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《Chinese Journal of Geophysics》 1994-02
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APPLICATION OF THE MT REPEATED MEASUREMENTS TO THE MEDIUM AND SHORT TERM PREDICTION OF EARTHQUAKE──MONITORING AND STUDYING A PROFILE IN THE MIDDLE SEGMENTOF QILIAN MOUNTAIN BY MT

ZHANG YUN-LIN; LIU XIAO-LING; AN HAL-JING; SI YU-LIN; JIANG MEI; ZHANG WU-SHI (Seismological Institute of Lanzhou, State Seismological Bureau, Lanzhou 730000)(Seismological Bureau of Hainan Province, SSB, Haikou 570004.)  
This paper deals with the newest data to do some researches on the earthquake prediction by MT repeated measurements. The data are from the first MT monitoring profile about 400km long in north margin of Qinghai-Tibet Plateau. Five earthquakes of M 5 to M 7 occurred during monitoring along the profile. After studying several MT parameters of the time and space domains on the basis of the error analysis, we found the perfected parameter of the MT monitoring and the perfected frequency range of the MT monitoring. During the activity of great earthquakes accompanied by strong earthquakes and at the depth equal to that of most continental earthquakes (between 10km and 20km from surface), the apparent resistivity of the measurement coordinate axis, apparent resistivity of the main axis, apparent resistivity of the real part and apparent resistivity of the imaginary part all show that the electroconductibility of the media changes in form of drop-rise-recovery,and the skewness and azimuth of the main axis show that the cross heterogeneity of electricity is abated apparently. At the same time, the synchronous and same-phase variations of the MT parameters in wide range might correspond to the regional precursors of great tectonic earthquakes. The lead and lag variations of the MT parameters between local regions, the relative variation amplitude declines as the distance from the focus increases, might correspond to the regional precursors of the strong earthquake which is caused by the movement of the structures. This forms a chain-like relationship in which large background of seismicity is superposed on it small background. The cause about the case has been studied in detail.Monitoring of perfected MT profile can provide rich and reliable criteria for development processes of continental earthquakes and mid- and short-term earthquake prediction.
【Fund】: 地震科学联合基金
【CateGory Index】: P315.7
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