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Three Mw ≥ 4.7 earthquakes within the Changning (China) shale gas field ruptured shallow faults intersecting with hydraulic fracturing wells

February 14, 2022

From 2017 to 2019, three destructive earthquakes (27 January 2017 Mw 4.7, 16 December 2018 Mw 5.2, and 3 January 2019 Mw 4.8) occurred in the Changning shale gas field in the southwest Sichuan Basin, China. Previous seismological studies attributed these events to hydraulic fracturing (HF), but were unable to identify the causative seismogenic faults and their slip behaviors. Here, we use Sentinel-1 synthetic aperture radar data to measure surface deformation triggered by the three events and conduct geodetic inversions to characterize their rupture models. The resulting coseismic interferograms show prominent surface deformation with the maximum line-of-sight displacements of up to 4 cm. The inversion results show that all three earthquakes mainly ruptured sedimentary formations above the shale gas bed, in the upper 3 km of the crust, with slip magnitudes ranging from 8.5 to 15 cm, and stress drops ranging from ∼1.8 to ∼3.3 MPa. Their source faults intersect with horizontal HF wells, but do not root in the crystalline basement. Combined with the reported difficulty of increasing HF operation pressures prior to the three events, we argue that they were most likely induced by direct injection of pressurized fluids into the fault zones. Crustal deformation patterns inferred from regional topography and GPS velocities highlight that the Changning field is located within a triple junction region near the southeastern margin of the Tibetan Plateau with large deformation gradients; such conditions are not only favorable to the development of critically stressed faults, but also facilitate the occurrence of at least moderate magnitude earthquakes.

Citation Information

Publication Year 2022
Title Three Mw ≥ 4.7 earthquakes within the Changning (China) shale gas field ruptured shallow faults intersecting with hydraulic fracturing wells
DOI 10.1029/2021JB022946
Authors Shuai Wang, Guoyan Jiang, Xinglin Lei, Andrew Barbour, Xibin Tan, Caijun Xu, Xiwei Xu
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research B: Solid Earth
Series Number
Index ID 70228576
Record Source USGS Publications Warehouse
USGS Organization Earthquake Science Center

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