Abstract
On August 8, 2017, the Jiuzhaigou Mw 6.5 earthquake occurred in Sichuan province, southwestern China, along the eastern margin of the Tibetan Plateau. The epicenter is surrounded by the Minjiang, Huya, and Tazang Faults. As the seismic activity and tectonics are very complicated, there is controversy regarding the accurate location of the epicenter and the seismic fault of the Jiuzhaigou earthquake. To investigate these aspects, first, the coseismic deformation field was derived from Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) measurements. Second, the fault geometry, coseismic slip model, and Coulomb stress changes around the seismic region were calculated using a homogeneous elastic half-space model. The coseismic deformation field derived from InSAR measurements shows that this event was mainly dominated by a left-lateral strike-slip fault. The maximal and minimal displacements were approximately 0.15 m and − 0.21 m, respectively, along line-of-sight observation. The whole deformation field follows a northwest-trending direction and is mainly concentrated west of the fault. The coseismic slip is 28 km along the strike and 18 km along the dip. It is dominated by a left-lateral strike-slip fault. The average and maximal fault slip is 0.18 and 0.85 m, respectively. The rupture did not fully reach the ground surface. The focal mechanism derived from GPS and InSAR data is consistent with the kinematics and geometry of the Huya Fault. Therefore, we conclude that the northern section or the Shuzheng segment of the Huya Fault is the seismogenic fault. The maximal fault slip is located at 33.25°N and 103.82°E at a depth of ~ 11 km, and the release moment is approximately 6.635 × 1018 Nm, corresponding to a magnitude of Mw 6.49, which is consistent with results reported by the US Geological Survey, Global Centroid Moment Tensor, and other researchers. The coseismic Coulomb stress changes enhanced the stress on the northwest and southeast edges of the northern extension of the Huya Fault. Seismic risks cannot be ignored in the future although aftershocks are fewer in number in these regions.
Highlights
A strong earthquake occurred on August 8, 2017, in Jiuzhaigou county of the Aba region in northern Sichuan province, China, resulting in 25 deaths, 525 injuries, and extensive damage to buildings
Precise determination of the position of the seismogenic fault of the Jiuzhaigou Mw 6.5 earthquake and its features can serve as an important clue for the understanding of tectonic characteristics and seismic activities of the region
Because the epicenter position determined by seismology is not accurate (Zheng and Xie 2017), it is very important to determine the precise position of the epicenter using geodetic observations
Summary
A strong earthquake occurred on August 8, 2017, in Jiuzhaigou county of the Aba region in northern Sichuan province, China, resulting in 25 deaths, 525 injuries, and extensive damage to buildings. Using horizontal GPS velocities between 2013 and 2015 from the latest data of the Crustal Movement Observation Network of China (CMONOC) (Fig. 1a), we inverted the slip rates across the Huya Fault using a profile projection method. The coseismic deformation field of LOS obtained from the ascending track data (Fig. 2a, c) presents a shape of a long flat oblate with the long axis trending to the NW with a maximal uplift and subsidence of 0.07 and 0.21 m, respectively. The deformation on both sides of the fault is asymmetric. Where Δτ is the change in shear stress on the fault plane (the direction of the fault slipping is positive); Δσn is the change in normal stress
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