| Summary: | On May 29, 2017, the MW6.6 Poso earthquake occurred in Central Sulawesi, Indonesia, causing moderate damages. The mainshock rupture and primary aftershock cluster occurred in the active Palolo-Sausu tectonic zone, and some aftershocks also took place around the Tokararu fault. However, the rupture mechanism of this earthquake and its relation to regional tectonics are not clear. In this study, the rupture process of the Poso mainshock is estimated by finite-fault waveform inversion, which is constrained by teleseismic bodies and surface waves. The rupture propagates upward unilaterally in a southwest-dipping moderate-angle (∼34°) normal fault beneath Tokorondo Mountains, with a notable ∼15% initial moment release at the first 4s of the ∼12s rupture duration. The average and peak slip are 0.5 m and 1.5 m, respectively. The rupture velocity is relatively slow (less than 2.5 km/s), and the Coulomb stress changes due to the mainshock are obtained using the inverted coseismic slip.
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