The CE 1303 Hongdong Earthquake and the Huoshan Piedmont Fault, Shanxi Graben: Implications for Magnitude Limits
The CE 1303 Hongdong Earthquake and the Huoshan Piedmont Fault, Shanxi Graben: Implications for Magnitude Limits
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CE 1303洪洞地震和山西地堑霍山山前断裂：对震级限制的影响
DOI：
10.1002/2017jb014928
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Lisi Bi
中科院分区：
文献类型：
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作者：
Yueren Xu;Honglin He;Qidong Deng;Mark B. Allen;Haoyue Sun;Lisi Bi
洪洞地震于公元 1303 年 9 月 25 日发生在中国北部的山西地堑系统，此前曾被认为是中国有记录的第一起 M 8 级地震（造成约 27 万人死亡）；如果这一震级估计得到证实，这将是一次异常大的大陆正断层地震。洪洞地震对于了解华北地区的区域构造和地震风险也具有重要意义。我们提供了霍山山前断层 (HPF) 五个海沟中迄今为止记录的 31 个 AMS-14C 年龄的地震，该断层被解释为洪洞事件的致病断层。我们使用高分辨率图像来解释断层痕迹，并详细绘制洪洞地震表面破裂图。确定了四个事件，其时间限制分别为距今 1060-590 年（解释为公元 1303 年事件）、距今 3,310-3,210 年、< 5,460-5,380 年 BP 和 < 26,380 年 BP。后三个事件的复发间隔约为 2,000-3,000 年。我们确认洪洞地震的破裂长度约为98 km，典型震程为3.5 m，最大震程≤5.0 m。简单的标度关系和矩震级标度关系可产生 Mw 7.2-7.6 范围内震级的最佳估计。推导出的全新世晚期延伸速率为~0.6-0.9 mm yr-1，而更新世晚期速率为~0.14 mm yr-1。之前对 M 8 的确定是基于震动强度和报告的高死亡人数，并且可能是高估的。正断层地震的震级上限比逆冲断层小，因为它们相对陡峭的倾角会在发震层底部产生交点，其下倾宽度比缓倾逆冲断层更小。洪洞事件也不例外。历史释放的地震矩可能比之前计算的更接近累积矩。
The Hongdong earthquake occurred in the Shanxi Graben System, North China, on 25 September AD 1303, and has previously been suggested to be the first M 8 event recorded in China (with ~ 270,000 deaths); if this magnitude estimate is confirmed it would be an unusually large continental normal fault earthquake. The Hongdong earthquake is also important for understanding regional tectonics and seismic risk in North China. We present 31 AMS-14C ages to date earthquakes recorded in five trenches, in the Huoshan Piedmont Fault (HPF), which is interpreted to be the causative fault for the Hongdong event. We use high-resolution imagery to interpret fault traces, and map the Hongdong earthquake surface rupture in detail. Four events are identified with timings constrained at 1060-590 yr BP (interpreted as the AD 1303 event), ~ 3,310-3,210 yr BP, < 5,460-5,380 yr BP, and < 26,380 yr BP, respectively. The later three events have a recurrence interval of ~ 2,000-3,000 yr. We confirm that the Hongdong earthquake had a rupture length of ~98 km, with representative throw of 3.5 m and a maximum throw of ≤5.0 m. Simple scaling relationships and a moment magnitude scale relationship yield best estimates for magnitude in the range Mw 7.2-7.6. The derived late Holocene extension rate is ~0.6-0.9 mm yr-1, while the late Pleistocene rate was ~0.14 mm yr-1. Previous determination of M 8 was based on shaking intensity and the high reported death toll, and is likely to be an over-estimate. Normal fault earthquakes have smaller upper limits to their magnitudes than thrusts, because their relatively steep dips produce intersections at the base of the seismogenic layer at smaller down-dip widths than gently-dipping thrust faults. The Hongdong event was not an exception to this pattern. The historic released seismic moment may be closer to the accumulated moment than previously calculated.