RE-EVALUATION OF SEISMIC HAZARD IN TASIKMALAYA CITY USING PROBABILISTIC APPROACH

Abstract

Tasikmalaya is one of the earthquake-prone cities in Indonesia as a result of collision of the
Indo-Australian and the Eurasian plate. Earthquake mitigation efforts are needed to reduce the impact of future
earthquakes. One of the mitigation efforts that can be proposed is a re-evaluation of the seismic hazard of the
city. The main objective of this study was to re-evaluate seismic hazard expressed in Peak Ground Acceleration
(PGA) and spectral acceleration at bedrock level based on a probabilistic approach, particularly in Tasikmalaya
City. We first processed the earthquake data then adopted the new 22 seismogenic structures as the earthquake
sources. Furthermore, we determined the characterization of each earthquake sources, selected, and adjusted
the ground motion attenuation, and logic tree processed to manage the uncertainty of earthquake recurrence,
magnitude distribution, and ground motion attenuation. Using Probabilistic Seismic Hazard Analysis (PSHA),
PGA and spectral acceleration at bedrock level corresponding to 2% exceedance of 50 years’ probability were
calculated. The seismic hazards were quantified in terms of PGA and spectral acceleration at two fundamental
periods of 0.2 and 1.0 s. The results showed that the subduction interface zones in southern Java and
background seismicity significantly contributed to the seismic hazard in Tasikmalaya City. If compared with
the 2010 Indonesian earthquake hazard maps, the results have relatively higher values in the three hazard maps
which might due to the different characterization of earthquake sources, earthquake catalogs, and the GMPE
to be used.