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Exploration of Shallow S-wave Velocity in Bandung Basin using Surface S-wave Velocity and H/V Method
Pramatadie A.M.
6th Asia Pacific Meeting on Near Surface Geoscience and Engineering Smart Technologies Kind to the Planet
Abstract
Summary S-wave velocities become one of important parameters for seismic hazard evaluation. It can quantify the amplification and the resonant frequency of ground motion. This study aims at providing shallow S-wave velocity profiles in the Bandung basin. We apply the surface S-wave velocity and horizontal-to-vertical microtremor spectral ratio (V1-H/V) method that simplify a profile representation of an estimated profile by a linear function of S-wave velocity. The model parameters become only the V1, the velocity-depth gradient, and the bedrock velocity. The result shows that most of the previous observed phase velocities can be well explained by the theoretical phase velocities that indicates the appropriateness of the profile representation using the linear function in the Bandung basin. Furthermore, we applied the method to provide 29 additional S-wave velocity profiles in the basin. The gradient can be estimated based on the agreement of the peak frequencies of the observed microtremor H/V and the theoretical ellipticity of the fundamental mode of the Rayleigh wave. The estimated Vs profiles in the Bandung basin suggest that the time-averaged S-wave velocities in the top 30 m (Vs30) are below 150 m/s at sites located in the lake deposit, especially in the central-eastern part of the basin.