Multi-archive record of late Quaternary paleoseismicity along the surface projection of the 2017 Pohang earthquake seismogenic fault, SE Korea

IF 1 4区 地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY
Seongjun Lee, Jong-Won Han, Sangmin Ha, Jeong-Heon Choi, Yeong Bae Seong, Tae-Ho Lee, Hee-Cheol Kang, Moon Son
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Abstract

The 2017 Pohang earthquake (ML 5.4) ranks as the second-largest instrumental earthquake in the Korean Peninsula and the country’s most destructive seismic event. The earthquake history of the Pohang area prior to the 2017 event is unknown due to the absence of instrumental seismic activity and the lack of mapped Quaternary faults near the 2017 epicenter. The aim of the present study is to identify evidence for previous earthquake ruptures along the surface projection of the seismogenic fault and interpret their paleoseismic implications. The study involved comprehensive paleoseismological investigation, including geomorphic analysis, field-work, drillhole surveys, trench excavation, and numerical age dating. Geomorphic analysis and drillhole surveys revealed two lineaments presumed to have originated from Quaternary faulting: NNE-SSW-striking Fault-1 and NE-SW to NNE-SSW-striking Fault-2. At the excavation site of Fault-1, which is regarded as the seismogenic fault of the 2017 Pohang earthquake, stratigraphic features and numerical ages show that the penultimate event occurred between 11 ± 1 and 2.6 ± 0.1 ka and that the most recent event took place after 0.17 ± 0.01 ka. Combined results from two outcrops of Fault-2 give occurrence ages for the penultimate and most recent events of ca. 200 ka and between 148 ± 7 ka and the analytical limit of 14C dating (> 43,500 BP), respectively. Our findings reveal that at least three seismic events causing surface ruptures have occurred in the Pohang area during the late Quaternary before the 2017 Pohang earthquake.

沿 2017 年韩国东南部浦项地震发震断层地表投影的第四纪晚期古地震多档案记录
2017 年浦项地震(ML 5.4)是朝鲜半岛第二大工具性地震,也是朝鲜最具破坏性的地震事件。由于 2017 年震中附近没有器震活动,也没有绘制第四纪断层图,因此 2017 年地震之前浦项地区的地震历史尚不清楚。本研究的目的是确定沿发震断层地表投影以往地震断裂的证据,并解释其对古地震的影响。研究涉及全面的古地震学调查,包括地貌分析、野外工作、钻孔勘测、沟槽挖掘和数值年代测定。地貌分析和钻孔勘测揭示了两条推测源于第四纪断层的线状构造:NNE-SSW 走向的断层-1 和 NNE-SSW 至 NNE-SSW 走向的断层-2。断层-1 被认为是 2017 年浦项地震的发震断层,在断层-1 的发掘现场,地层特征和数值年龄显示,倒数第二次事件发生在 11 ± 1 ka 到 2.6 ± 0.1 ka 之间,最近一次事件发生在 0.17 ± 0.01 ka 之后。根据断层-2 两个露头的综合结果,倒数第二和最近事件的发生年龄分别为约 200 ka 和 148 ± 7 ka 与 14C 测定的分析极限(> 43,500 BP)之间。我们的研究结果表明,在 2017 年浦项地震之前的第四纪晚期,浦项地区至少发生过三次导致地表断裂的地震事件。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Geosciences Journal
Geosciences Journal 地学-地球科学综合
CiteScore
2.70
自引率
8.30%
发文量
33
审稿时长
6 months
期刊介绍: Geosciences Journal opens a new era for the publication of geoscientific research articles in English, covering geology, geophysics, geochemistry, paleontology, structural geology, mineralogy, petrology, stratigraphy, sedimentology, environmental geology, economic geology, petroleum geology, hydrogeology, remote sensing and planetary geology.
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