Site Response Mapping at Pulau Pinang, Malaysia Using the Horizontal-to-Vertical Spectral Ratio Technique and Multichannel Analysis of Surface Waves

Evaluation of the soil site response is vital for the mitigation and preparedness of strong ground shakings of earthquake type. Among several techniques available, both the horizontal-to-vertical spectral ratio (HVSR) and the multichannel analysis of surface waves (MASW) were adopted because of their feasibility and suitability for the study area. A dense population and several strategic hi-tech industries characterize the study area. The current work is motivated by the need to prepare a mitigation and preparedness plan for a future large earthquake. Although both techniques can be conducted separately to quantify the soil response, the present study adopted a joint analysis of both methods to fill the shortcomings of both. For instance, the HVSR technique faces a debate that peak amplitude does not represent the expected accurate amplification. This resulted from the discussion on the nature of the ambient seismic noise used for the HVSR analysis. To overcome this, the research adopted the HVSR and MASW survey conducted at 110 sites considered in this work. The aim is to use the 1-D transfer function deduced from MASW to build a model to obtain the amplification factor through regression analysis. This will end up with an equation to correct the amplification factor obtained from HVSR. The regression gave bad fitting when using the undamped 1-D transfer function. However, the fitting has significantly improved when using the damped 1-D transfer function. The model obtained applies to the Penang peninsula and may help with a more realistic seismic hazard assessment.