Risk Earthquake Zone Analysis By Estimation Site Amplification at Surface In Badung Regency, Bali Using PSHA Method

The frequency of earthquakes in the southern of Bali Island was high. The earthquake source came from subduction of the Indo-Australian Plate with the Eurasian Plate in the south and the Flores back-arc thrust fault in the north caused earthquake activities. These activities caused Badung Regency to be vulnerable getting the impact of earthquakes in the form of damage. Risk earthquake in Badung Regency was analyzed in each sub-district to determine side effects and amplification. Firstly, risk earthquake zone analysis was carried out by calculating the Probabilistic Seismic Hazard Analysis (PSHA) of the probability of exceedance 2% in 50 years using the R-CRISIS 2020 software in bedrock. Then, the PSHA on the surface was calculated by adding the data from Vs30 USGS. The amplification value was calculated based on the comparison of the PSHA on the surface and bedrock. Results of the analysis showed that the PSHA ​​in bedrock and surface rocks in Badung Regency for peak ground acceleration (PGA) value were in the range 0. 41 – 0. 51 g. Meanwhile, spectral acceleration (SA) values at T = 0. 2 and T = 1 second respectively in the range of 0. 83 – 1. 08 g and 0. 29 – 0. 44 g. Overall sub-districts in Badung Regency are risk earthquake zone based on the amplification value. The zone that is relatively more risk earthquake when PGA is in the Petang District. The districts that are relatively more risk when SA at T = 0. 2 seconds are in the Districts of Mengwi, Abiansemal, and Petang. Meanwhile, SA at T = 1 second is relatively more risk in Kuta District, North Kuta, and parts of Mengwi.