EXTENDED PROGRESS IN EXPERIMENTAL STUDY ON MECHANISM OF EARTHQUAKE PRECURSORS
Zhang Liu(Institute of Geology, SSB, Beijing 100029, China )Xu Zhaoyong(Seismological Bureau of Yunnan Province, Kunming 650041, China)Lu Yangquan(Lanzhou Institute of Seismology, SSB, Lanzhou 730000, China)
The advanced experimental study on mechanism of earthquake precursors has been performed from two angles of earthquake "source" and earthquake "field" to investigate the time process and space distribution of some physical responses during fracturing of source body at different mechanical status. The results indicate that low axial stiffness will increase the faulting distance, enhance the stress level of the system after fracturing, shorten the period of repeat instability. Deformation behaviour (strain-stress curves) of rock body at different temperature and confining pressure are divided into five groups, which are different in relationship between the strain response-ratio and instability of deformation system (earthquake) . The AE (acoustic emission) activity is studied with cm-scale rock samples of granodiorite, sandstone and marble at different testing condition: constant strain rate, constant energy rate, different stiffness, etc. It is concluded that complicated loading processes offer complicated patterns of micro-fracturing ( AE) . Q value measured with different methods is compared, and the changes of Q value, velocity and amplitude of waves during deformation are studied with 20-30 cm-scale rock samples. The changes of electric characteristics are studied with m-scale rock samples. Two types of precursory anomalies are distinguished as: trend anomaly and abrupt one. They behave as discrepancies in locations and episodes in time. The fracture conditions and precursors of rock body with hard inclusions are studied. It is confirmed that hard inclusions will lead stress to be concentrated. The inclusions may be broken before the confining rock yielding at a certain condition. The spatial patterns of micro-fracturing development and changes of wave velocity field are given.
【CateGory Index】： P315.7