Global variations in Fourier site response from instrumental observations

Abstract

Fueled by the advancement in sensor technology and increased seismicity, repeated observations of earthquake-induced ground shakings are accumulated at an unprecedented number of instrumented sites around the globe. Thus, the repeatable (or average) site responses at those recording stations can be disentangled from other systematic effects underlying ground-motion phenomena using regional-network-based approaches, e.g., generalized inversion technique or mixed-effect regression. This provides an excellent opportunity to gain new insights into the global variations in site response, which is impossible via regional studies only. In addition, site response inferred from weak motions based on Fourier amplitude spectrum (FAS), in comparison to that of response spectrum, can maintain the linearity of site response at all frequencies, facilitating a more straightforward physical interpretation. Capitalizing on the high-quality point-observations of Fourier site response in New Zealand, Japan, Europe, and California, we aim to unravel the physical drivers underlying the regional variations in site response, and infer globally consistent patterns, which are essential for developing predictive models transferable across regions. In this preliminary work, we report the global variations in the scaling of Fourier site response with commonly used site characterization parameters/proxies.