An $ML$ 5.7 earthquake struck Xingwen County, Sichuan Province, China (28.239° N, 104.922° E) on 16 December 2018. More than two weeks later on 3 January 2019, an $ML$ 5.3 earthquake occurred 8 km to the west. These were the largest and most damaging events in the Changning shale gas block and resulted in extensive damage to nearby farmhouses and other structures. Although the official hypocentral depths for both events are large than 5 km, the centroid moment tensor solutions based on the generated cut‐and‐paste method were very shallow (3 and 1.8 km for $ML$ 5.7 and 5.3, respectively). In addition, both events were very close to hydraulic‐fracturing (HF) zones of horizontal wells, in which HF was ongoing. A convening chain of evidence, including spatiotemporal correlation between earthquakes and HF zones, statistic parameters of seismicity, and estimated overpressure required to activate the unfavorably oriented source faults of the largest events, suggests that a series of earthquakes were induced by HF at a depth of $∼2.5–3km$⁠. In the Changning block, thus far, 11 $ML≥4.0$ events (including 3 $ML≥5.0$⁠) were observed since the systematic HF operation began in 2014. The Omori‐type aftershock productivity is very low as compared to normal tectonic seismicity. In addition, estimated overpressure ranged from $∼0.3$ to 5.8 MPa for $Mw>3.5$ events. The poroelastic stress changes are less than 1 MPa out of the treatment zones. Hence, overpressure‐driven reactivation of pre‐existing faults (most of them are unmapped and unfavorably oriented for slip under the present tectonic stress field) is considered to be the cause of these abnormal moderate‐size earthquakes.

The Jinshajiang fault zone is the western boundary fault of the Sichuan–Yunnan block, located east of the Qinghai–Tibetan Plateau. It is a complex tectonic suture belt with multi-phase activity and is characterized by multiple sets of parallel or intersecting faults. Using high-resolution image interpretation, seismic geological surveys, and trench studies, we examined the Holocene activity and obtained the paleoseismic sequences on the middle segment of the fault zone. Thus, we could analyze the kinematic characteristics of the fault and its potential risk of strong earthquakes. Our results indicated that the predominant movement of the fault zone was strike-slip motion. In the Jinshajiang fault zone, the Late Quaternary horizontal slip rates of the north-northeast-trending Yarigong fault and the northeast-trending Ciwu fault were 3.6 ± 0.6 mm/a and 2.5 ± 0.5 mm/a, respectively. Three paleoseismic events were identified on the Yarigong fault, dated 6745–3848, 3742–1899, and 1494–1112 cal BP, and on the Ciwu fault, constrained to 32,566–29,430, 24,056–22,990, and 2875–2723 cal BP. The last major earthquake on the Ciwu fault occurred approximately 2800 years ago; therefore, its future seismic hazard deserves attention.

The Jinshajiang fault zone is the western boundary fault of the Sichuan–Yunnan block, located east of the Qinghai–Tibetan Plateau. It is a complex tectonic suture belt with multi-phase activity and is characterized by multiple sets of parallel or intersecting faults. Using high-resolution image inter-pretation, seismic geological surveys and trench studies, we examine the characteristics of the Holocene activity on the middle segment of the fault zone. Our results indicate that the predomi-nant movement of the fault zone is strike-slip motion. In the Jinshajiang fault zone, the Late Qua-ternary horizontal slip rate of the north-northeast–trending Yarigong fault and the north-east-trending Ciwu fault are 3.6 ± 0.6 mm/a and 2.5 ± 0.5 mm/a, respectively. Three palaeoseismic events were identified on the Yarigong fault, dated 6745–3848, 3742–1899 and 1494–1112 cal BP, and on the Ciwu fault, constrained to 32,566–29,430, 24,056–22,990 and 2875–2723 cal BP. The last major earthquake on the Ciwu fault occurred approximately 2800 years ago; therefore, its future seismic hazard deserves attention.