Understanding Ground Motion in Las Vegas: Insights from Data Analysis and Two-Dimensional Modeling

Rodgers, A ; Tkalcic, H ; McCallen, D

Lawrence Livermore National Laboratory

关键词: Data Analysis;    Nuclear Explosions;    Ground Motion;    Wave Forms;    58 Geosciences;   

DOI  :  10.2172/15013918
RP-ID  :  UCRL-TR-202220
RP-ID  :  W-7405-ENG-48
RP-ID  :  15013918

美国|英语

来源: UNT Digital Library

【 摘 要 】

Seismic ground motions are amplified in low velocity sedimentary basins relative to adjacent sites on high velocity hard rock. We used historical recordings of NTS nuclear explosions and earthquake recordings in Las Vegas Valley to quantify frequency-dependent basin amplification using Standard Spectral Ratios. We show that amplifications, referred to as site response, can reach a factor of 10 in the frequency band 0.4-2.0 Hz. Band-averaged site response between 0.4-2.0 Hz is strongly correlated with basin depth. However, it is also well known that site response is related to shallow shear-wave velocity structure. We simulated low frequency (f<1Hz) ground motion and site response with two-dimensional elastic finite difference simulations. We demonstrate that physically plausible models of the shallow subsurface, including low velocity sedimentary structure, can predict relative amplification as well as some of the complexity in the observed waveforms. This study demonstrates that site response can be modeled without invoking complex and computationally expensive three-dimensional structural models.