Simulation of a plausible great earthquake (Mw 8.0) sourced on down-going Indian slab beneath Indo-Burmese wedge and its implications for North East (NE) Indian region

Abstract

The 4th January 2016 Manipur earthquake (Mw 6.7) occurred along the Indo-Burmese wedge and ruptured towards NW direction causing severe damage to buildings/structures in North-East (NE) Indian region. A plausible earthquake (Mw 8.0) is simulated to estimate the ground motions and associated seismic hazard by means of the waveforms of 2016 Manipur earthquake (Mw 6.7) as an element earthquake considering the source in the subduction boundary of the Indo-Burmese wedge at an intermediate depth. The empirical greens function mechanism (EGFM) is adopted to accomplish the better utilization of the observed ground motions of the recorded earthquake as an element earthquake and to achieve the probable ground motions in order to acquire the appropriate path/site effects in the simulated ground motions. The obtained results demonstrate the impact of the comparable rupture directivity pattern in both element as well as the simulated earthquakes. The Peak Ground Acceleration (PGA) in NE India from element and simulated earthquakes vary from 3 cm/sec2 and 11 cm/sec2 to 103 cm/sec2 and 342 cm/sec2 at epicentral distances of 624 km and 53 km respectively. The high amplitude surface waves due to the interference of seismic waves along with the combined effects of rupture directivity and site amplification showcased the highest PGA value at Shillong (SHL). This site is located on Pre-Cambrian rock and situated at an epicentral distance of 214 km from the source zone, which is lying at an intermediate depth that might have propelled the direct seismic waves of higher intensity at a longer distance compared to other sites. The outcome of the present study highlights the significance of varied ground motion parameters among the observed sites to the extent of bearing the damage potential of strong ground motions. The related analysis also advocates for the simulated PGA variations and associated duration of the earthquake waveforms exposed on different geological formations that have strong bearings on the seismic risk involved with future probable great earthquake in the study region. Moreover, simulated ground motions of expected plausible disastrous earthquakes on numerous geological formations beneath the various sites have significant impacts on designing critical structures/buildings such as schools, hospitals, bridges, dams and nuclear power plants for NE India. Thus, the detailed investigations on ground motion parameters, simulation of ground motion and the influence of different geological/geomorphological conditions on duration, shape and maximum amplitude of ground motion may be supportive for implementing earthquake risk and mitigation plans in order to assess the seismic hazard of the study region.