GPS测定的四川九寨沟MW6.6地震同震形变

2017年8月8日四川阿坝州九寨沟发生M_W6.6地震,震源机制解显示该地震为左旋走滑型地震。对震中周围的GPS连续站观测资料进行处理,获得高频GPS动态形变和静态同震水平位移。震中100km范围内四川松潘和甘肃武都站观测到1 Hz动态形变。距离震中约69km的松潘站观测的同震水平位移为7.4mm。根据少量的GPS静态同震位移反演的同震破裂模型显示本次地震的最大滑动量为376mm,地震矩为7.25×1018 N·m,等效矩震级为M_W6.6。正演计算的同震三维形变场显示本次地震的最大水平位移可达4~5cm,垂直位移呈四象限分布,最大可达1.5cm,区域内10个流动GPS站可观测到同震形变。

Co-seismic Deformation Associated with the Jiuzhaigou, Sichuan MW6.6 Earthquake by GPS Data

The M_W6.6 earthquake occurred in Jiuzhaigou County, Sichuan Province, on August 8, 2017. The focal mechanism solution shows that the earthquake was a left-lateral strike-slip earthquake. In this study, the observation data from GPS continuous stations around the epicenter are processed to obtain a high-rate GPS dynamic deformation and static co-seismic horizontal displacement. Through 1 Hz GPS data measurements, dynamic deformation is only observed at the Songpan station in Sichuan Province and Wudu station in Gansu Province within 100 km of the epicentre. The co-seismic horizontal displacement observed by the Songpan station, the nearest continuous station to the epicenter, is 7.4 mm. The co-seismic rupture model inferred based on a small amount of GPS static co-seismic displacement shows that the maximum slippage of the earthquake is 376 mm, the seismic moment is 7.25×10¹⁸ N·m, and the equivalent moment magnitude is M_W6.6. The co-seismic three-dimensional deformation field obtained by forward calculation shows that the maximum horizontal displacement of this earthquake can reach 4~5 cm, and the vertical displacement can reach a maximum of 1.5 cm in a four-quadrant distribution. The co-seismic deformation can be observed in 10 mobile GPS stations in the region.