Estimation of Shear Wave Velocity Using Horizontal to Vertical Spectrum Ratio (HVSR) Inversion to Identify Faults in Pacitan

Abstract Pacitan is one of the cities in Indonesia which is located around a subduction zone with many faults. Grindulu Fault is one of the active faults in Pacitan. In order to mitigate hazard in the area, detailed information about the existence and characteristic of the fault is needed. Thus, imaging of Grindulu Fault using shear wave velocity (Vs) was carried out. 1-D of Vs was revealed by inversion of HVSR from microtremor data using the Monte Carlo algorithm. Furthermore, several Vs were processed using interpolation approach to determine two-dimensional (2-D) cross-section of Vs. Based on the contrast of Vs and considering the geological conditions in Pacitan area, the existence of Grindulu Fault and other faults were identified.