Impact of rupture complexity on seismic hazard: Case of the 2018 M_w7.5 Palu earthquake

Abstract. Rupture complexity results in difficulty with quantifying seismic hazards, such as the probability of an earthquake on multiple segments in an active fault system and spatial distribution of the fault displacement on the surface. Here we propose a dynamic model to explain rupture complexity. To confirm this model’s credibility, we used it to explain the rupture behavior of the 2018 M_w7.5 Palu earthquake, which splayed along several sub-fault planes on the surface. The Palu event initiated on an unidentified fault and propagated on a curved plane on the Palu-Koro and Matano faults. According to the Interferometric Synthetic Aperture Radar data, both principal (on-fault) and distributed (off-fault) faulting were identified, and spatial displacement on the surface could be evaluated. To model the complex geometry of the coseismic rupture plane and corresponding deformation, we proposed a dynamic model through the discrete element method. Our model demonstrated rupture along a planar fault at depth and several splay faultings with various deformation on the surface, corresponding to the observations. The simulations represented temporal rupture behavior that covers several earthquake cycles and probability of superficial fault displacement that shed light on subsequent seismic hazard assessment and probabilistic fault displacement hazard analysis, respectively.