Three-dimensional Slope Stability Evaluation Under Seismic Load: A Case Study in Balaroa, Central Sulawesi, Indonesia

The 2018 Mw 7.4 Palu earthquake was one of the largest natural disasters in Indonesia's history. This catastrophic event was followed by massive mass movements in the Balaroa area, leading to extensive damage to infrastructure and a huge loss of life. A three-dimensional slope stability analysis under seismic conditions emerged as one of the effective solutions for preventing and mitigating the impact of mass movement disasters triggered by earthquakes, particularly in large areas. The objective of this study is to evaluate the map results of the factor of safety (FoS) with the actual massive mass movement that occurred during the 2018 Mw 7.4 Palu earthquake. The research methodology is a three-dimensional stability analysis under non-seismic and seismic conditions with a seismic load coefficient (Kh) under the 2018 Mw 7.4 Palu earthquake using Plaxis 3D LE. The input variables used in this research are the study area 3D modelling, soil parameters, and the seismic load coefficient. The 3D slope stability analysis results show that the FoS map under non seismic condition with FoS values of 2.07 to 4.46, and the results under the 2018 Mw 7.4 Palu earthquake have FoS 0.66-0.90. This evaluation is based on the comparison between the analysis result with the actual massive mass movement under the 2018 Mw 7.4 Palu earthquake condition. This analysis results in an area relatively consistent with the actual mass movement in the study area. It can be interpreted that the massive landslide that occurred in the study area was significantly influenced by the Mw 7.4 Palu earthquake event on 28 September, 2018.