3D seismic wave amplification in the Indo-Gangetic basin from spectral element simulations

S. Jayalakshmi, J. Dhanya, S. T.G. Raghukanth, Paul Martin Mai

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Abstract

This study investigates seismic wave amplification effects in the Indo-Gangetic (IG) basin for possible large earthquakes in the region using spectral-element simulations. The Indo-Gangetic basin is a large and deep sedimentary basin that covers the northern part of India, in which several mega-cities are located, including the capital city of New Delhi. The seismicity in the region due to presence of many active tectonic faults is an important matter of concern for engineers. The damage caused in a future large earthquake could affect a huge population and hinder the development of numerous large-scale industrial establishments. Due to local soil conditions and the structural complexity of the sedimentary basin, seismic wave amplification is expected. However, the absence of seismic data for large earthquakes and limited knowledge of the structure of the basin poses challenge in estimating shaking amplifications. Therefore, we model the 3D structure of the basin using Spectral Finite Element method (Specfem3D) including the topography of the Himalayan mountains, and compute synthetic seismograms for a suite of simulated rupture scenarios. First, we use two past earthquakes in the basin to calibrate our 3D model by comparing the simulated ground motions with the recorded data. Later, we consider realizations of potential future large earthquake (Mw 7.1), by generating different kinematic rupture models. We simulate earthquake scenarios for different source parameters to quantify the statistics of expected ground shaking levels. We then infer seismic wave amplification as a function of both frequency and basin depth for complex seismic sources. Our results indicate a maximum amplification of 16 in Peak Ground Velocity (PGV) and 19–35 in Spectral Accelerations (Sa) at long periods. The results presented in this study may be useful for engineers to predict ground motions for future large earthquakes in absence of any available seismicity data.
Original languageEnglish (US)
Pages (from-to)105923
JournalSoil Dynamics and Earthquake Engineering
Volume129
DOIs
StatePublished - Nov 12 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): BAS/1339-01-01
Acknowledgements: This research has been supported by King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia, grants BAS/1339-01-01 and URF/1/3389-01-01. We thank Daniel Peter for helpful suggestions to improve the resolution of our 3D model and Spectral finite element mesh by running several test cases. We also thank Percy Galvez Barron for providing useful python scripts to efficiently take into account many scenario earthquakes simultaneously in the simulation. We are greatly indebted to Samuel Kortas for optimizing the computation time of our post processing scripts. All the simulations have been carried out at KAUST Supercomputing Laboratory (KSL), and we thank the support of the KSL staff.

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