High-resolution probabilistic seismic hazard analysis of West Nusa Tenggara, Indonesia

Abstract

The interest to build a nuclear power plant in West Nusa Tenggara Province has caused a concern related to the seismic hazard. One of the challenges was that the existing low-resolution national seismic hazard map did not cover the entire islands of West Nusa Tenggara Province. In this paper, preliminary probabilistic seismic hazard analysis of West Nusa Tenggara was performed to complement the existing national seismic hazard map for West Nusa Tenggara. The analysis was carried out using OQ software based on the seismotectonic model and GMPE developed by PUSGEN. Similar seismotectonic model and seismic event trees were implemented using a finer grid spacing of 500–1000 m. The seismotectonic model included active shallow crustal, subduction interface, and background sources with a total number of 50 seismogenic sources and was calculated using 108 GMPE paths. Two hazard levels were considered, each representing 1% and 2% POE in a 100-year return period. A comparison to the existing national seismic hazard map on the PGA level has been presented in this study and yielded a 13–25% difference in the ground acceleration value. Spectral hazard maps representing the shorter period (0.2 s) showed a maximum ground acceleration value of more than 2 g, especially in the northern part of Sumbawa Island. Beyond the longer spectral period (1 s), ground acceleration gradually decreases to the level below the PGA level.