Constraining Paleoseismicity of the Wulashan Piedmont Fault on the Northern Margin of the Ordos Block From Fault Scarp Morphology
Constraining Paleoseismicity of the Wulashan Piedmont Fault on the Northern Margin of the Ordos Block From Fault Scarp Morphology
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DOI：
10.3389/feart.2022.911173
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
H. Bi;Lin Shi;Dongli Zhang;Hui Peng;Jingjun Yang;Zicheng You;Xinzhe Sun
中科院分区：
文献类型：
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作者：
H. Bi;Lin Shi;Dongli Zhang;Hui Peng;Jingjun Yang;Zicheng You;Xinzhe Sun
断层陡坡保存了断层上过去地震的重要信息，因此可以用来研究断层滑动历史和破裂模式。基于高分辨率激光雷达地形，利用断裂带形态对鄂尔多斯地块北缘乌拉山山前断裂带古地震活动性进行了约束。通过对断层沿线不同地貌面上提取的大量陡坡剖面高度进行测量，构建了断层的垂直位移分布。通过对密集收集的垂直位移数据集的统计分析，确定了7个古地震事件，这些地震事件具有平均滑动量为~ 1.0 m的特征滑动模式。我们进一步检测断裂带形态中的坡折，以量化断裂带上发生的古地震次数，并区分出至少5次单独的地表破碎事件。断裂带形态识别的古地震次数和滑动量与前人的古地震沟陷记录吻合较好。根据弯矩震级与破裂参数的经验标度关系，确定了该断层发生的古地震的弯矩震级为6.7 ~ 7.5。根据前人研究得到的断层滑动率，我们估计古地震事件的平均重现间隔为1.3 ~ 1.8 kyr，这与最近一次地震发生的时间非常接近，表明乌拉山山前断裂具有较高的地震危险性。
Fault scarps preserve important information about past earthquakes on a fault, and thus can be applied to investigate the fault slip histories and rupture patterns. In this study, the morphology of fault scarps was used to constrain the paleoseismicity of the Wulashan Piedmont Fault located on the northern margin of the Ordos Block based on high-resolution LiDAR topography. We constructed the vertical displacement distribution of the fault through measuring the heights of a large number of scarp profiles extracted on different geomorphic surfaces along the fault. Through statistical analysis of the dense collection of vertical displacement dataset, a total of seven paleoseismic events were identified which followed a characteristic slip pattern with an average slip of ∼1.0 m. We further detected slope breaks in the fault scarp morphology to quantify the number of paleoearthquakes that occurred on the scarps, and discriminated at least five individual surface-breaking events. Both the number and slip of paleoearthquakes recognized from the morphology of fault scarps were in good agreement with previous paleoseismic trenching records. Based on the empirical scaling relationship between moment magnitude and rupture parameters, a moment magnitude of M w 6.7–7.5 was determined for the paleoearthquakes occurred on the fault. With the fault slip rate derived by previous studies, we estimated an average recurrence interval of 1.3–1.8 kyr for the paleoseismic events, which is very close to the elapsed time since the most recent earthquake, indicating a high potential seismic hazard on the Wulashan Piedmont Fault.