Hazard analysis of earthquake in Pleret, Bantul Regency, Yogyakarta Special Region based on microtremor data

Abstract

Pleret, one of the sub-districts in Bantul Regency, Yogyakarta, is prone to earthquakes. This area is traversed by an active fault system known as the Opak fault, with a maximum magnitude of 6.6 Mw. The local geological conditions can be determined based on microtremor data from 43 measurement points. The purpose of this research is to understand the dynamic characteristics of the local geological conditions, including the dominant frequency (f0), shear wave velocity (Vs30), peak ground acceleration (PGA), and to map the earthquake impacts on the population and structures. Microtremor measurements were conducted for approximately 20 minutes, revealing a dominant frequency range of 0.61-10.85 Hz. The HVSR curve inversion revealed the Vs30 range 213 to 826 m/s distribution. Peak Ground Acceleration (PGA) values varied from 0.16 to 0.26 g. Using InaSAFE software, the estimated affected population reached 49,052 people, with over 23,176 structures affected. The results of this mapping are expected to be utilized as a step towards enhancing disaster preparedness.