Numerical Investigations on the Effect of Crustal Heterogeneities on the High Frequency Attenuation

Date: 4/24/2019

Time: 06:00 PM

Room: Grand Ballroom

Predicting the observed attenuation at high frequency remains an open issue of strong ground motion modelling. The main reason is the interaction of many factors such as intrinsic attenuation, crustal heterogeneity, source rupture mechanism among others. In practice, usually this phenomenon is taken into account via regression coefficients, such as kappa parameter introduced by Anderson and Hough in 1982 which will be used in ground motion prediction equations. The site response prediction and engineering design however, may be critically influenced by the choice of those parameters, regardless of the accuracy of the statistical analyses behind it.

In recent years, source-to-site numerical simulations have gained momentum due to the increasing availability of High Performance Computing resources. This allows the possibility to investigate some phenomena, such as the dispersive attenuation of seismic wave motion.

The heterogeneous nature of the crustal 3D scatter distribution leaves a high-frequency footprint on the wave-field recorded at the surface. The aim of this study is to show the impact of the 3D crustal heterogeneities on the travelling wave towards the surface, using high-fidelity earthquake numerical simulations. The objective is to highlight the apparent attenuation and the possible trapping effect due to the heterogeneities and also to characterize the high frequency part of the radiated seismic motion. This task is accomplished by inspecting the broad-band (0-25 Hz) obtained synthetic wave-forms for different scenario realizations. An estimation of the kappa value is provided at different locations, giving further insights on the uncertainty related to it.

Presenting Author: Martin Colvez

Authors