Abstract Major active strike-slip fault zones in graben systems play an important role in releasing the strain energy. In this study, the active tectonics, paleoseismicity and seismic hazards of the Xizhoushan Fault Zone (XFZ) in the Shanxi graben system, North China Block (NCB), are examined through high-resolution satellite image interpretations, field investigations, outcrop and trench excavations, and dating of geochronology samples. Modern alluvial terraces of gullies and loess accumulations are systematically deflected and/or offset with co-seismic collapse, landslides and scarps, indicating that the XFZ has been active in the late Quaternary and is characterized by normal dextral strike-slip movements. The late Holocene slip rate of the XFZ is estimated to be ~2.0 ± 0.2 mm/yr in the horizontal and 0.5 ± 0.10 mm/yr in the vertical. Field observations reveal that at least three morphogenic earthquakes occurred on the XFZ in the Holocene, hinting at an average recurrence interval of ~3000 yrs. The latest event occurred at ~1.50 ± 0.6 ka BP and very likely corresponds to the 1038 CE Dingxiang M 7¼ event. The penultimate event occurred at ~4.10 ± 1.60 ka BP, and the antepenultimate event is inferred to have occurred between ~13.17 ± 1.43 ka BP and ~8.29 ± 0.90 ka BP. Our studies suggest that the strain energy accumulating along the XFZ is released by repeated strike-slip displacements of the modern stream channels, alluvial terraces and loess accumulations, while the earthquake potential (M ≥ 7) is low in the short term. The research also hints that the present dextral slip along NNE-trending faults has replaced the once predominately extensional deformation in the NCB.

中文翻译：

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华北地块山西地堑系西洲山山前断裂带活动构造、古地震与地震灾害

摘要 地堑系统中主要的活动走滑断裂带对释放应变能具有重要作用。在这项研究中，通过高分辨率卫星图像解释、野外调查、露头和沟渠开挖，研究了山西地堑系统华北地块 (NCB) 西洲山断裂带 (XFZ) 的活动构造、古地震和地震灾害。 ，以及地质年代学样本的测年。沟壑和黄土堆积的现代冲积阶地系统地偏转和/或被同震崩塌、滑坡和陡坡抵消，表明XFZ在第四纪晚期一直活跃，并以正常的右旋走滑运动为特征。XFZ 晚全新世的滑动速率估计为水平方向~2.0 ± 0.2 mm/yr 和垂直方向 0.5 ± 0.10 mm/yr。现场观测表明，在全新世的 XFZ 上至少发生了 3 次形态发生地震，暗示平均复发间隔约为 3000 年。最新事件发生在~1.50 ± 0.6 ka BP 并且很可能对应于 1038 CE 丁香 M 7¼ 事件。倒数第二个事件发生在 ~4.10 ± 1.60 ka BP，倒数第二个事件发生在 ~13.17 ± 1.43 ka BP 和 ~8.29 ± 0.90 ka BP 之间。我们的研究表明，沿XFZ积累的应变能是由现代河道、冲积阶地和黄土堆积物的反复走滑位移释放的，而短期内地震潜势（M≥7）较低。研究还表明，目前沿 NNE 向断层的右旋滑移已经取代了 NCB 中一度以伸展变形为主的变形。