Understanding the Physical Causes of Surface Wave Amplitude Variations across Eastern Asia through Seismic Waveform Simulation

Abstract:

Understanding the physical causes of surface wave amplitude variations is essential in many aspects of seismology, including estimation of the magnitude of earthquake/anthropogenic events, study of the attenuation properties of Earth’s interior, and analysis of the ground motion for engineering seismology and hazard assessment. This topic remains challenging in part due to the lack of high-quality earth models, and also because numerous factors may significantly affect surface wave amplitudes. These include: 1) source directivity, 2) anelastic attenuation, 3) multipathing and focusing/defocusing, and 4) local amplification.

To better understand the physical causes of the surface wave amplitude variations across Eastern Asia, we model seismic wave propagation using the crustal and uppermost mantle model constructed by Shen et al. (2015), which was produced using surface wave datasets and which captured many geological features. We apply the spectral element method (SEM) and a node-based finite-difference approach perform Rayleigh wave waveform modeling across Eastern Asia.

By measuring and analyzing the results of the surface wave waveform modeling, we separate and quantify the effects on surface wave amplitudes; notably , focusing/defocusing and local amplification effects. Our results illuminate the causes of observed amplitude variations across Eastern Asia from earthquake and anthropogenic sources and guide future research based on surface wave amplitudes.