To study the crustal movement in the vicinity of the epicenter before the Zhangye MS5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field analysis based on the CMONOC data observed from GPS. The baseline time series between two continuous GPS stations and the strain time series of an area among several stations are analyzed in the epicenter area. The resulting time series of baseline azimuth around the epicenter reflects that the energy of the fault in the northern margin of Qilian Mountain is accumulated continuously before 2017. Besides,the movement trend of azimuth slows down after 2017,indicating the stress accumulation on both sides of the seismogenic fault zone has reached a certain degree. The first shear strain and EWdirection linear strain in the epicentral area of the Zhangye MS5.0 earthquake remain steady after 2017,and the surface strain rate decreases gradually after 2016. It is illustrated that there is an obvious deformation loss at the epicentral region three years before the earthquake,indicating that a certain degree of strain energy is accumulated in this area before the earthquake.
MA HaipingWANG QianZHANG BoWU ShanyiWANG PengtaoDOU XiyingLI Minjuan
In order to study the characteristics of crustal deformation around the epicenter before the 2016 M_S6. 4 Menyuan earthquake,the GPS continuous stations of the period from 2010 to 2016 were selected according to the observation data of the tectonic environment monitoring network in Chinese Mainland. The deformation characteristics of the crust before the earthquake were discussed through inter-station baseline time series analysis and the strain time series analysis in the epicentral region. The results show that a trend turn of the baseline movement state around the epicenter region occurred after 2014,and the movement after 2014 reflects an obvious decreasing trend of compressional deformation.During this period,the stress field energy was in a certain accumulation state. Since the beginning of 2014,the EW-component linear strain and surface strain rate weakened gradually before the earthquake. It shows that there was an obvious deformation deficit at the epicentral area in the past two years,which indicates that the region accumulated a high degree of strain energy before the earthquake. Therefore,there was a significant background change in the area before the earthquake. The results of the study can provide basic research data for understanding the seismogenic process and mechanism of this earthquake.
采用CAP(Cut and Paste)方法反演了2016年1月21日青海门源MS6.4地震的震源机制解,其最佳双力偶解节面I走向339°,倾角49°,滑动角111°:节面Ⅱ走向129°,倾角45°,滑动角68°,矩震级MW5.92,矩心震源深度约为9km,地震破裂类型为逆冲型地震。结合余震序列展布及震区的活动构造特征,判定发震断层面为节面I,推测此次地震的发震断裂为冷龙岭断裂。
