Blind deconvolution methodology for site-response evaluation exclusively from ground-surface seismic recordings

A novel blind deconvolution methodology for identification of the local sit e characteristics based on two seismograms recorded on the free surface of a sediment site is presented. The approach does not require recordings at d epth nor at a nearby rock outcrop, and eliminates the need for any prior pa rameterization of source and site characteristics. It considers that the su rface recordings are the result of the convolution of the 'input motion at depth' with transfer functions (channels) representing the characteristics of the transmission path of the waves from the input location to each recor ding station. The input motion at depth is considered to be the common comp onent in the seismograms (same input in a statistical sense). The channel c haracteristics are considered to be the part in the seismograms that is non -common, since the travel path of the waves from the input motion location at depth to each recording station is different, due to spatially variable site effects. By means of blind deconvolution, the algorithm eliminates wha t is common in the seismograms, namely the input motion at depth, and retai ns what is different, namely the transfer functions of the site from the in put location to each recording station. It estimates the site response in b oth frequency and time domains, and identifies the duration of the site's t ransfer functions. The methodology is applied herein to synthetic data at r ealistic sites for performance validation. The blindly estimated results ar e in almost perfect agreement with the actual site characteristics, indicat ing that the approach is a promising new tool for seismic site-response ide ntification from recorded data. (C) 1998 Elsevier Science Ltd. All rights r eserved.