Identification of Site Effects and Bedrock Motion from Recorded Surface Response

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

Seismic analysis of structures cannot be carried out accurately unless site effects are taken into account. Moreover, presently available empirical attenuation relationships for predicting ground surface motions are only useful if site effects are considered. While an extensive collection of analytical and numerical techniques is available to analyze ground responses induced by bedrock motions, their accuracy depends on a priori knowledge of site properties and the availability of bedrock motions. In estimation of site effects, back-calculation of a site’s transfer function from earthquake-induced recorded signals is an attractive alternative. Most of the existing site response identification methods rely on a strategically chosen reference station. The approach presented here obviates the need to have the bedrock motions, which are unavailable in most real-life cases. In the method proposed herein, the site response is identified from recorded ground surface accelerations at two or more nearby stations through a blind identification technique, under the assumption that the unknown bedrock motion is identical for these stations and these stations have different site properties. We demonstrate the performance of this new approach using a synthetic but adequately realistic example. The said verification study makes use of vertically propagating shear waves—a common assumption in site response analyses. Nevertheless, the proposed identification algorithm does not require this one-dimensional wave propagation assumption as long as we can write a single-input-single output transfer function relationship between the common unknown bedrock motion and the ground surface motions.

Presenting Author: Asli Kurtulus

Authors