Analisis Bahaya Gempa Bumi Menggunakan Metode Probabilistic Seismic Hazard Analysis (PSHA): Studi Kasus Provinsi Bengkulu

Abstract

Bengkulu Province is located in an active tectonic zone along the western coast of Sumatra, influenced by the Sumatra Megathrust subduction zone and the Great Sumatra Fault, making it highly susceptible to damaging earthquakes. Earthquake hazard in Bengkulu Province has not been assessed province-wide, as previous studies covered only Bengkulu City and the national hazard map presents bedrock values. The M 6.0 earthquake of 23 May 2025, which damaged dozens of houses in Bengkulu City, underscores the need for a surface-level assessment. This study aims to analyze the seismic hazard level in Bengkulu Province using the Probabilistic Seismic Hazard Analysis (PSHA) method and deaggregation analysis to identify dominant earthquake sources. The data used include earthquake catalogs from 1906–2024 provided by USGS and BMKG within a 500 km radius of the study area, as well as Vs30 data to account for local site effects. PSHA calculations were conducted for two exceedance probability scenarios: 10% in 50 years (return period of 475 years) and 2% in 50 years (return period of 2,475 years). The results show that surface Peak Ground Acceleration (PGA) values range from 0.39–1.45 g for the 475-year return period and 0.60–1.94 g for the 2,475-year return period, with the highest values concentrated along the Musi–Ketaun segment of the Great Sumatra Fault. Deaggregation results indicate that short return-period hazards have a dominant contribution from nearby active faults (≈15 km, Mw 6.6), while long return-period PGA contributions shift to distant megathrust sources (≈65 km, Mw 8.6). These findings provide crucial information for earthquake-resistant building design and disaster mitigation planning in Bengkulu Province.