基于GNSS的2023年2月23日塔吉克斯坦M_(S)7.2地震前异常资料变化特征研究

STUDY ON ANOMALY DATA VARIATION CHARACTERISTICS BEFORE TAJIKISTAN M S7.2 EARTHQUAKE ON FEBRUARY 23,2023 BASED ON GNSS

为了进一步探究中强地震发生前GNSS坐标时序中是否存在中短期异常现象,通过分析2023年2月23日塔吉克斯坦M_(S)7.2地震前后中国大陆构造环境监测网络(简称:“陆态网络”)塔什库尔干、布伦口GNSS基准站观测资料的变化特征,发现该地震震前塔什库尔干、布伦口均出现较为明显的GNSS基准站时间序列异常现象,震前EW向存在趋势性W向运动,震后E向加速;震前NS向趋势性S向运动,临震前状态快速改变,布伦口在震后还显示出7.3 mm的EW向永久性形变,研究结果表明GNSS在地震发生短临阶段具有重要的预测意义。与2015年12月7日塔吉克斯坦M S7.4地震进行对比发现,两次M S≥7.0地震对塔什库尔干、布伦口基准站的影响差异较大。2015年12月7日塔吉克斯坦M S7.4地震为左旋走滑,影响方向主要为NE向,而2023年2月23日塔吉克斯坦M_(S)7.2地震为右旋走滑,影响方向主要为SE向。震前基线均有挤压缩短的前兆异常显示。梳理站点异常出现情况,发现异常持续时间越长、异常出现次数越多,发震震级可能越大。

In order to further explore whether there are short-term and medium-term anomalies in the GNSS coordinate time series before the occurrence of moderate earthquakes,the variation characteristics of the observation data of GNSS reference stations in Tashkurgan and Bulunkou of China mainland tectonic environment monitoring network before Tajikistan M_(S)7.2 earthquake on February 23,2023 are analyzed.It is found that there are obvious time series anomalies of GNSS reference stations in Tashkurgan and Bulunkou before the earthquake.Before the earthquake,there is a trend of W-direction movement in EW direction.After the earthquake,the E-direction accelerates,and the NS-trending S-direction movement before the earthquake.The state changes rapidly before the earthquake.After the earthquake,Bulunkou also shows a permanent deformation of 7.3 mm in EW direction.The results show that GNSS has important predictive significance in the short-term and imminent stage of earthquake.Compared with in Tajikistan M S7.4 earthquake on December 7,2015,it is found that the influence of two earthquakes with magnitude greater than 7 on the base stations of Tashkurgan and Bulunkou is quite different.On December 7,2015,Tajikistan M S7.4 earthquake was left-lateral strike-slip,and the direction of influence was mainly NE.On February 23,2023,Tajikistan M_(S)7.2 earthquake was right-lateral strike-slip,and the direction of influence was mainly SE.The baseline before the earthquake showed all the precursory anomalies.By combing the anomaly occurrence of the site,it is found that the longer the anomaly duration and the more the number of anomaly occurrences,the greater the magnitude of the earthquake may be.