Probing the Fault Complexity of the 2017 Ms 7.0 Jiuzhaigou Earthquake Based on the InSAR Data

Xiongwei Tang,Xiaodong Chen,Rumeng Guo,Heping Sun,Jiangcun Zhou,Jianqiao Xu

doi:10.3390/rs13081573

Abstract

On 8 August 2017, a surface wave magnitude (Ms) 7.0 earthquake occurred at the buried faults extending to the north of the Huya fault. Based on the coseismic deformation field obtained from interferometric synthetic aperture radar (InSAR) data and a series of finite fault model tests, we propose a brand-new two-fault model composed of a main fault and a secondary fault as the optimal model for the Jiuzhaigou earthquake, in which the secondary fault is at a wide obtuse angle to the northern end of the main fault plane. Results show that the dislocation distribution is dominated by sinistral slip, with a significant shallow slip deficit. The main fault consists of two asperities bounded by an aftershock gap, which may represent a barrier. In addition, most aftershocks are located in stress shadows and appear a complementary pattern with the coseismic high-slip regions. We propose that the aftershocks are attributable to the background tectonic stress, which may be related to the velocity-strengthening zones.

Highlights

On 8 August 2017, a surface wave magnitude (Ms) 7.0 earthquake occurred in Jiuzhaigou County, Aba Prefecture, Sichuan Province, China, with its epicenter at 103.82◦ E, 33.20◦ N, and a focal depth of about 20 km (Institute of Geophysics, China EarthquakeAdministration, CEA-IGP)
Because the southeasterly movement of the Bayan Har block is blocked by the North China block and the South China block, there are many broom-like branches on the eastern end of the East Kunlun fault, which intersect with the Minjiang fault and the Huya fault, resulting in a complex seismictectonic environment in this region [3]
The nearly NS-trending Minjiang fault and the southern segment of the Huya fault that are transverse compressional structures absorb the sinistral strike-slip motion of the remaining part of the East Kunlun fault, which causes the Minshan uplift on the eastern margin of the Tibetan Plateau [4,5]

Summary

Introduction

On 8 August 2017, a surface wave magnitude (Ms) 7.0 earthquake occurred in Jiuzhaigou County, Aba Prefecture, Sichuan Province, China, with its epicenter at 103.82◦ E, 33.20◦ N, and a focal depth of about 20 km (Institute of Geophysics, China EarthquakeAdministration, CEA-IGP). As of 13 August 2017, the earthquake had caused 25 deaths and severe damage to both the Jiuzhaigou scenic area and more than 70,000 structures [1]. The NWW-trending Tazang fault, the northern segment of the NNW-trending Huya fault, and other nearby branches accommodate most of the sinistral strike-slip activity of the East Kunlun fault. The nearly NS-trending Minjiang fault and the southern segment of the Huya fault that are transverse compressional structures absorb the sinistral strike-slip motion of the remaining part of the East Kunlun fault, which causes the Minshan uplift on the eastern margin of the Tibetan Plateau [4,5]

Methods

Results

Discussion

Conclusion