【作者】 吴彦；

【导师】 陈晓非；

【作者基本信息】 中国科学技术大学 ， 固体地球物理， 2014， 博士

【摘要】 本文详细介绍了基于岩石摩擦实验提出的速率和状态摩擦准则,并研究了其在数值模拟震源参数变化、地震复杂性以及破裂动力学中的作用。断层滑动和地震破裂的物理机制主要受接触面上摩擦准则的控制,对岩石摩擦的认识是理解断层和地震行为的关键。因此本文首先详细回顾了速率和状态摩擦准则的发现过程及其基本特征,系统分析了该准则在简单的单自由度弹簧滑块模型下的稳定性问题,也简要介绍了最近十年来岩石高速摩擦下的最新实验室发现,以及相关的强弱化理论。总之对岩石摩擦的全面且系统的认识有助于理解断层和地震现象的本质。观察震源参数随地震矩的变化一直是地震学家了解地震自相似性的手段之一。本文利用简单的单自由度弹簧滑块模型,数值模拟了速率和状态准则控制下的系统所表示的震源参数的变化。在该模型下,地震的大小主要由断层的尺度W(与模型中弹性刚度k成反比)控制。震源参数的变化受断层相对尺度(断层尺度W与成核尺度hc。的比值)的影响,对较小的地震,因为非震滑移和断裂能的比重比较大,震源参数有尺度效应；对较大的地震,非震滑移和断裂能可忽略,震源参数可视为自相似的。但是当考虑了热增压效应后,震源参数呈现非常明显的变化,视应力和应力降都随着地震矩的增加而明显增加。本文发展了基于时间域牵引力边界积分的可同时模拟长时间尺度下断层滑动行为和极短时间尺度下同震过程的数值方法,并将其与准动态的数值模拟方法做了比较。尽管在同震过程准动态方法显然不能正确地模拟地震波效应,但是在均匀的或轻微非均匀的断层模型下,两者能给出大致相似的滑动模式(地震序列)和破裂风格(裂纹型或脉冲型)。本文同时利用准动态和新发展的动力学数值方法,研究了断层的相对尺度W/hc。对地震破裂特征和滑动复杂性的影响。发现当断层的相对尺度较小时,断层行为表现简单的周期性的裂纹型地震,当断层的相对尺度较大时,断层除了继续产生特征地震以外,会自发地产生更多自发停止的自愈合地震,这可能预示着均匀断层在相对尺度充分大的情况下,能自发地产生丰富的地震活动性。总体上本文的研究显示速率和状态摩擦准则存在明显的尺度效应。断层相对尺度W/hc影响了断层和地震各方面的特征,地震的微观破裂特征和其宏观的活动复杂性在速率和状态摩擦准则下得到了统一的解释。更多还原

【Abstract】 The laboratory-derived rate-and state-dependent friction law is introduced. We study how the friction law affects and controls the scaling of source parameters, seis-mic slip complexity, as well as rupture dynamics for a fault model obeying the law. The friction on the fault surface has strong influences on the natural fault behavior and earthquakes. Our understanding in the fault slip and earthquakes depends on how much we known about friction. Therefore, we first detailed review how the rate and state fric-tion law is proposed and developed, and then, give the stability analysis under a simple single-degree-of-freedom spring-slider model, and also summarize the latest friction facts from high-speed rock friction experiments over the past decade, as well as related thermal weakening theories. A comprehensive and systematic knowledge of the rock friction serve to understanding of the nature of faults and earthquakes.The field observation of source parameters varying with the seismic moment is one way by which seismologists explore the self-similarity of earthquakes. In this study, a single-degree-of-freedom spring-slider model is used to numerical simulate the implied scaling relation of source parameters under the rate-and state-dependent friction law. In this case, earthquake size is controlled by the fault size W (being inversely propor-tional to the stiffness k) and source parameters are affected by the ratio of W and the nucleation size hc. The simulation result shows source parameters are scale-dependent for small events, but are almost self-similar for large events. The transition is attribut-ed to the relatively large proportion of both aseismic slip and fracture energy in small events. However, the model shows evident increase in stress drop and apparent stress if a thermal pressurization is included.A numerical method that could simulate both the fault slip behavior in very long time-scale and co-seismic process in extremely short time-scale, based on the traction boundary integral equation method in time domain, is developed and compared with widely used quasi-dynamic method. The two methods produce generally similar slip patterns and rupture styles in an uniform or slightly nonuniform fault model, although the latter cannot represent the seismic wave effects correctly in the co-seismic process. The effect of the relative fault size W/hc on the rupture style and the slip complexity is studied by both the quasi-dynamic and new developed dynamic methods. It is observed that the fault with a small W/hc produces regular, periodic crack-like characteristic event and the fault with a large W/hc produces the similar event, as well as more self-stopping and pulse-like events. It implies an uniform fault would spontaneously evolve into complex slip patterns with increasing W/hc.This study indicates the rate-and state-friction law is scale-dependent. The rel-ative fault size W/hc affects all aspects of faults and earthquakes. The micro-scale rupture characteristics and the macroscopic seismic complexity hence have an unified interpretation under the friction law.更多还原