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This article made a systematic statistical analysis on the duration,spatial distribution,form,range,type and reliability of precursory anomalies based on the observations of precursors of 24 moderate-strong earthquakes occurring along the Tancheng-Lujiang fault zone and its bilateral areas in Shandong,Liaoning,Hebei,Jiangsu and Jiangxi Provinces in the period from 1966 to 2005. Results show that:( 1) For M7. 0 and M6. 0earthquakes,med-term abnormities are the greatest in number,short-term abnormities come second,and imminent anomalies are the least. For M5. 0 earthquakes,short-term abnormities are often the most in number,imminent anomalies come second,and the med-term ones are the least.( 2) Precursory anomalies are periodical,part of the med and short-term anomalies are shown as short-term and imminent anomalies during their development.( 3) The development of precursor shows quasi-synchronism; the closer to earthquake occurrence time,the more turning changes of anomalies will appear.( 4)Anomalies mainly occur within an epicenter distance of 100 km, showing a relative concentrated distribution in space,and the shorter the distance to epicenter,the higher the anomaly station / item rate.( 5) The spatial distribution of anomalies is relatively correlated to the strike of structures,having a good consistency with the structure.( 6)There is no significant correlation between duration of abnormities and the epicenter distance.( 7) The higher the magnitude of the earthquake,the greater the amplitude of the abnormities measured with the same observation approach.( 8) In terms of the itemsof the observations,fluid abnormities are the greatest in number,followed by deformation and electromagnetism observations.( 9) For all observation items,med and short-term abnormities make up the majority and short-term and imminent anomalies the minority.( 10) In fluid,deformation and electromagnetism observations,fairly reliable anomalies are about double the number of reliable anomalies.
This article made a systematic statistical analysis on the duration, spatial distribution, form, range, type and reliability of precursory anomalies based on the observations of precursors of 24 moderate-strong earthquakes occurring along the Tancheng-Lujiang fault zone and its bilateral areas in Shandong , Liaoning, Hebei, Jiangsu and Jiangxi Provinces in the period from 1966 to 2005. Results show that :( 1) For M7. 0 and M6. 0earthquakes, med-term abnormities are the greatest in number, short-term abnormities come second, for M5. 0 earthquakes, short-term abnormities are often the most in number, imminent anomalies come second, and the med-term ones are the least. (2) Precursory anomalies are periodical, part of the med and short-term anomalies are shown as short-term and imminent anomalies during their development. (3) The development of precursor shows quasi-synchronism; the closer to earthquake occurrence time, the more turning changes of anomalies will appear (4) Anomalies mainly occur within an epicenter distance of 100 km, showing a relative concentrated distribution in space, and the shorter the distance to epicenter, the higher anomaly station / item rate. (5) The spatial distribution of anomalies is relatively correlated to the strike of structures, having a good consistency with the structure. (6) There is no significant correlation between duration of abnormities and the epicenter distance. (7) The higher the magnitude of the earthquake, the greater the amplitude of the abnormities (8) In terms of the items of the observations, fluid abnormities are the greatest in number, followed by deformation and electromagnetism observations. (9) For all observation items, med and short-term abnormities make up the majority and short-term and imminent anomalies the minority. (10) In fluid, deformation and electromagnetism observations, fairly reliable anomalies are about double the number of reliable anomalies.