Sulawesi Island, located in eastern Indonesia, lies at the triple junction of the Australian, Sunda, and Philippine Sea plates. It exhibits a distinctive K-shape, with each arm having undergone independent geological evolution. Driven by the latest Miocene collision (∼5 Ma) between the Banggai-Sula microcontinent and the East Arm, the deformation is accommodated by the corresponding motion of individual blocks at various locations, resulting in specific patterns of seismic moment release. In this study, we investigate the distributions of shallow earthquakes (< 60 km) based on the ISC-EHB and BMKG catalogs, as well as the focal mechanisms based on the GCMT catalog, to study the seismotectonics of Sulawesi. The results are grouped into five regions with characteristic seismic patterns well corresponding to tectonic signatures and geodetic observations. The main findings can be summarized in two parts. First, thrust earthquakes release seismic energy due to oceanic plate subduction, including, in order of moment release, those along the North Sulawesi Trench to the north, the Makassar Strait Thrust to the west, and the Tolo and Buton Thrust to the southeast. Notably, there is a seismic gap near the center of the North Arm that may indicate potential risk for damaging earthquakes, while those of the Batui Thrust are only minor. The second part involves left-lateral strike-slip motions along the Central Sulawesi Fault System. The occurrence of the 2018 Mw 7.6 Palu earthquake not only filled the gap of seismic deficiency on the Palu-Koro fault but also triggered overall seismic activity in Sulawesi. Additionally, note the low seismicity on the segment offshore northwest Sulawesi, which may be beyond the high relative motion between the Makassar and North Sula Block.

中文翻译：

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印度尼西亚苏拉威西岛地震构造


苏拉威西岛位于印度尼西亚东部，位于澳大利亚海板块、巽他海板块和菲律宾海板块的三重交界处。它呈现出独特的K形，每条臂都经历了独立的地质演化。在邦盖-苏拉微大陆和东臂之间最近的中新世碰撞（∼5Ma）的驱动下，不同位置的各个块体的相应运动适应了变形，从而产生了特定的地震矩释放模式。在本研究中，我们基于ISC-EHB和BMKG目录调查浅层地震（<60公里）的分布，以及基于GCMT目录的震源机制，以研究苏拉威西岛的地震构造。结果分为五个区域，其特征地震模式与构造特征和大地测量观测很好地对应。主要发现可概括为两部分。首先，逆冲地震因大洋板块俯冲而释放地震能量，按释放时刻的顺序，包括北苏拉威西海沟沿线的地震、西边的望加锡海峡逆冲地震、以及东南部的吐露港和布顿逆冲地震。值得注意的是，北臂中心附近存在一个地震间隙，这可能表明存在发生破坏性地震的潜在风险，而巴图伊逆冲断层的地震风险较小。第二部分涉及沿中苏拉威西断层系的左旋走滑运动。 2018年帕鲁7.6级地震的发生，不仅填补了帕鲁-科罗断裂带地震的空白，还引发了苏拉威西岛的整体地震活动。此外，请注意苏拉威西岛西北近海部分的低地震活动，这可能超出了望加锡和北苏拉地块之间的高相对运动范围。