Slip distribution effect in spatial coulomb stress analysis (Case study: Palu earthquake on September 28, 2018)

Abstract

On September 28, 2018, the Palu-Koro fault released the accumulated stress that caused the earthquake. An earthquake with magnitude 7.5 caused large and massive damage around Palu. There were many aftershocks along the Palu-Koro fault. This research aims to calculate a model of spatial Coulomb stress based on this event to find a correlation between mainshock and the aftershocks. The slip distribution was used as an input of the spatial stress Coulomb modeling to increase the accuracy. We use the Teleseismic Body-Wave Inversion method to calculate slip distribution along the fault plane. As a result, this earthquake was generated by the Palu-Koro fault movement with Mw 7.48, strike 350°, dip angle 67°, and rake -9°. There are three asperity zones along the fault plane located in the north and southern parts of the fault plane. The location of the most energy discharge is in the south asperity zone of the fault plane model with a maximum slip value of 1.65 meters. The spatial Coulomb stress change of this event shows that aftershocks concentration are in areas experiencing increased stress after the earthquake.

Seismic Deformation Analysis of the 28th September 2018 Palu Earthquake (7.5 Mw) Using InaCORS Station Data and Okada Model

“…The earthquake parameters include a depth of 8 km, a dip angle of 65˚, a strike of 351˚, and a rake of -46˚. Spatial Coulomb Stress analysis in previous research obtained earthquake parameters with a magnitude of Mw 7.48, strike 350˚, dip angle of 67˚, and rake of -9˚, with a maximum slip of 1.65 meters (Wulur et al, 2021). Meanwhile, using Inversion Teleseismic Body waves, earthquake parameters were found to be a strike of 353˚ ± 5˚, dip of 65˚ ± 5˚, rake of -4˚ ± 5˚, with dimensions of 150 km by 45 km and a slip of 1.5 meters (Yolsal-Çevikbilen & Taymaz, 2019).…”