Using the fourier spectral ratios to analyze the soil nonlinear site response.
Chang, Chih-Wei
Abstract
We use two methods which are the two stations spectral ratios and the Horizontal-to-Vertical spectral ratios (single station) to identify the soil nonlinear response at two strong-motion arrays in Taiwan. They respectively are the SMART2 array and the SMART1 array which includes the LSST array. First, we calculate the frequency-dependent soil amplification functions as a ratio of the spectra at soil to rock site stations. Second, we use horizontal-to-vertical spectral rations of surface soil recordings at a single station. Then, we compare (1) the average spectral ratios on weak and strong motions, (2) the ratios for the mainshocks and aftershocks, and (3) the ratios for the strong shear waves and their coda; above two methods. We attribute the observed discrepancies between weak and strong motion amplification functions to the differential nonlinear response occurring at rock and soil sites. Our results demonstrate above two methods are sensitive to nonlinear ground response at both arrays in Taiwan.
Reference
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