Earthquake Risk Potential Caused by Active Faults in Sumatra (Case Study: Earthquakes in the Land of West Sumatra Province and its vicinity)

Abstract

The land of West Sumatra province is one of prone area stricken by the destructive earthquakes. Based on historical records, the land of West Sumatra province has a high seismic risk related to the earthquake events along active faults, such as the Sianok, Barumun, Sumani, Siulak and Angkola faults. Some destructive earthquakes occurred in these faults and caused fatalities in West Sumatra area and its vicinity, e.g., the earthquakes near Bukit Tinggi district in 1926, 1977, 2007 (doublet earthquakes-Tabel 1) and 2022. A previous study shows that the Sumani, Siulak, Sianok, Barumun and Angkola faults has a potential magnitude 7.1-7.7, a geodetic slip-rate of 6-14 mm/y respectively and these move generally strike slip. Using these magnitude scenarios to make the earthquakes impact modelled, we find the maximum intensity is about of VII-VIII MMI scale, the Peak Ground Acceleration (PGA) is about of 42-64 % g, and Peak Ground Velocity (PGV) is about of 30-50 cm/s for the assumption of 5-15 km hypocentral depth. Also with using the scaling law relation of earthquake parameters and magnitude scenarios the earthquake return period can be calculated by a kinematic model with the source mechanism was modelled as a strike slip faults. Estimation of the earthquake return period with magnitude (Mw) scenarios about 7.1-7.7 for these active faults is about of 114 until 612 years for strike slip model respectively. This method can be developed to make identically assessment for others active fault in Sumatra region and the result can be used as one of a consideration to support of planning of the long term landscape in the prone of earthquakes area.