甘肃岷县漳县Ms6.6地震前“陆态网络”基准站东西分量时序曲线异常特征研究

Study on Abnormal Features in EW Displacement before Minxian-Zhangxian M_S6.0 earthquake in Gansu

收集了甘肃岷县漳县MS6.6地震前震中附近"陆态网络"基准站GPS数据,并应用PODAP软件进行解算。结果发现震中附近大多数基准站位移三分量时间序列曲线出现突变性异常,异常分量主要为东西分量;异常出现时间集中在震前4周左右;异常幅度为10mm左右。

The China Earthquake Network Center recorded an Ms6.6 earthquake at 7：45 CST on July 22, 2013, at the boundary of Minxian and Zhangxian in Gansu province. The earthquake was located in the western region of the Qinling Mountains in southern Gansu along the north branch of the Lintan--Dangchang fault. Thirteen counties were affected in the VI degree zone and above. Immediately following this earthquake, the data from 10 Global Navigation Satellite Systems （GNSS） stations of the Crustal Movement Observation Network of China recorded from July 2, 2012, through July 4, 2013, were analyzed to determine that nine earthquakes of magnitude Ms6.0 occurred during this period in China＇s mainland and adjacent areas. Analysis revealed that the horizontal component of the displacement time series curves differed prior to and following these earthquakes. Two of the most recent earthquakes showed obvious, significant changes indi- cating that north-south component is a weaker earthquake indicator than the east-west compo- nent. Since June 1, nearly all reference stations recorded obvious changes. The variable quantities were more than 10 mm and significantly exceeded this value in two days. This large variation was particularly notable after June 23, approximately one month prior to the earthquake. Several reference stations showed significant changes in eastern displacement. The Jingning and Lanzhou stations showed changes at the same time on June 23 to June 24 with amplitudes of 18.1 mm and 20.9 mm, respectively. The Dingxi station showed a significant change on June 27 with amplitude of 22.7 mm. In comparison, changes at Dingxi, Maqu, and Qingshui stations were not significant changes between June 29 and July 5. However, stations distributed north-south frequently showed chan- ges greater than 10 mm changes, and those located farther from the earthquake＇s focus generally occurred earlier. The displacement time series did not show consistency between in east-west and north-south distribution. Not reference station registered abnormal changes in horizontal displacement before the earthquake, and the changes generally were not synchronized. Some deformation occurred on or following the earthquake that differed among stations. However, all of these precursor character- istics are considered meaningful. The displacement component alone is insufficient for determining precursor anomalies; rath- er, a combination of various observation methods and a variety of earthquake monitoring data are necessary for identifying anomalies, which should include integrated information various different angles. Although changes were detected in the results, such anomalies weakly suggest the seis- mogenic moment of an upcoming earthquake and do not clearly to confirm earthquake location. To address this challenge, further research and in-depth analysis are required for earthquake pre- diction.