云南区域强震活动中短期异常的共性特征及应用研究*

(1.云南省地震局,云南 昆明 650224; 2.江川县防震减灾局,云南 江川 652600)

云南强震; 异常特征; 预测判据; 异常机理

Common Characteristics and Application Research on Periodic Anomaly before Strong Earthquakes in Yunnan Province
FU Hong1,HONG Min1,WANG Guangming1,HU Xiaojing1,LI Xiang2,LI Zhirong1,LIU Zifeng1

(1.Yunnan Earthquake Agency,Kunming 650224,Yunnan,China)(2.Earthquake Prevention and Mitigation Office,Jiangchuan 652600,Yunnan,China)

Yunnan strong Earthquake; anomaly sharacteristics; rorecast criterion; anomaly mechanism

备注

通过梳理云南区域M≥6.8强震前,地震活动和形变、地下流体、GNSS等定点地球物理观测资料,发现:1900年以来86%的M≥6.8地震前,震中附近150 km范围内的区域,5.0级以上中等地震有7~14年的平静,平静后部分强震前3~4年会出现1次中等地震活动,继续平静再发生主震; 部分强震5,6级中等地震平静后又持续活动多年,但主震前1~3年中等地震在主震附近出现丛集并形成条带; 1971年以来所有M≥6.8地震前,震中附近2°×2°范围或强震所处的小构造区,震前1~2年4级地震频度显著增加,b值由高降低且△b≥0.3; 震前1年内形变、流体部分测点出现显著的大幅度破年变异常; 70 d内有准同步的突变异常,且有1~2项变化幅度是近10年观测以来最大幅度; 2014年鲁甸6.5和景谷6.6级地震前1个月,GNSS观测到了震中附近区域显著的挤压增强现象,景谷地震后至2019年底,均未见云南有显著挤压增强区。利用这些强震前的异常特征,构建了云南区域强震的中短期预测判据,最后对部分观测现象可能的机理进行了讨论。

Based on comprehensive analysis of the geophysical observation data of seismicity,deformation,underground fluid,and GNSS in a few specific stations before the M≥6.8 earthquakes in Yunnan region,we conclude that since 1900,before occurrence of 86% M≥6.8 earthquakes,there was a seismic quiescence of M>5 earthquakes,which last 7 to 14 years,in areas within 150 km of epicenter.After the quiescence,a moderate earthquake usually disturbed the quiet period 3~4 years before the occurrence of the coming strong event,then another quiet period continued until the main shock occurs.After occurring of a few strong earthquakes,years-quiet-period of moderate earthquakes lasted many years,while moderates earthquake clustered and belted 1~3 years before the main shock.Since 1971,in the 2°×2° epicenter zone or in the strong epicenter zone,frequentness of M>4 earthquakes have increased abruptly and b value has decreased from a high value to a low value,1~2 years before all the M>6.8 earthquakes.Nearly one year before the main earthquake,in specific stations,the deformation and fluid observation data anomalies occurred distinctly,also quasi synchronous mutation anomalies in 70 days,among them 1~2 changes are the largest values in the past 10 years.In 2014,a significant compression enhancement in the vicinity of the epicenter was observed just one month before the Ludian MS6.5 and Jinggu MS6.6 earthquakes.Furthermore,from the occurrence of the Ludian MS6.5 earthquake to the end of 2019,there was no significant compression enhancement in the Yunnan region.Based on the abnormal characteristics before strong earthquakes,the medium and short term prediction criteria of strong earthquakes in Yunnan region are constructed.Finally,the possible mechanism of some observation phenomena is discussed.