The impact of Coulomb stress changes of the 2018 Mw 7.5 Palu earthquake, Indonesia

This paper studied the effects of Coulomb stress in understanding the proximity to failure on the Palu-Koro fault system.An earthquake occurred on a large strike-slip fault in the northern part of Sulawesi Island, Indonesia, on September 28, 2018.Coulomb stress increased by approximately 1 bar, corresponding closely to the locations of aftershocks and areas where stress dropped by more than 10 bars.Based on the focal mechanisms of the aftershocks and source models of the main shock, the Coulomb failure stress changes on both of the focal mechanism nodal planes are calculated.Additionally, we calculated the changes in Coulomb stress on the focal sources of each aftershock.Our stress model indicates a positive correlation within the areas of the extended Coulomb stress caused by the combination of seismic activities.We investigated the Coulomb stress as a possible origin for the aftershocks, which are most likely to slip optimally oriented for failure due to the local stress field generated by the mainshock.The Palu 7.5 earthquake led to the distribution of surface displacements.Moreover, calculated horizontal displacement increased in the NW-SW direction, ranging from 1 to 1.3 meters.The stress maps included in this paper are crucial in predicting the expected locations of future aftershocks and mitigating the potential for earthquakes.