GPS测定的2020年阿拉斯加M_(W)7.8地震震时地表动态变形及永久同震形变场

Dynamic ground deformation and coseismic deformation field during the Alaska M_(W)7.8 earthquake in 2020 by GPS data

以UNAVCO公布的阿拉斯加地区GPS 1 Hz和30 s采样观测数据为基础,采用双差定位方法分别对两种采样率的数据进行处理分析,获得2020年7月22日阿拉斯加M_(W)7.8地震震时地表动态变形及同震三维形变场。结果显示,震中270 km范围内高频GPS震时波形明显,最大振幅达600 mm。根据各个GPS站的动态形变波形振幅及响应时间认为,其振幅和响应时间受地震的破裂传播方向和场地效应影响较大。静态同震位移矢量指向震中,同震位移大小基本符合随震中距离增大而减小的特征,除站点AC13外,其中距离震中最近站点的最大水平位移达26.7 cm。GPS测定的同震形变表明,2020年阿拉斯加地震是发生在阿拉斯加阿留申俯冲大断裂的一次逆冲型地震。

The GPS 1 Hz and 30 s sampling observation data published by UNVAVCO were processed and analyzed with the double difference position method,then the dynamic ground deformation and coseismic three-dimensional deformation field during the Alaska M_(W)7.8 earthquake on July 22,2020 were obtained.The results showed that the seismic waveform of high-rate GPS within 270 km of epicenter is obvious,and the maximum amplitude is 600 mm.The amplitude and response time of dynamic deformation waveform of each GPS station are greatly affected by the rupture propagation direction of earthquake and site effect.The static coseismic displacement vector points to the epicenter,and the coseismic displacement basically decreases with the increase of epicenter distance.Except for station AC13,the maximum horizontal displacement of the station nearest to the epicenter is 26.7 cm.