Seismicity of Batubesi Dam at Sorowako Region Based on Earthquake Data and Microtremor Measurement

Batubesi Dam which is located in Sorowako region in the middle part of Sulawesi island had been designed with seismic coefficient about 0.20g. The region constitutes an active earthquake zone with the recurrence frequency and magnitude of the earthquake are relatively high. The region is located on and active fault zone due to lateral fault movement (strike-slip) of Matano fault, Palukoro fault, and Walanea fault that categorized as shallow crustal earthquakes. To recognize characteristic of the earthquake at the site of interest, the historical earthquakes (background) data surrounding the study area and local microtremor measurements data are analyzed by means of a probabilistic seismic hazard analysis (PSHA) and deterministic seismic hazard analysis (DSHA) using some ground-motion models in attenuation relationship equations in resulting of seismic hazard parameter as represented by peak ground acceleration (PGA) values in earthquake scenario at operating basis earthquake (OBE), maximum design earthquake (MDE), and maximum credible earthquake (MCE) conditions. The PGA value in OBE condition is about 0.35g, in MDE about 0.45g, and in MCE about 0.49g. These values are used as reference to evaluate compliance of the current technical aspects with the new required design facing the updated seismicity parameters.