Modeling of Ground Motion in the National Capital Region, India for a Recorded 4.9 Magnitude Earthquake and for a Future, Large 8.5 Magnitude Earthquake in the Himalayan Central Seismic Gap

Session: Numerical Modeling of Rupture Dynamics, Earthquake Ground Motion and Seismic Noise
Type: Oral
Date: 4/29/2020
Time: 11:15 AM
Room: 230 + 235
Description: 

In this study we model the ground motion in the National Capital Region (NCR), India of a moderately sized earthquake of July 22, 2007 of magnitude M4.9 with the epicentre near Tehri in the Garhwal-Kumaon Himalaya which is part of the Central Seismic Gap (CSG) and is recognized to have accumulated large strain energy with the characteristic lack of large magnitude earthquakes and partial/incomplete stress drop mechanisms. We simulate the high frequency ground motions at five sites in the NCR which may be about 200-300 km from the rupture area, by employing the empirical Green’s function (EGF) technique. The ground motions are simulated for a hypothetical Mw 8.5 earthquake. The simulation uses the different stress drop ratio between the M4.9 and M8.5 event at the investigated sites. The computed PGA (Peak Ground Acceleration), PGV (Peak Ground Velocity) and PGD (Peak Ground Displacement) range between 0.83 m/s² and 5.19 m/s², 0.3 to 0.25 m/s and 0.002 to 0.02 m respectively. The response spectra for acceleration, velocity and displacement for both moderate and simulated events are compared for useful insights of the structural design criteria for hazard analysis. Due to most of the region being underlain by fluvial deposits from the Yamuna river, most of the sites reveal that the seismic hazard in NCR seems high. In such a scenario, the possible site amplification, predominant site frequencies and response spectra for acceleration, velocity and displacement are estimated and compared for both moderate size M4.9 and simulated M8.5 earthquakes. This study provides valuable information of the acceleration time histories and seismic hazard in the NCR arising out a large earthquake of M8.5 occurring in the active Himalayan arc region.

Presenting Author: Sivaram Krishnavajjhala

Authors