PSHA-based earthquake vulnerability mapping in the Nias Islands, Indonesia

Abstract

Nias Islands is an area that is classified as prone to earthquakes. The location of the Nias Islands region on the ring of fire and subduction line which continues to move per year is the cause of the prone earthquake. This is evidenced by the record of earthquakes that occurred in the Nias Islands recorded as many as 7,152 events with a range of magnitude strength> 4 Mw from 1910 to 2022 for a 500-year return period. To determine the level of earthquake vulnerability in the Nias Islands region, earthquake vulnerability mapping is carried out using the PSHA (Probabilistic Seismic Hazard Analysis) method to calculate the value of peak ground acceleration.  This research begins by collecting earthquake sources in the research area in the IRIS and BMKG catalogs. The earthquake data was then converted from magnitude to Mw (magnitude moment), then de-clustered to get the main earthquake from all earthquake data. Then the a-value and b-value are searched to get the background earthquake source, then PSHA processing is carried out which results in the value of spectral acceleration for each predetermined grid. From the processing results, the PGA T=0s value is <0.05 g to 1.2 g, for PGA T=0.2s value is 1 g to 1.2 g and for PGA T=1s value is 0.4 g to 0.5 g.