DISCUSSION ON THE DISTRIBUTION CHARACTERISTICS OF SUBSURFACE FLUID ANOMALIES BEFORE THE HEZE 1983 M5.9 EARTHQUAKE AND THE RELATIVE ISSUES CONCERNED

This paper has completely and systematically analyzed the spacio-temporal distribution of subsurface fluid anomalies before the Heze M5.9 earthquake and the characteristics of its field precursor and source precursor. The result shows that the spacio-temporal distribution of the anomalies is more closely related to active tectonics, the ends and intersections of faults are sensitive areas of anomalies.The number of anomalous items in per unit area is higher in the epicenter and its near area than in the outlying area. About one month before the earthquake, the monthly frequence of anomalous items increased with large amplitude, the time evolution of single anomaly in three types, that is continous type,complete type and sudden jump type. Source precursor anomalies showed characteristics of a complete set of long term, short term and imminent anomalies, of synchronous anomalous variation of hydrochemical multi-components, macroscopic anomalies at many points, long time and large amplitude. The fiekd precursors are mainly short term and imminent anomalies, showing single items. The anomaly at a single point showed characteristics of short time and small amplitude. This paper also has discussed the relation between field precursor, source precursor and stress field, the relation between anomalies distribution and tectonics, the relation between spacio-temporal distribution of anomalies and earthquake occurrence place, and the relation between spacio-temporal distribution of anomalies and earthquake occurrence time.