Using stochastic point source model to study the site effect in Lan-Yang plain

Kun-Ying Chou

Abstract

The purpose of this study is using the method of stochastic point source model to analyze the site effect in the Lan-Yang plain. We used dense TSMIP strong motion measurements to study the local site effect, which are considered by soil to rock spectral ratios calculated between spectra of two selected earthquakes records and rock site modeled by stochastic model.

In this study, we analyzed site effect by applying spectra-ratio technique, and the dominant frequency and amplification in each frequency indicate clearly the form of local site effects. The model calibration is proceeded by the records at Site class B ILA stations. The calibrated model parameters is used to simulate ground motions at soil sites for calculating amplitude spectrum and then estimated by the spectra-ratio technique.

In Lan-Yang plain the Dominant frequency range is from 1 to 3Hz, but higher than 3Hz in the boundary of plain. It represents the depth of basement become shallow near the edge of plain. The result shows that the lower frequency response calculated by stochastic model is lower than usual, but it takes advantage of calculating the average transfer function with lots of events in order to make more objective explanation.

Reference

Boore, D. M., and W. B. Joyner (1997). Estimation of ground motion at deep-soil sites in eastern North America, Bulletin of the Seismological Society of America, 87,327–341.

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Boore, D. M. (2005). SMSIM – Fortran programs for simulating ground motions from earthquakes: version 2.3 – A revision of OFR 96-80-A, U.S. Geol. Surv.

(Abstract)(Full text)