KAJIAN BAHAYA TSUNAMI DI WILAYAH PESISIR KOTA DENPASAR MENGGUNAKAN PEMODELAN NUMERIK

Abstract

Bali Island has a high vulnerability to earthquakes and tsunamis due to its location between three major tectonic zones: the Flores Back Arc Thrust, the Lombok Strait Strike-Slip Fault, and the Sumba Megathrust. One of the high-risk areas is the southern coast of Bali, including Denpasar City, which has the potential to experience a Megathrust earthquake with a maximum magnitude of Mw 8.5. As the economic and administrative center of Bali, Denpasar City has a high population density and geographical conditions that increase the risk of tsunami impacts. This study aims to provide information on tsunami inundation heights and tsunami arrival times using the Cornell Multi-grid Coupled Tsunami model version 1.7 (COMCOT v1.7). The research was conducted in three stages: pre-modeling (processing bathymetric, topographic, and earthquake source data), tsunami modeling (using earthquake scenarios of Mw 8.0 and Mw 8.5), and post-modeling (analysis of tsunami arrival time and spatial analysis of flowdepth). The simulation results indicate that the Mw 8.5 scenario generates higher tsunami waves (4.79–7.42 m) and wider inundation coverage (294,100 ha or 23.01% of the Denpasar area) compared to the Mw 8.0 scenario. The earliest tsunami arrival occurs along the eastern coast of Serangan Village, approximately 21 minutes after the earthquake. Coastal areas are predominantly inundated by 3–6 m of water, with limited areas experiencing inundation exceeding 9 m. The Mw 8.5 scenario shows more severe impacts and shorter evacuation times. Therefore, more comprehensive mitigation strategies are required, including the provision of vertical evacuation facilities and the implementation of risk-based spatial planning.