Kajian probabilistic seismic hazard analysis sebagai dasar mitigasi risiko gempa bumi di Kota Bengkulu

Bengkulu City is one of the regions in Indonesia with a high level of seismicity due to its proximity to the subduction zone and active fault systems, making seismic hazard assessment essential to support risk mitigation efforts. This study aims to analyze the probabilistic seismic hazard in Bengkulu City using the Probabilistic Seismic Hazard Analysis (PSHA) method. Earthquake data were obtained from the catalogues of the Meteorology, Climatology, and Geophysics Agency (BMKG) and the United States Geological Survey (USGS), covering the period from 1900 to 2025. All earthquake data were homogenized into moment magnitude (Mw) to ensure analytical consistency. The declustering process was carried out using ZMAP 7.0 software to separate mainshocks from foreshocks and aftershocks, as well as to determine seismic parameters in the form of a-values and b-values for each seismic source. The PSHA was subsequently performed using SR.Model software to obtain spectral acceleration values at periods of T = 0 seconds (Peak Ground Acceleration/PGA), T = 0.2 seconds, and T = 1 second with a probability of exceedance of 2% in 50 years. The results indicate a PGA value of 0.6523 g, which is consistent with the acceleration values presented in the 2022 Indonesian Seismic Hazard Map (PusGen 2022). Deaggregation analysis shows that the Musi Fault is the dominant seismic source, contributing 64.70%, with a dominant distance of 52.61 km and a dominant magnitude of Mw 6.71. The findings of this study are expected to serve as a reference for earthquake-resistant structural design and the development of earthquake disaster mitigation strategies in Bengkulu City.