Localization and characterization of the southern Ulsan fault (UF) using geo-electrical imaging: Implication for seismic hazard assessment in an urbanized area

IF 2.1 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Journal of Geodynamics Pub Date : 2022-05-01 DOI:10.1016/j.jog.2022.101919
Sambit Prasanajit Naik , Ohsang Gwon , Kiwoong Park , Sang Yeol Bae , Hyeon-Cho Shin , Jeong-Heon Choi , Young-Seog Kim
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引用次数: 3

Abstract

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.

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利用地电成像定位和表征蔚山南部断层(UF):对城市化地区地震危险性评估的启示
近年来,在地震危险性评估中,地下地球物理测量在断层制图和确定地震变形参数(如断层偏移量、复发性和断层深度)以及根据地下信息定位合适的沟位方面得到了广泛的应用。在本研究中,利用电阻率层析成像(ERT)(1)定位了蔚山断层南段的轨迹,(2)在接近高度城市化和复杂地质环境,构造活动缓慢的情况下,测试了ERT技术在活动断层填图中的适用性。我们在五个地点应用了ERT技术。在一个地方,我们使用了Wenner阵列、Schlumberger阵列、偶极-偶极阵列和地震剖面技术,以了解哪种方法在韩国等复杂地质条件下能提供更好的结果。在这些方法中,偶极子-偶极子阵列提供了高分辨率的结果,并用于其他两个地点。ERT结果显示,高电阻率带和低电阻率带分别被解释为基岩(主要是第三纪和白垩纪地层)和粗河流沉积层。沿断层记录的最大垂直位移在6米到12米之间。在ERT结果的基础上,挖掘了两条沟,直接研究了与蔚山断层南段相关的变形模式。ERT和海沟测量结果支持了第四纪以来蔚山南部断层多次滑动的观点。利用这种方法,绘制了蔚山断裂带南部约5 km长的活动断裂带图。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,在存在不同亚岩性单元的物理性质方面,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和类似构造环境中各种活动断层的浅层地下地质。
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来源期刊
Journal of Geodynamics
Journal of Geodynamics 地学-地球化学与地球物理
CiteScore
4.60
自引率
0.00%
发文量
21
审稿时长
6-12 weeks
期刊介绍: The Journal of Geodynamics is an international and interdisciplinary forum for the publication of results and discussions of solid earth research in geodetic, geophysical, geological and geochemical geodynamics, with special emphasis on the large scale processes involved.
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