Three Mw ≥ 4.7 Earthquakes Within the Changning (China) Shale Gas Field Ruptured Shallow Faults Intersecting With Hydraulic Fracturing Wells

Abstract

Of the many outstanding questions related to hydraulic fracturing (HF) induced seismicity, perhaps the most significant ones relate to determining the causative faults, the physical process driving earthquake nucleation in response to HF stimulations, and the geological conditions which make a region more-or-less susceptible to HF-induced seismicity (Atkinson et al., 2020;Schultz et al., 2020). For instance, it is thought that the largest induced earthquakes occur on basement-rooted faults, and there is debate about how significant the roles of poroelastic coupling and aseismic slip are in reactivating such faults. The Sichuan Basin (Figure 1), China, is a

Enhanced 3D velocity structure, seismicity relocation and basement characterization of Changning shale gas and salt mining regions in southern Sichuan basin

“…InSAR data have been used to infer that the Changning anticline is characterized by a single seismogenic fault (Wang S. et al, 2020), which is highly unlikely given the several faults that deform the anticline (Figure 1C). Recently, Wang et al (2022) applied InSAR inversions to define three seismogenic faults beneath the Jianwu syncline, however, they could only achieve resolution accurate to 10 by 10 km, which is lower than the 5 by 5 km resolution achieved by the earthquake tomographic inversion of this study.…”

“…The Jianwu and Luochang synclines are large with gentle intrasynclinal structural morphology and Jurassic aged topmost layer (Zuo et al, 2020). Nevertheless, two major earthquakes-2018 Xingwen M s 5.7 and 2019 Gongxian M s 5.3 shocks occurred on the Jianwu syncline (Figures 1B,C), whose seismogenic structures were well constrained by InSAR inversions (Wang et al, 2022). These synclines are mostly characterized by high-angle large scale tectonic faults and fractures that are well developed and trend mainly in the EW, NE and NNW directions (Shi et al, 2019;Wang et al, 2022).…”

“…Nevertheless, two major earthquakes-2018 Xingwen M s 5.7 and 2019 Gongxian M s 5.3 shocks occurred on the Jianwu syncline (Figures 1B,C), whose seismogenic structures were well constrained by InSAR inversions (Wang et al, 2022). These synclines are mostly characterized by high-angle large scale tectonic faults and fractures that are well developed and trend mainly in the EW, NE and NNW directions (Shi et al, 2019;Wang et al, 2022). regional stations recorded phase arrivals of about 34,296 individual seismic events within our study area from the first of January 2015 to the 31st of August 2019 (Zuo et al, 2020).…”

“…The relocation results of the Changning M s 6.0 main shock that is said to be fluid induced (Ruan et al, 2008;Zeng et al, 2014;Zhu and He, 2014;Sun et al, 2017;Lei et al, 2019b;Yi et al, 2019;Liu and Zahradnik, 2020), the associated M s > 5 aftershocks situated within the Changning salt mining area and the M s 5.3 Gongxian and M s 5.7 Xingwen earthquakes that occurred within the shale gas block are listed in Supplementary Table S1. Given the consistency in the centroid depth, spatial orientation and rupture distribution of the source faults of the 27 January 2017 M s 5.1 Xingwen earthquake, 16 December 2018 M s 5.7 Xingwen earthquake and the 3 January 2019 Ms5.3 Gongxian earthquake, determined from centroid moment solutions (Lei et al, 2017;Lei et al, 2019b;Yi et al, 2019) and recent InSAR inversions (Wang et al, 2022), we utilize their results in comparatively assessing the uncertainties of our results (Supplementary Table S2). We find that the focal depth results determined by our study agree with the shallower centroid depths obtained for these major earthquakes with thrust, strike-slip and thrust focal mechanisms, respectively.…”

Frictional stability of Longmaxi shale gouges and its implication for deep seismic potential in the southeastern Sichuan Basin

“…According to our experimental results, most shale fault slips in these shallow reservoirs should be aseismic. However, three earthquakes with Mw ≥ 4.7 have been detected in this area (2017–2019), which have been proven to be closely associated with hydraulic fracturing (Wang et al, 2022). This manifests the possibility of moderate earthquakes in shallow shale reservoirs.…”