Shear Velocity (VS) Estimation with HVSR (Horizontal to Vertical Spectrum Ratio) Curve Inversion Method of Microtremor Measurement in Bandung Basin

Abstract

From the geological aspect, Bandung is a basin surrounded by mountain area. The stratigraphical setting of Bandung is also dominated by thick and soft sediment which makes Bandung needs a mitigation plans needed to reduce the risk of ground motion. Horizontal to Vertical Spectrum Ratio (HVSR) is a popular method developed by (Nakamura, 1989) in microtremor study to use for seismic characterization which is used in this research. This method is used to determine the seismic characteristic in Bandung Basin. The seismic characterization estimated in this research are amplification and dominant frequency. Those values are obtained from HVSR curves which then used to determine the shear wave velocity and depth of Bandung Basin with inversion method. Amplification value in Bandung Basin and its surrounding area is between 2-11.5 with its highest value is in the south-eastern part of observation area. The segmented amplification values based on natural period of building are varies in values based on the range of period and location points. The other seismic characteristic in this research is dominant frequency which value is between 0,1-8 Hz with the highest values are in the north and south part of observation area, while the middle part has the lowest value. Bandung Basin has low shear wave velocity underneath it which less than 800 m/s within depth more than 200 m of depth. There is also a high velocity structure which divide Bandung Basing into two major parts: west part and east part. Those seismic characteristics can be used as a guide to carry-on mitigation procedures to minimize the risk if any disasters happen.