青海玛多M7.4地震前洞体应变异常分析

2021年5月22日,在青海省玛多县发生了M7.4地震。研究选用5月1日至22日同仁台、宕昌台、武都台和姑咱台洞体应变观测资料,采用多尺度小波分解方法处理。结果显示,在尺度11,较近的两个台北南向在震前均出现幅度明显增大的现象,总体显示出震中距越小形变幅度越大的特征。对于5月份的10日至14日和16日至20日两个时段的矢量运动轨迹进行比较,显示出明显不同的运动特征。另外,大武台和合作台地磁垂直分量的多尺度小波分解也表明,在尺度18,同样时段内也存在振幅增大的现象,这也印证了应变异常的可靠性。我们认为这个应变异常现象和其后发生的玛多M7.4地震有关,是青藏块体东向推挤的结果。结合其他学者的研究结果,我们推测这可能与震中区下方存在的高导层的运动变化有关联。但这只是一个初步研究,其详细的孕震环境和机理尚需进一步研究认识。

Anomalies of cave strain observation before the MaduoM7.4 earthquake in Qinghai Province

On May 22, 2021, an M7.4 earthquake occurred in Maduo County, Qinghai Province. In this study, the cave strain observation data of Tongren, Tangchang, Wudu, and Guza stations from May 1 to 22 were selected and processed with the multi-scale wavelet decomposition method. The results showed that at scale 11, the amplitude of NS components at two close stations increased significantly before the earthquake. Generally, the smaller the epicentral distance is, the larger the deformation amplitude is. There were obviously different characteristics of the vector trajectories during May 10-14 and 16-20. In addition, the multi-scale wavelet decomposition of geomagnetic vertical component at Dawu and Hezuo stations showed that the amplitude increased in the same period (scale 18), which also confirmed the reliability of the strain anomaly. We believe that this strain anomaly is the eastward pushing result of the Qinghai-Tibet block, and is related to the consequent MaduoM7.4 earthquake. Combined with the research results of other scholars, we inferred that this may be related to the movement of the high conductive layer beneath the epicenter. However, this is only a preliminary study, and the detailed seismogenic environment and mechanism need to be further studied.