ANALISIS PROBABILISTIK BENCANA TSUNAMI TERHADAP TINGKAT KERENTANAN BANGUNAN DI KOTA PAINAN, SUMATERA BARAT BERDASARKAN RASIO GEMPA BUMI DENGAN METODE LOGIC TREE

Abstract

West Sumatra, especially the Mentawai Megathrust segment, is a vulnerable segment where active faults collide, triggering earthquakes followed by tsunami disasters. The aim of this research is to determine the influence of different variables of seismic activity levels and ratios between large and small earthquakes using the Logic Tree tool, assess the tsunami hazard potential using Probabilistic Tsunami Hazard Assessment (PTHA), and identify buildings that can be used as evacuation centers based on the Building Tsunami Vulnerability (BTV) index in the Padang fault zone in Painan City. The simulation in this research utilized the Cornell Multi-grid Coupled program. From the simulation, calculations were conducted to determine the tsunami height for each building in Painan City, and the recurrence interval was determined using the PTHA equation. Additionally, the vulnerability level of buildings was determined using the BTV equation. The processed PTHA data revealed that the maximum tsunami height in a 1000-year recurrence interval is 5.664 meters, while in a 4000-year recurrence interval, it is 36 meters. Based on the Building Tsunami Vulnerability index, the recommended mitigation solution is to use buildings with BTV class values of 0 (none), 1 (low), and 2 (medium). For example, the Branch Office of Bank Nagari building, which is a 4-story reinforced concrete structure, it is designated for residents living near the coastline or far from the hills. Additionally, residents can utilize highlands or hills as evacuation areas.