TOPOGRAPHICAL ASPECTS OF SEISMIC HAZARD

Abstract

Many seismic hazards. like landslides, occur mostly in regions of high topographical elevations. A quantitative assessment of topography can be a useful tool for identifying zones of active landslides, particularly those associated with seismic hazards. The main objective of this study was to estimate slope angles in the vicinity of earthquakes in known seismogenic source zones, so that landslide potential can be estimated. The Kangra Seismic Source zone (KSSZ), (Mriclula et al., 2014), which is the most active seismic source zone in western Himalaya, is the study area. It is located between latitude 31°-35°N and longitude 75°-78°E in the Western Himalayas, and covers parts of Jammu & Kashmir and Himachal Pradesh. Several earthquakes, with Mw range 6.2 to 8.0 for the period 1905 - 1945, and ISRO topographical sheets 521), 52H and 431? were used for obtaining elevations in the study area. Hazard parameters (Me, b, a, Xrn, M11) estimated in Kangra SSZ were 3.8. 1.93, 0.51, 0.982 and 8.71, respectively, and return periods estimated for 8.0, 7.0, 6.0 magnitude earthquakes were 141 years, 44 years and 14 years, respectively. Topographical aspect related to maximum and minimum elevation was considered within a pre defined buffer zone drawn around each epicenter, and slope angles were computed to assess landslide hazard. This study indicates that landslides will compound the disaster if the probability of occurrence of a great earthquake in the next 50 years is considered as per hazard parameters.