Site characterization evaluation in Perth Metropolitan Area using microtremor array method

Perth is the largest city in Western Australia and home to three-quarters of the state's residents. In recent decades, there has been a lot of earthquake activity just east of Perth in an area known as the South-West Seismic Zone. The latest study shows that PGA on rock site in Perth Metropolitan Area (PMA) is estimated ranging from 0.14g in the north-east through to 0.09g in the south-west for a return period of 475 years. The numerical results of site response analysis based on limited available geology information for PMA also indicate that Perth Basin might amplify the bedrock motion by more than 10 times at some frequencies and some sites. Hence, more detailed studies on site characterization and amplification are necessary. The microtremor method using spatial autocorrelation (SPAC) processing is a useful tool for gaining thickness and shear wave velocity (SWV) of sediments and has been adopted in many previous studies. In this study, site characterize evaluation in PMA is performed using SPAC method. The soil profiles of representative PMA sites are determined. Nonlinear site responses are then calculated. The response spectra on soil sites are estimated and compared with the respective design spectrum defined in the Current Australian Earthquake Loading Code. Discussions on adequacy of the design spectrum are made.