2007年宁洱6.4级地震研究

Research on the 2007 Ning′er M6.4 Earthquake

根据云南宁洱地区地质构造、历史强震资料、云南监测中心区域台及现场流动台数字化观测台网测定的2007年宁洱6.4级地震序列资料及1970年以来宁洱地区6级地震序列等,深入分析研究了宁洱地区中强地震活动规律、宁洱6.4级地震的余震时空展布以及参数变化等特征,并利用2007年宁洱6.4级地震地震现场数字化观测流动台测定的余震波资料研究了该序列地震波动力学特征。研究结果认为,宁洱6级地震活动在空间上具有较高的原地重复性,在时间上具有强弱交替活动的韵律;2007年6月3日宁洱6.4级地震的余震展布方向与穿过震区NW向宁洱断裂的走向大致一致,宁洱6.4级地震可能是由无量山断裂活动构造加剧所引起;根据2007年6月3日宁洱6.4级地震序列及历次宁洱6级地震序列时序发展特征分析研究得出,宁洱6.4级地震序列能量主要集中在震后3天内释放,4.9级以上余震发生在主震当天,地震序列早期参数和3.0级以上余震的垂直方向P波最大振幅与S波最大振幅非线性关系等显示,宁洱6.4级地震序列具有较明显的主-余震型特征。

The seismic data measured by the local stations and on the spot stations′ digital monitoring station network of Yunnan monitoring center are processed based on the geological structure of Ning′er region in Yunnan Province,the historical records of strong earthquakes and Ning′er M6.4 earthquake data in 2007 and its series of M6 since 1970s.The activity regularity of the moderate and strong earthquakes is deeply investigated,including the time-spatial distribution and parameter variation features of aftershock of Ning′er earthquake.Using the aftershock wave data measured in the same place,we also discussed the dynamic characteristics of seismic wave of this series.The results indicate that there is a higher spatial reoccurrence and time rhythm alternated from strong to weak levels in this Ning′er′s M6 seismic activity.The aftershock′s distribution of the Ning′er′s M6.4 event on June 3 2007 nearly spreads along the Ning′er N-W direction Faults across the seismic area,from which we can judge,is because of the stronger activity of Ning′er faults.From our analysis about the M6.4 event and all previous M6 events,the earthquake energy is mainly released in the first three days after this earthquake,and the M5 or M4.9 aftershocks occurred in the day of principle shock.The nonlinear relationship of the maximum amplitudes of the vertical P wave and S wave of earlier parameter of this series and the aftershocks of M≥3.0 also shows that the Ning′er earthquake series is obviously the mainshock-aftershock type.