The Khorat plateau covers most of northeast Thailand along with parts of southern Laos. Recent earthquake hazard assessment and other studies of the regional Thakek fault have rarely appeared in publications and reports. The Thakek fault zone in the Laos region includes three main principal fault planes, but it rapidly fades out when the fault passes through Thailand. A geophysical hidden fault study in the Khorat plateau is herein performed in Bung Kan and Nakhon Phanom provinces, Thailand, where the surface expression is difficult to document through conventional geological surveys. Some fault traces have been identified by satellite image interpretation and digital elevation model analysis. Geological field investigation and electrical resistivity tomography surveys were carried out in order to determine an optimal site for trenching. The electrical resistivity tomography results show zones of high and low resistivity interpreted as coarse sediment layers and mudstone, respectively. The maximum vertical fault offset occurring along the fault trace interpreted from the three-dimensional electrical resistivity tomographic slices is 40 ± 5 m. Based on the electrical resistivity tomography results, a trench was excavated to directly investigate patterns of faulting and deformation. Based on structural geological observations at the trench wall, indications of faulting have been tentatively identified. In particular, faulting appears to have displaced mudstone over Quaternary sediments with vertical offsets >3.5 m cutting the youngest unit. The result has implications for seismic hazard assessment in northeast Thailand.

中文翻译：

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泰国东北部隐藏的 Thakek 断层的电阻率层析成像检测

呵叻高原覆盖了泰国东北部的大部分地区以及老挝南部的部分地区。最近关于区域 Thakek 断层的地震灾害评估和其他研究很少出现在出版物和报告中。老挝地区的Thakek断层带包括三个主要断层面，但当断层穿过泰国时迅速消失。本文在泰国的 Bung Kan 和 Nakhon Phanom 省进行了 Khorat 高原的地球物理隐藏断层研究，这些地区的表面表达难以通过常规地质调查记录。通过卫星图像解译和数字高程模型分析，已经确定了一些断层痕迹。进行了地质实地调查和电阻率层析成像调查，以确定挖沟的最佳地点。电阻率层析成像结果显示高电阻率和低电阻率区分别被解释为粗沉积层和泥岩。从三维电阻率层析切片解释的断层轨迹上发生的最大垂直断层偏移为 40 ± 5 m。根据电阻率层析成像结果，挖掘了一条沟渠以直接研究断层和变形的模式。根据沟壁构造地质观察，初步确定了断层迹象。特别是，断层作用似乎已经取代了第四纪沉积物上的泥岩，垂直偏移大于 3.5 m，切割了最年轻的单元。该结果对泰国东北部的地震灾害评估具有重要意义。