地震研究

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.

引言
1 资料选取
2 地震活动的阶段特征
3 强震前地球物理观测资料异常特征
4 异常特征与地震预测应用
5 结论和讨论

表1 1900年以来云南省M≥6.8地震一览表<br/>Tab.1 List of M≥6.8 earthquake in Yunnan Province since 1900

表1 1900年以来云南省M≥6.8地震一览表
Tab.1 List of M≥6.8 earthquake in Yunnan Province since 1900

图1 1900年以来云南区域M≥6.8地震前中等地震的活动图像<br/>Fig.1 Map showing moderate earthquakes distribution before M≥6.8 events since 1900

图1 1900年以来云南区域M≥6.8地震前中等地震的活动图像
Fig.1 Map showing moderate earthquakes distribution before M≥6.8 events since 1900

图2 M≥6.8强震前震中附近中等地震活动时间进程<br/>Fig.2 Diagram of temporal evolution of moderate earthquakes near the epicenter before M≥6.8 events

图2 M≥6.8强震前震中附近中等地震活动时间进程
Fig.2 Diagram of temporal evolution of moderate earthquakes near the epicenter before M≥6.8 events

图3 M≥6.8强震前中等地震丛集活动示意图<br/>Fig.3 Diagram of moderate earthquake clusters distribution before M≥6.8 events

图3 M≥6.8强震前中等地震丛集活动示意图
Fig.3 Diagram of moderate earthquake clusters distribution before M≥6.8 events

图4 强震前近场区4级地震活动增强示意图<br/>Fig.4 Diagram of frequency enhancement of MS4 earthquakes in the near field before strong earthquakes

图4 强震前近场区4级地震活动增强示意图
Fig.4 Diagram of frequency enhancement of MS4 earthquakes in the near field before strong earthquakes

图5 强震前近场区部分b值变化曲线<br/>Fig.5 Diagram of b-values variations in near field before strong earthquakes

图5 强震前近场区部分b值变化曲线
Fig.5 Diagram of b-values variations in near field before strong earthquakes

图6 强震前部分显著前兆异常<br/>Fig.6 Diagram of partial significant precursory anomalies before strong earthquakes

图6 强震前部分显著前兆异常
Fig.6 Diagram of partial significant precursory anomalies before strong earthquakes

图7 GNSS挤压增强区域示意图<br/>Fig.7 Diagram of GNSS extrusion enhanced regions

图7 GNSS挤压增强区域示意图
Fig.7 Diagram of GNSS extrusion enhanced regions

表2 云南区域强震前中短期阶段异常特征统计<br/>Tab.2 List of anomaly characteristics and the prediction criteria in short-medium term before strong earthquakes in Yunnan region

表2 云南区域强震前中短期阶段异常特征统计
Tab.2 List of anomaly characteristics and the prediction criteria in short-medium term before strong earthquakes in Yunnan region

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备注

引言

1 资料选取

2 地震活动的阶段特征

3 强震前地球物理观测资料异常特征

4 异常特征与地震预测应用

5 结论和讨论

期刊信息