2014年云南地区GNSS最大剪应变格网时序异常与M≥6.0地震关系分析

基于2014年云南地区28个GNSS连续跟踪站30 s采样率的数据,以震前3个月为时间尺度、1个月为窗长,提取最大剪应变格网时间序列。对去除趋势项后的最大剪应变时间序列,设定2倍标准差作为异常阈值,以2014年盈江6.1级、鲁甸6.5级和景谷6.6级地震为样本,对地震孕育过程中最大剪应变格网时序异常与M≥6.0地震的关系进行分析。结果表明,2014年云南地区GNSS最大剪应变格网时序异常分布与上述3个地震存在较好的对应关系,震前短期内最大剪应变异常格网集中分布于震中附近区域,且存在震前增强、震后快速消失的现象;最大剪应变异常格网分布相对集中的区域可作为预报M≥6.0地震发生地点的参考性指标。最大剪应变综合指标值预测结果显示,本次预测地震数4个,成功预报地震数3个,漏报数0个,虚报地震数1个(指标出现而未发生地震),准确率为75%。从空间角度来看,3次地震的震中都位于异常格网边缘,表明最大剪应变异常区边缘可能更加危险。

Analysis of the Relationship between GNSS Maximum Shear Strain Grid Time Series Anomaly and M≥6.0 Earthquakes in Yunnan Region, 2014

Based on the data of 30 s sampling rate of 28 GNSS continuous tracking stations in Yunnan in 2014, we extract the maximum shear strain grid time series from the 3 months before the earthquake as the time scale and 1 month as the window length. For the maximum shear strain time series after the trend term is removed, two standard deviations are set as the abnormal threshold. Taking the 2014 Yingjiang 6.1, Ludian 6.5 and Jinggu 66 earthquakes as samples, the relationship between the maximum shear strain grid timing anomaly and the M≥6.0 earthquake during the earthquake incubation is analyzed. The results show that the anomalous distribution of GNSS maximum shear strain grid time series in Yunnan has a good correlation with Yingjiang 6.1, Ludian 6.5 and Jinggu 66 earthquakes in 2014. The maximum shear strain anomaly grid, in the short-term before the earthquake, is concentrated in the vicinity of the epicenter, and there is a phenomenon of pre-earthquake enhancement and rapid disappearance after the earthquake. The area where the maximum shear strain anomaly grid distribution is relatively concentrated can be used as a reference index for the future occurrence of M≥6.0 earthquakes. The maximum shear strain comprehensive index value prediction results show that the number of predicted earthquakes is 3, and 3 earthquakes are successfully predicted, 0 are missing, and 1 is falsely reported (the indicator appears without earthquake), and the accuracy rate is 75%. From a spatial point of view, the three earthquake epicenters are located at the edge of the anomalous grid, indicating that the edge of the maximum shear strain anomaly may be more dangerous.