Seismic Microzonation Using the Deterministic Seismic Hazard Analysis (DSHA) Method to Identify Earthquake Vulnerability in Ulu Belu Subdistrict of Tanggamus Regency

Abstract The central government is required to have more detailed spatial planning in the Ulu Belu sub-district based on the regulation of the Minister of Agrarian Affairs and Spatial Planning/National Land Agency Number 11 of 2021 contained in the Regional Spatial Plan of Tanggamus Regency. The region has a considerable investment potential estimated at 5 trillion Rupiah. However, earthquake disasters often cause significant damages to the infrastructure and buildings and also serve as a platform for the occurrence of other calamities. The map on earthquake-prone areas in Lampung Province also categorizes Ulu Belu sub-district as highly vulnerable. Therefore, there is a need for a comprehensive earthquake hazard microzonation study. This was achieved through earthquake hazard assessment using the Deterministic Seismic Hazard Analysis (DSHA) method which was used to determine the peak value of acceleration at the bedrock. Furthermore, a Site-Specific Analysis (SSA) was adopted to predict PGA values on the surface with a focus on the East Semangko Fault located about 12 km from the Ulu Belu sub-district and a maximum magnitude of M7.1. It was observed that the class of sites in the region varied between soft soil (SE) and rock (SB). The DSHA analysis results also showed that the PGA bedrock varied between 0.08 and 0.53 g. Meanwhile, the distribution of surface PGA values ranged from 0.10 to 0.87 g, leading to the classification of the area as MMI VI to XXI scale. The shaking of soil at this intensity was believed to have the capacity to cause damage ranging from mild to severe.