The 7.5 Mw tectonic earthquake that hit Palu City on 28 September 2018 was followed by tsunami and liquefaction, triggered massive mudflows in Balaroa, Petobo, and Jono Oge areas. This study focuses on the generating factors of liquefaction such as the condition of soil lithology, depth of water table, the distance to the focal mechanism, and the thickness of soft sediment. Microtremor data, including the Horizontal Vertical Spectral Ratio (HVSR), geological condition, and borehole data, were examined to conduct the liquefaction analysis. The analysis results based on the microtremor data showed that the distribution of ground shear strain values in Palu City ranged from 0.75 × 10–4 to 2.56 × 10–4. The distribution of the locations of the liquefaction was correlated to the distribution of ground shear strain values. High ground shear strain values and a shallow groundwater level were discovered in Palu City valley, which indicates that liquefaction in Palu City will undoubtedly occur. The semi-empirical method confirmed that Balaroa, Petobo, and Jono Oge had undergone large-scale liquefaction at a maximum depth of 16 m below the ground level. The average peak of water runoff that generated the mudflow was estimated to be at 11.31 cm3/s. Since the soil has loose soil grain with high water content, the soil will turn into a massive amount of mud during the liquefaction.

中文翻译：

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帕卢的液化：大规模泥石流的原因

2018 年 9 月 28 日袭击帕卢市的 7.5 兆瓦构造地震之后发生了海啸和液化，在巴拉罗阿、佩托博和城诺奥格地区引发了大规模泥石流。本研究重点研究了土壤岩性条件、地下水位深度、与震源机制的距离、软质沉积物厚度等液化的产生因素。检查微震数据，包括水平垂直光谱比 (HVSR)、地质条件和钻孔数据，以进行液化分析。基于微震数据的分析结果表明，帕卢市地面剪应变值的分布范围为0.75×10-4～2.56×10-4。液化位置的分布与地面剪切应变值的分布相关。在帕卢市河谷发现了较高的地面剪切应变值和较浅的地下水位，这表明帕卢市无疑会发生液化。半经验方法证实，Balaroa、Petobo 和 Jono Oge 在地表以下最大深度 16 m 处发生了大规模液化。产生泥流的水径流平均峰值估计为 11.31 cm3/s。由于土壤中土粒疏松，含水量高，在液化过程中，土壤会变成大量的泥土。和城野大毛在地平面以下最大深度 16 m 处发生了大规模液化。产生泥流的水径流平均峰值估计为 11.31 cm3/s。由于土壤中土粒疏松，含水量高，在液化过程中，土壤会变成大量的泥土。和城野大毛在地平面以下最大深度 16 m 处发生了大规模液化。产生泥流的水径流平均峰值估计为 11.31 cm3/s。由于土壤中土粒疏松，含水量高，在液化过程中，土壤会变成大量的泥土。