Fundamental Site Period and Peak Amplification Maps for the Jackson Purchase Region in the New Madrid Seismic Zone

Session: Near-Surface Effects: Advances in Site Response Estimation and Its Applications [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Site response, site resonance in particular, is of great concern in the New Madrid Seismic Zone because there are many communities underlain by soft sediments overlying hard bedrock, resulting in significant impedance contrasts and potential ground-motion amplification. The NEHRP site classification, which is based on the time-weighted average shear-wave velocity of the top 30 m of the soil/rock column (i.e., Vs30), has been widely used to produce microzonation maps of such potential ground-motion amplification. However, Vs30 does not physically and uniquely correlate to site response, site resonance in particular. In other words, Vs30-based maps may not capture site response and thus may not be appropriate for mitigation and engineering applications.

Primary site response characteristics can be quantified by two parameters: the fundamental (i.e., base mode) site period, T₀, and the corresponding amplification, A₀. We derived T₀ and A₀ using theoretical 1-D site-response analysis and simplified one-layer sediment-over-bedrock earth models for the Jackson Purchase Region in western Kentucky from shear-wave velocity profiles derived from surface reflection/refraction surveys. We also measured the fundamental site periods and their peak amplifications from earthquake S-wave H/V spectral ratios at seismic and strong-motion stations in the region. We combined the results from theoretical and empirical analyses to produce fundamental site period and amplification maps for the region.

Presenting Author: Yichuan Zhu

Authors