断层岩磁学研究及其意义

Magnetic study of fault rocks and its implications

断层岩的物理、化学及结构特征是直接了解断层活动特性、形变环境、破裂摩擦机制等地震学特性,评价地震危险性与认识地震物理化学行为的最基本证据.本文对断层岩磁学研究这一岩石磁学与地震学交叉新领域的研究现状进行了总结论述.已有研究表明,断层岩的磁学研究能够为断层区域应力环境及应变历史、断层带温度状态、热事件及热历史、断层活动历史与古地震及同震电流现象等方面的研究提供重要的磁学依据.然而,由于断层岩磁性特征受其磁性矿物的种类、含量和粒度、断层物理化学环境及后续地质作用的影响,因此,作为岩石磁学应用研究的新领域,断层岩的磁学研究亟需深入和加强.本文建议,应积极开展脆性破裂岩石的磁学研究,加强断层泥的高速摩擦实验、断层岩的机械摩擦和摩擦熔融实验,强调结合岩石学、矿物学、地球化学及磁性矿物学等多学科手段进行断层岩的综合研究,以深化对断层岩磁性变异机制的认识与理解,更好地为地震物理化学行为研究提供岩石磁学证据.

Physical, chemical and textural properties of fault rocks are related directly to fault behaviors, deformation environments, rupture mechanisms and friction of faults. They are the basic evidences for assessment of seismic risk and understanding the physical and chemical behaviors of earthquakes. In the present paper, the recent research progress in magnetic study of fault rocks, which could be a new branch of rock magnetism applied to seismology, has been reviewed. The available studies have proved that magnetic study of fault rocks can provide important magnetic evidence for investigation of stress environment and strain history, thermal state, history and events in fault zones, fault activity history and paleoseismicity, coseismic electrical currents, and so on. However, magnetism of fault rocks is complicated by magnetic mineralogy, physicochemical environment and subsequent geological processes in fault zones. As a new research field of rock magnetism, consequently, it needs urgently to develop magnetic study on fracture of brittle rocks, to strengthen the high-velocity frictional tests of gouge, mechanical friction and frictional melting experiments of fault rocks, and to conduct integrated studies combined with petrology, mineralogy, geochemistry and magnetic mineralogy, in order to improve and deepen the understanding of mechanism of magnetic responses of rock in fault zones, which could help understand the physical and chemical behavior of earthquakes.