断层接触非均匀性对米尺度断层黏滑失稳成核过程的控制  

The control of fault contact heterogeneity on the nucleation process of stick slip instability of meter scale faults

作　　者：任雅琼[1,2] 谢凡 卓燕群[3] REN YaQiong;XIE Fan;ZHUO YanQun(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Earthquake Source Physics,China Earthquake Administration,Beijing 100081,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局震源物理重点实验室,北京100081 [3]中国地震局地质研究所,地震动力学国家重点实验室,北京100029

出　　处：《地球物理学报》2024年第6期2336-2349,共14页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2018YFC1503301);中国地震局地球物理研究所基本科研业务费专项(DQJB19B46);国家自然科学基金(41802231);国家自然科学基金(U2239205)联合资助。

摘　　要：非均匀性是野外断层的重要特征,我们利用预制的具备接触非均匀性的米尺度岩石断层开展黏滑实验,模拟野外地震失稳过程.通过观测预制岩石断层发生的多个黏滑事件的应变时空演化,并对比断层接触非均匀性测定结果发现:(1)断层的接触弱段是成核最先启动,即最早发生预滑的区域,随失稳临近,预滑区域扩展且滑动速率增加,与厘米尺度均匀断层相比,准静态过程的预滑扩展不明显,向准动态过程转变突然且迅速;(2)断层的接触强段在成核期间一直处于闭锁状态,应力升高,且随失稳临近增幅加强,强段的屈服是断层从缓慢破裂到快速破裂的转折点,接触强段的持续闭锁在以往的厘米尺度均匀断层黏滑实验中较为少见;(3)加载速率以及加载历史是影响米尺度断层成核持续时间的重要因素,随加载速率变慢,成核持续时间变长,随加载历史变长,断层趋于均匀化,成核持续时间变短.上述研究结果明确提供断层接触非均匀性控制成核过程的直接证据.这不仅有助于将实验结果向可操作的地震预测实践转化,也有助于促进(大陆浅源)地震前兆机理的探索及理解.Fault heterogeneity is an important characteristic of natural faults.In order to simulate seismic instability processes in the field,we conducted stick-slip experiments using heterogeneously contacted precut meter-scale rock faults.We observed the spatial and temporal evolution of strain in multiple stick-slip events and compared it with measurements of fault contact heterogeneity.We demonstrate that the weak contact segment of the fault exhibits the earliest pre-slip,and thus serves as the initiation region for nucleation.As the instability approaches,the pre-slip area expands and the slip rate increases.In comparison to centimeter-scale homogeneous faults,the pre-slip extension during the quasi-static process is minimal,while the transition to the quasi-dynamic process is sudden and rapid.We also find that the strong contact segment of the fault remains locked throughout the nucleation stage,with stress continuously building up.As the impending instability approaches,strain concentration gradually increases.The yielding of the strong section marks the moment when the fault rupture rate shifts from slow to fast.Sustained locking within strong contact segments is relatively uncommon in stick-slip experiments of centimeter-scale homogeneous fault.In addition,the loading rate as well as the loading history are important factors affecting the duration of nucleation on meter-scale faults.Slower loading rates result in longer nucleation durations,while extended loading histories tend to homogenize faults and subsequently reduce nucleation durations.The aforementioned studies yield explicit evidence that the spatial distribution of fault contact heterogeneity has a direct influence on the spatial and temporal progression of the nucleation process.These findings not only contribute to applying experimental results to operational earthquake forecasting practices,but also facilitate the exploration and comprehension of earthquake precursor mechanisms,particularly those related to continental shallow sources.

关 键 词：摩擦 黏滑 地震成核 断层接触非均匀性 预滑 

分 类 号：P541[天文地球—构造地质学]