活动断裂带岩石的变形机制和摩擦性质——以圣·安德列斯断层为例  

Deformation mechanisms and frictional properties of rocks in active faults:Insights from the San Andreas Fault

作　　者：金田龙 王勤[1] Jin Tianlong;Wang Qin(School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,Jiangsu,China)

机构地区：[1]南京大学地球科学与工程学院,江苏南京210023

出　　处：《地质学刊》2021年第4期375-383,共9页Journal of Geology

基　　金：国家重点研发计划深地资源勘查开采专项课题“中国大陆壳幔结构与燕山期成矿的深部动力学”(2017YFC0601406)。

摘　　要：岩石的变形机制和力学性质对认识活动断裂带的孕震机制和发震过程都具有重要意义。圣·安德列斯(San Andreas)转换断层是太平洋板块与北美板块的构造边界,也是重要的地震活动带,总结了美国南加州地震中心对圣·安德列斯断层钻孔断层岩的研究进展。对断层泥的高速摩擦实验发现:动力弱化现象只在高速滑移时才发生,伴随着摩擦生热,岩石的摩擦系数显著降低。断层泥中富镁黏土矿物的富集可以显著降低断层的摩擦系数,促进蠕滑,黏土矿物的不均一分布可导致断裂带变形行为和地震分布的突变。与断层泥和碎裂岩不同,粉碎岩形成于快速传播地震的断裂端部,具高孔隙率和高渗透率,流体活动性强。此外,断层岩的有机质成熟度可用来追溯古地震造成的热异常。在川滇中国地震科学实验场开展科学钻探项目,研究断层岩样品的显微结构、物理性质和变形历史,以期为理解大陆汇聚与转换挤压过程中复杂的地震活动提供重要信息。Deformation mechanisms and mechanical properties of rocks are critical for seismogenic mechanisms and process in active fault belts.As the boundary between the Pacific Plate and the North American Plate,the San Andreas transform fault is an important seismic zone.This paper reviewed experimental studies of core samples from the San Andreas Fault observatory at Depth(SAFOD),which were mainly carried out by the Southern California Earthquake Center in the U.S.A.The high-speed friction experiments found that associated with frictional heating,dynamic weakening of fault gouges only occurs at high-speed slip rate.This can significantly decrease the fraction coefficients of fault rocks.Accumulation of magnesium-rich clay minerals in fault gouge can reduce the fraction coefficients of faults and trigger creep.Consequently,heterogenous distribution of clay minerals in fault belts will result in sudden change in deformation behavior and earthquake activity.In contrast to fault gouge and cataclastic rocks,pulverized rocks were formed at tip regions of earthquake ruptures with fast propagation rates.Pulverized rocks show high porosity and high permeability,allowing high fluid activity.In addition,organic thermal maturity of fault rocks provides an effective way to trace frictional heating signature of plaeo-earthquakes.Hence,scientific drilling projects in the China Seismic Experimental Site in Sichuan and Yunnan provinces will help to study microstructure,physical properties and deformation history of fault rocks,which will improve the understanding of complex earthquake activity during continental convergence and transpression.

关 键 词：地震动力学 断层泥 摩擦系数 粉碎 热成熟度 科学钻探 圣·安德列斯断层 

分 类 号：P545[天文地球—构造地质学]