施甸5级震群前中短—短临的地震活动参数动态演化

DYNAMIC EVOLUTION OF SEISMICITY PARAMETERS ON MID-SHORT AND SHORT -IMMINENT TERMS BEFORE SHIDIAN M_S5 EARTHQUAKE SWARM

通过2001年施甸5级震群前地震学各项参数异常的动态追踪,研究了中强地震孕育、发生的中短-短临的演化过程.结果表明:在云南地区出现b值、小震调制比、波速比等地震活动性参数异常以及中强地震的有规律迁移的中期异常背景上,出现了孕震区的频度、b值、应变加速等群体中短异常,以及云南省内的3、4级地震连续增频、3级日频次异常和显著的3、4级地震平静的短临异常.特别是3、4级地震异常平静,标志了明显的临震信息.并初步探讨了中强地震连续发生中如何识别单个地震的震兆问题.

By tracing down anomalies of seismological parameters before Shidian MS5 earthquake swarm occurred in 2001, the evolution process of preparation and occurrence of moderate earthquakes for midshort and shortimminent terms are studied. The result shows:on the background of anomalies of seismicity parameters including bvalue, regulatory ratio of small earthquakes and wave velocity ratio as well as the regular migration of moderate earthquakes for middle term in Yunnan province,some midshort term anomalies such as frequency, bvalue and strain acceleration in seismogenic zone of western Yunnan appear.Mainwhile some shortimminent term anomalies such as continuous frequency increase of earthquakes with ML≥3.0 and ML≥4.0, anomaly of daily frequency of earthquakes with ML≥3.0 and notable quiescence of earthquakes with ML≥3.0 and ML≥4.0 also appear in Yunnan province. Especially the anomaly quiescence of earthquakes with ML≥3.0 and ML≥4.0 gives obvious mark of imminent information. A preliminary discussion on how to distinguish a single earthquake during the continuous occurrence of moderate earthquakes is made.