Segmentation geometry of strike-slip fault systems in slow-deforming regions: a proposed method and case study of the Yangsan Fault, South Korea

IF 1 4区 地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY
Taehyung Kim, Jin-Hyuck Choi
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引用次数: 0

Abstract

Fault location and geometry are the most fundamental input data in seismic hazard analysis, the ultimate aim of which is to mitigate damage from future large earthquakes. In regions prone to large earthquakes or where cumulative deformation by multiple earthquake events are well expressed in the landscape, fault models are constructed primarily by (1) identifying active fault traces, mapped mostly by the surface ruptures associated with large earthquakes; (2) simplifying fault traces while capturing their geometrical characteristics; and (3) segmenting the simplified geometry, given that a single earthquake does not always rupture the entire length of a fault system. In slowly deforming regions, however, the construction of fault models is challenging, even though geologic records of large earthquakes exist, because of the lack of clear active fault traces. Indeed, surface-rupturing earthquakes may not be part of the historical periods owing to their long recurrence time of thousands of years or more. Nevertheless, seismic hazard analysis is required for densely populated and industrial areas in slowly deforming regions, such as South Korea. On the basis of criteria established previously for determining segmentation geometry in fault models, here we propose a methodology for identifying the segmentation geometry of strike-slip fault systems in slowly deforming regions. In terms of the criteria used to identify segment boundaries, we examine along-fault variations not only in fault geometry but also in fault-surrounding lithology and fault-related geomorphic features. We test the methodology for assessing the fault segmentation geometry in a case study of the Yangsan Fault, which is one of the most active seismogenic strike-slip faults on the Korean Peninsula. Results show that the ∼200 km length of the Yangsan Fault on land consists of 12 to 15 distinct fault segments. We discuss how models of fault segmentation geometry are able to improve seismic hazard analysis in regions that have not experienced surface-faulting earthquakes in historical period.

慢变形地区走向滑动断层系统的几何分割:一种拟议方法和韩国梁山断层案例研究
断层位置和几何形状是地震灾害分析中最基本的输入数据,其最终目的是减轻未来大地震造成的破坏。在容易发生大地震的地区,或多次地震的累积变形在地貌中表现明显的地区,断层模型主要通过以下方法构建:(1) 识别活动断层迹线,主要通过与大地震相关的地表断裂来绘制;(2) 简化断层迹线,同时捕捉其几何特征;(3) 对简化的几何形状进行分割,因为单次地震并不总能造成断层系统全长的断裂。然而,在缓慢变形的地区,由于缺乏清晰的活动断层痕迹,即使存在大地震的地质记录,断层模型的构建也具有挑战性。事实上,地表破坏性地震可能不属于历史时期,因为其重现时间长达数千年或更久。尽管如此,对于缓慢变形地区的人口稠密区和工业区,如韩国,还是需要进行地震灾害分析。根据之前建立的断层模型分段几何形状的判定标准,我们在此提出一种方法,用于确定缓慢变形地区的走向滑动断层系统的分段几何形状。在用于确定区段边界的标准方面,我们不仅研究了断层几何形状的沿断层变化,还研究了断层周围岩性和与断层相关的地貌特征的沿断层变化。梁山断层是朝鲜半岛最活跃的发震走向滑动断层之一,我们通过对梁山断层的案例研究检验了评估断层分段几何形状的方法。结果表明,梁山断层在陆地上的长度为 200 千米,由 12 到 15 个不同的断层段组成。我们讨论了断层分段几何模型如何能够改善历史上未发生过地表断层地震地区的地震危险分析。
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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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