ABSTRACT
September 28, 2018, Sulawesi Earthquake of MW 7.5 is known to be caused due to a strike-Slip along the NNW-SSE trending Palu-Koro fault. Around 150 aftershocks were associated with the mainshock. In this paper, we consider 6 aftershocks MW 5 earthquake and investigate whether these were caused as a result of positive Coulomb stress changes on receiver fault (the fault on which the aftershock acts). To generate a fault model of the Palu-Koro fault from focal mechanism solutions of the mainshock event as listed in global CMT catalogue are used. The Coulomb failure stress change on both the nodal planes of the focal mechanism are computed and the Coulomb failure stress change imparted by the MW 7.5 mainshock on subsequent aftershocks with the epicentre location of each aftershock are compared. In addition, shear stress and normal stress changes are also computed. Coulomb stress changes for the 6 aftershocks range from −0.454 to 0.036 bar. Only 2 computational results (around 17%) are positive, all others (10 in number) are negative. Here we find that a vast majority of MW ≥5 aftershocks occurred in regions of negative Coulomb stress areas triggered by the MW7.5 mainshock. Thus, our results suggest that Coulomb stress changes did not contribute to the development of MW 7.5 sequence of earthquakes.
