The strain rate and moment deficit along Indian Plate boundary: a tool for estimation of earthquake hazard

Abstract

The 1252 GPS stations horizontal velocity data is used to calculate the strain rate. The interpolated scalar strain field data has generated a continuous strain map. The 10 areas displaying greater than 104 nstrain/yr are marked as seismic source zones (A to J) which show a low b-value range between 0.53 and 0.73. The zones A to F in foothill Himalaya are areas of fault interactions. The interactions take place between Tertiary Himalayan Thrusts and Proterozoic transverse faults. The older Proterozoic transverse faults are integral part of basement ridges on underthrusted rigid Indian plate, which are being reactivated during Himalayan orogenesis. Such fault interactions are also seen along Eastern Himalayan Syntaxis (G) and Sagaing Fault (I) in Burmese arc, where faults from two different tectonic domains are interacting and getting activated by overall clockwise rotational mass movement around plate interface. In this study, we have computed both geodetic moment rates (Mg) and seismic moment rates (Ms) for all 10 zones; and compared them by the ratio (Mg/Ms). The geodetic strain rates are used to calculate Geodetic moment rates within a seismic volume of 15±2 Km depth. Seismic moment rates are computed from the earthquake catalogue of 100 years. From the moment deficit (i.e. the difference between Mg and Ms), the probable magnitude (Mw) of impending earthquake in 10 seismic source zones are estimated, the value ranges from 6.5 to 7.4 Mw. We infer that Zone F (Arunachal Himalaya), I (Sagaing fault), G (EHS) and A (Himachal Himalaya) are posing high seismic threat with occurrence of shallow focus 7.1 Mw earthquake at any moment.