Earthquake Risk Area Mapping Based on Probabilistic Seismic Hazard Analysis (PSHA) Method and Microtremor Data in Nias Island

Abstract

Mapping seismic hazards have been done using Probabilistic Seismic Hazard Analysis (PSHA) and microtremor in Nias Island. This research was purposed to determine seismic Hazards based on peak ground acceleration distribution using software Ez-Frisk 7.52 and the results of microtremor data single station on ten measuring points processed using software geophys. The result of the calculation PSHA value from all sources of the earthquake (Megathrust, Fault, Background, and Local fault Mentawai) obtained distribution hazard value in PGA condition for the return period of 500 years and 2500 years at the base rock with values ranging between 1.0 g-1.5 g and 1.0 g-1.5 g. While for hazard value in spectral condition T = 0.2 seconds for the return period of 500 years and 2500 years with the value ranging between 3.0 g-3.5 g and 6.0 g-8.0 g. For hazard value in spectral condition T=1.0 second for the return value of 500 years and 2500 years with the value ranging between 1.0 g-1.5 g and 2.0 g-2.5 g. The result of processing microtremor shows that North of Nias has local geology characteristics with a dominant frequency range between (0.89-6.81) Hz, amplification value between 0.54-1.92, index seismic susceptibility value between 0.13-4.14, the value of surface peak ground acceleration (0.65-185) g, the value of bedrock peak ground acceleration (0.16-0.19) g and, thickness of weathering layer between (12.3-96) m, the value of ground shear strain 1.5 × 10 −5-73 × 10 −5. Informasi Artikel Abstrak Proses artikel: