1927年古浪8级地震的破裂习性及破裂机制的数值模拟

Rupture Property in the Gulang M_S 8.0 Earthquake, 1927 and Numerical Simulation of Rupture Mechanism

192 7年古浪 8级地震是继 192 0年海原 8 5级地震之后发生在海原 -祁连山断裂带上的另一次特大地震。对这次地震的破裂习性 ,前人的研究结果存在较大分歧。本文在多探槽揭露和地面追踪调查基础上 ,结合相关的历史资料分析后 ,认为本次地震是由构成古浪推覆体的天桥沟 -黄羊川断裂、皇城双塔断裂冬青顶断裂段以及武威 -天祝隐伏断裂等共同作用的结果。对古浪推覆体平面和剖面变形机制的有限元数值模拟结果显示 ,其应力和应变的集中区主要分布在天桥沟 -黄羊川断裂西段、皇城 -双塔断裂冬青顶一带以及武威 -天祝隐伏断裂和古浪 -双塔断裂所在的古浪峡一带 ,这与地震地表破裂带的展布是一致的 ,同时也进一步说明了192 7年古浪 8级地震是该推覆体整体活动的结果。

The Gulang M S 8.0 earthquake in 1927 is the severe earthquake after the Haiyuan M S 8.5 in 1920 occurred in the Qilian Mt.-Hexi corridor earthquake zone. Different divergences of former study on the rupture property. Based on many trenches and field investigation, and analysis of some history data, it is sure that the earthquake is caused by the Gulang nappe activity including the Tianqiaogou-Huangyangchuan fault, Dongqingding segment of the Huangcheng-Shaungta fault and the Wuwei-Tianzhu buried fault. It is a multi-point break. By finite-element numerical simulation, results of deformation mechanism of Gulang nappe show that the major deformations distribute on the west of the Tianqiaogou-Huangyangchuan fault, Dongqingding segment of the Huangcheng-Shuangta fault and the Gulang gorge including the Wuwei-Tianzhu buried fault and the Gulang-Shuangta fault, which is coincident with that of investigation. At the same time,it holds another powerful evidence that the whole nappe activity causes the earthquake.