Mapping Earthquake Prone Areas Using a Probabilistic Seismic Hazard Analysis (PSHA) Approach in South Malang Area

Abstract Geologically, Indonesia is situated at the convergence of major global tectonic plates, namely the Indo-Australian, Eurasian, and Pacific plates, making it a country with a significantly high earthquake risk. In 2021, a 6.1 Mw earthquake occurred, followed by 16 aftershocks within a span of 3 days. This earthquake struck near the southern coast of East Java, specifically in the Malang Regency area. The geological structure of this coastal region is predominantly composed of swamp sediment and limestone from the Wonosari formation. These geological conditions result in significant ground displacement during an earthquake. Based on seismic and soil conditions, the southern coastal region of Malang is identified as a high-risk area for large-scale earthquakes. Therefore, a Probabilistic Seismic Hazard Analysis (PSHA) approach is essential to assess earthquake hazard levels as a foundation for earthquake disaster mitigation efforts. The required data includes real-time earthquake data, consisting of the time of occurrence, depth, magnitude, and location of the earthquake. From this PSHA approach, variations in Peak Ground Acceleration (PGA) are produces a range from 49.3415 gal to 86.6479 gal for a 10% probability of exceedance and from 56.70847 gal to 100.16678 gal for a 2% probability of exceedance. Based on the PGA values, Gedangan, Sumbermanjing Wetan, Tirtoyudo, and Ampelgading District are the district with the highest PGA value for both probabilities. Pagak and Pagelaran District has a lower PGA value for both probabilities when compared to Sumbermanjing Wetan District. The PGA values can produce for creating a land vulnerability map. Through this map, the risk of earthquake hazards can be analyzed, enabling effective disaster mitigation strategies to reduce the risk of material damage and casualties when an earthquake occurs.