Sulawesi Island is located at the triple junction between the converging Australian, Sunda, and Philippine plates. The magnitude (Mw) 7.5 Palu earthquake occurred on 28 September 2018 on Sulawesi Island and caused serious casualties. The causative fault of the Palu earthquake was the left-lateral, strike-slip Palu-Koro fault, which has a rapid slip rate. We experienced this earthquake in Palu City and conducted field investigations on coseismic surface ruptures 1 d after the earthquake. Field surveys revealed that the coseismic surface ruptures were characterized by left-lateral offset, en echelon tensional cracks, mole tracks within a narrow zone, and large areas of sand liquefaction that increased the damage and losses. We measured the coseismic displacements along surface ruptures and observed a maximum coseismic offset of ∼6.2 m. The rupture traces in the north Palu Basin near Palu City mark the previously unmapped Palu-Koro fault. Based on the field investigations, we determined the exact location of the Palu-Koro fault within the Palu Basin and found that the Palu-Koro fault zone can be divided into three branches: F1, F2, and F3, forming a typical flower structure.

中文翻译：

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印度尼西亚苏拉威西岛2018年Mw 7.5帕卢地震中的同震表面破裂

苏拉威西岛位于澳大利亚，Sun达和菲律宾板块交汇处的三重交界处。苏拉威西岛于2018年9月28日发生了7.5级帕卢大地震，造成严重人员伤亡。帕卢地震的原因断层是左侧走滑的帕卢－科罗断层，滑移速率很快。我们在帕卢市经历了这次地震，并在地震发生1天后对同震表面破裂进行了现场调查。现场调查显示，同震表面破裂的特征是左侧偏移，梯形张拉裂缝，狭窄区域内的葡萄胎痕迹以及大面积的砂土液化，从而增加了破坏和损失。我们测量了沿表面破裂的同震位移，并观察到最大同震偏移量约为6.2 m。帕卢市北部帕卢盆地北部的破裂痕迹标志着先前未测绘的帕卢－科罗断裂。在野外调查的基础上，我们确定了帕卢盆地内帕卢科罗断层的确切位置，发现帕卢科罗断层带可分为三个分支：F1，F2和F3，形成典型的花型结构。