudes of the expected mainshocks are determined