断裂带中-深部的流体传输性质及其地震动力学意义:以红河断裂带为例

断裂带的流体传输性质(渗透率、孔隙度与比储流率)是理解流体在地震过程中作用的主要参数.目前对断裂带流体传输性质的研究大多集中在浅部,对断裂带中-深部(强震孕育成核区)的研究较少,限制了人们对流体在强震孕育成核过程中作用的理解.与之相关并亟待解决的科学问题包括:(1)流体的同震热压作用在断裂带中-深部能否发生;(2)含水情况下假玄武玻璃的形成条件;(3)脆塑性转换带附近地震成核与伴随的扩容演化机制.本项目以解决上述科学问题为研究目标,对红河断裂带开展跨断层的流体传输性质实验,建立深部流体活动模型.开展模拟深部断层同震滑动的高速摩擦实验,结合实验和数值模拟结果探讨断裂带深部同震热压作用与摩擦熔融的形成条件,阐明两者之间的关系.开展模拟脆塑性转换带深度附近地震成核的摩擦滑动及同步渗透性测量实验,根据实验结果探索地震成核过程及伴随的扩容与孔隙演化规律,分析扩容对成核过程及破裂传播与扩展的影响.

Fluid transport properties (permeability, porosity, and specific storage) are important parameters for understanding the role of fluids during seismic activities. Currently, studies on the fluid transport properties are mostly focused on the shallow portions of fault zones, while the middle-deep portions (seismogenic zone), where cataclasites and mylonites develop have been rarely concerned, and thus limit our understanding of the role of fluids in seismogenic processes. The related key scientific questions needed to be addressed are: (1) whether coseismic thermal pressurization can occur at middle-deep depths conditions; (2) how does pseudotachylite form with the presence of water; (3) the mechanisms of earthquake rupture nucleation and accompanying dilatation and pore evolution at the brittle-ductile transition zone. To address the above-mentioned questions, this project will perform detailed fluid transport property measurement experiments and establish the fluid flow model of the Red River fault zone at depths. High velocity friction experiments will be conducted to reproduce rapid coseismic fault motion. Combining experimental and numerical results, we will investigate the conditions for coseismic thermal pressurization and friction melting and their relationships. Friction experiments coupling permeability measurement at conditions relevant to brittle-ductile transition will be performed to investigate the mechanisms of earthquake nucleation and accompanied dilatation and pore cavitation and discuss the effect of dilatation on rupture propagation.