Assessment of the Variability of Basin Nonlinearity and Near-Field Ground Motion in Kathmandu, Nepal Due to Obliquely Incident Seismic Waves

Session: Numerical Modeling of Rupture Dynamics, Earthquake Ground Motion and Seismic Noise [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The combination of source and site effects on seismic hazard is of great interest in the near field, and Kathmandu (Nepal) is a special area to study this phenomenon. It is situated in a sedimentary basin with a complex geometry over the active Main Himalayan Fault. It has been hit recently by the 1934 M 8.1 and the 2015 M 7.8 earthquakes. Although the magnitudes of the two earthquakes are close, their outcomes were surprisingly different: The first earthquake caused severe amplification of ground motion because of site effects and soil nonlinearity; the same basin behaved like a shock absorber by damping high-frequency energy during the latter. Our objective is to understand the origin of this variation by investigating the impact of earthquake source on nonlinear basin response and consequent near-field ground motion. Our approach is numerical modeling of 2D SV seismic wave propagation and nonlinear behavior of sedimentary soil deposits by using spectral element method. We particularly focus on the effect of incident wave angle and complexity of broadband source energy. The preliminary results of our study suggest that the incidence angle largely affects the basin nonlinearity and spatial variability of ground motion. The perspective is to extend our analyses from plane waves to kinematic rupture models for the 1934 and 2015 earthquakes.

Presenting Author: Elif Oral

Authors