In seismic hazard assessment, subsurface geophysical surveying has gained popularity in recent years towards fault mapping and determining seismic deformation parameters such as fault offset, recurrence, and depth of fault, locating proper trench sites based on the subsurface information. In the present study, electrical resistivity tomography (ERT) was used to (1) locate the trace of the southern segment of the Ulsan fault, (2) to test the applicability of ERT techniques for active fault mapping in a close to the highly urbanized and complex geological environment with a slow tectonic activity. We have applied the ERT technique at five sites. At one place, we used the Wenner array, Schlumberger array, Dipole-Dipole array, and Seismic-profiling techniques to know which method provides a better result in complex geological conditions like Korea. Out of these methods, the Dipole-Dipole array provided high-resolution results and was used for the other two sites. The ERT result shows high and low resistivity zones interpreted as bedrock (mainly Tertiary and Cretaceous formations) and coarse fluvial sediment layer, respectively. The maximum vertical displacement recorded along the fault varies from 6 m to 12 m. Based on the ERT results, two trenches were excavated to directly investigate the deformation pattern associated with the southern segment of the Ulsan fault. The ERT and trench survey results support that the southern Ulsan fault has slipped multiple times since Quaternary. Using this multi-approach, ~5 km long active fault map was prepared for the southern Ulsan Fault. It is found from this study that the integrated approach is highly beneficial where contrasting sub-lithological units exist in terms of their physical properties, even though human activity or the ongoing urbanization process has modified the surface morphology. This study argues for judicious use of ERT techniques to delineate the shallow subsurface geology across various active faults in the Korean peninsula and similar tectonic settings.

在地震危险性评估中，近年来，地下地球物理测量在断层测绘和确定地震变形参数（如断层偏移、重现和断层深度）方面得到了普及，并根据地下信息定位适当的沟槽位置。在本研究中，电阻率断层扫描 (ERT) 用于 (1) 定位蔚山断层南段的轨迹，(2) 测试 ERT 技术在靠近高度城市化地区的活动断层测绘中的适用性地质环境复杂，构造活动缓慢。我们在五个地点应用了 ERT 技术。在一个地方，我们使用 Wenner 阵列、Schlumberger 阵列、Dipole-Dipole 阵列和地震剖面技术来了解哪种方法在韩国等复杂地质条件下提供更好的结果。在这些方法中，偶极-偶极阵列提供了高分辨率结果，并用于其他两个站点。ERT 结果显示，高电阻率区和低电阻率区分别被解释为基岩（主要是第三纪和白垩纪地层）和粗大的河流沉积层。沿断层记录的最大垂直位移从 6 m 到 12 m 不等。根据 ERT 结果，挖掘了两个沟槽，以直接研究与蔚山断层南段相关的变形模式。ERT 和海沟调查结果支持蔚山南部断层自第四纪以来多次滑动。使用这种多方法，为蔚山断层南部准备了约 5 公里长的活动断层图。从这项研究中发现，即使人类活动或正在进行的城市化进程已经改变了地表形态，在存在对比的亚岩性单元的物理特性的情况下，综合方法是非常有益的。本研究主张明智地使用 ERT 技术来描绘朝鲜半岛各种活动断层和类似构造环境中的浅层地下地质。