5级以上地震前中小地震的统计研究

Statistical study on the earthquakes of M_L≥5.0 in China

通过对中国1980～2004年6月期间5级以上地震的研究，统计中国西部、华南、华北5级以上地震震前是否有系列小地震发生。结果表明：5级以上地震在震前不同时期。距震中近距离范围内有系列的小地震发生；在6级地震前50km范围内有系列3～4级地震发生，概率为44％左右；西部7级地震前会有系列的4～6级地震发生，发生4级地震的概率为44％左右，发生5～6级地震的概率为11％左右。

By means of the research on the events of M≥5.0 in China that occurred during the period from January 1980 to June 2004, the occurring of minor earthquakes before the events of M≥5.0 in Western, Northern and Southern China region was statistically studied. The result indicates that before a mainshock of M ≥5.0, a series of minor events in the different period and distances away from epicenters for the M≥ 5. 0 events would occurred. The probability of earthquakes of M 6.0 with a series of pre-seismic events of ME 3. 0 to 4. 0 occurred within 50 km away from its epicenter is 44%. However, before a mainshock of M 7.0 in western China, a series of events of ME 4. 0, M 5. 0 and 6. 0 occurred. The probability for the pre-seismic events of ME 4.0 is 44% and 11% for those of M 5.0 and 6.0.