地震过程中新生断层破裂的扩展有限单元法(XFEM)模拟  

Simulation of fresh fault cracks in an earthquake based on the extended finite element method(XFEM)

作　　者：崔泽飞 朱守彪 CUI ZeFei;ZHU ShouBiao(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;National Institute of Natural Hazards,Ministry of Emergency Management of China,Beijing 100085,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]应急管理部国家自然灾害防治研究院,北京100085

出　　处：《地球物理学报》2025年第2期564-577,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42374074,41874060);国家自然灾害防治研究院院长基金项目(ZDJ2020-15)联合资助

摘　　要：地震破裂过程的数值模拟通常是假定破裂发生在先存断层上.但是,实际地震过程中,除了沿着先存断层产生自发破裂外,很有可能会产生新的破裂.为此,本文将传统有限元与扩展有限元方法(Extended Finite Element Method,XFEM)相结合,首先利用传统有限元方法模拟先存断层上的自发破裂过程,随后采用扩展有限元方法模拟不同介质(内摩擦角分别为0°、22.5°和45°)中,由于先存断层破裂造成的断层尖端应力集中导致的新生破裂过程.当内摩擦角为0°时,2条新生破裂与先存断层走向之间的夹角分别为0°和90°;当内摩擦角为22.5°时,该夹角变为11.25°和78.75°;当内摩擦角为45°时,该夹角变为22.5°和67.5°.在这三种情形下,新生的2条破裂,相互垂直,但破裂特征(破裂长度及破裂速度)不同,与先存断层之间的夹角越小的新生破裂,其扩展距离越远,扩展速度也更快(甚至为超剪切破裂).此外,在模拟结果中,岩石强度越低,断层扩展的长度越长,扩展速度也越快.本研究对于地震破裂全过程的数值模拟、深刻认识地震震源过程、断层生长以及地震灾害评估等有着重要的科学意义.Conventional simulation methodologies for spontaneous rupture process assume that the rupture occurs exclusively along pre-existing fault.However,in the nature earthquake,in addition to the rupture along the pre-existing fault,it is highly probable for a new rupture to occur.Therefore,we have integrated the traditional finite element method with the extended finite element method(XFEM)in this study.The traditional finite element method is utilized to simulate the spontaneous rupture process along the pre-existing fault,then the extended finite element method is employed to simulate the new rupture process induced by the stress concentration at the fault tip resulting from the rupture of the pre-existing fault in different media with internal friction angles of 0°,22.5°,and 45°,respectively.When the internal friction angle is 0°,the angles between the new rupture and pre-existing faults are 0°and 90°,respectively.When the internal friction angle is 22.5°,these angles become 11.25°and 78.75°.When the internal friction angle is 45°,these angles become 22.5°and 67.5°.It should be noted that the two new faults are perpendicular to each other in these three scenarios,and the rupture characteristics(rupture length and rupture velocity)are different.The new rupture with a smaller angle exhibits a greater extension distance and a faster propagation speed(even achieving super shear rupture).Additionally,lower rock strength corresponds to greater fault extension and faster crack speed.This research holds significant scientific importance as it contributes to the numerical simulation of earthquake rupture processes,deepens our understanding of the earthquake process,fault growth and earthquake disaster assessment.

关 键 词：有限元单元法 扩展有限元法(XFEM) 断层自发破裂 新生断层破裂 内摩擦角 

分 类 号：P315[天文地球—地震学]