Segmentation of Main Boundary Thrust and Main Central Thrust in Western Himalaya for assessment of seismic hazard

During an earthquake, longer faults and lineaments may not rupture over their entire length, but may do so in smaller segments depending on some physical boundary in the fault that controls and defines the location and extent of rupture, which may be governed by several factors such as presence of transverse tectonic features, change in seismicity pattern along the fault, difference in slip rates, occurrence of significant lithologic changes, strike of fault, etc. This paper is an attempt to identify segments of two megalineaments of Western Himalaya, viz. the Main Boundary Thrust (MBT) and Main Central Thrust (MCT). This was attempted by subjecting seismicity and tectonic data in a 7° × 7° study area to a pattern recognition technique. Six segments of the 997-km-long MBT and five segments of the 800-km-long MCT were obtained in the study area. These segments, along with other tectonic features and seismicity of the region, were included in assessment of seismic hazard and preparation of peak ground acceleration (PGA) maps.