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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. Plain Language Summary: The number of earthquakes induced by the process of shale gas extraction through hydraulic fracturing (HF) has been increasing across the globe, with dozens of M > 4 events reported by the end of August 2021. Although most case studies on HF‐induced seismicity are from the United States and Canada, the southwestern Sichuan Basin (China), located to the southeast of the Tibetan Plateau, is another region with notable seismicity linked to HF operations, including dozens of moderate‐to‐large earthquakes. We here focus on the three largest Mw ≥ 4.7 earthquakes that occurred within the Changning shale gas field up to now. We use geodetic techniques to measure ground deformation caused by the three earthquakes and to further infer their ruptures at depth. Our results reveal that the three earthquakes occurred on shallow faults intersecting with horizontal HF wells, with little‐to‐no slip in the crystalline basement below the depth of 3 km. These questions the common theme of HF‐induced earthquakes having hypocenters proximal to basement rock, presumably associated with basement‐rooted faults, and suggests that the potential for ground shaking of HF‐induced earthquakes is more significant than previously understood. Key Points: The three events ruptured shallow faults within sedimentary formations above the shale gas bed rather than basement‐rooted faultsThe faults of the three events intersect with horizontal hydraulic fracturing wells and were likely reactivated by direct fault‐zone pressurizationHigh HF‐induced seismicity rate in the Changning area links to the proximity to a triple junction region with relatively high tectonic strain accumulation rates [ABSTRACT FROM AUTHOR]

Abstract Knowledge of how strain is partitioned and accommodated in crustal shortening provides fundamental constraints on evaluating tectonic models of orogenic plateaus. A number of tectonic models have been proposed for the central Longmen Shan along the eastern Tibetan Plateau margin, including mid-crustal channel flow, upper crustal shortening, and whole crust shearing. However, it remains controversial whether these models work in the Min Shan – northern Longmen Shan area, and if so, how the models function in three dimensions. One straightforward test is to evaluate the timing and rate of uplift on the principle crustal faults. Here we present 36 fission track dates from this region. Our data show that the southeastern Min Shan has experienced the most rapid exhumation in this area since the late Miocene, due to slip along the Huya thrust and coeval northwestward tilting of the Min Shan fault block. Further, we identify a "maximum exhumation belt" (MEB) along Min Shan and Longmen Shan that is characterized by the greatest amount of exhumation in the late Cenozoic and the formation of 5000+ m peaks along the eastern Tibetan Plateau margin. Interestingly, the MEB overlies the "Moho ramp" between the Tibetan Plateau and the Sichuan Basin. The parallelism between the MEB and the Moho ramp leads us to a crustal-scale tectonic model, in which the Tibetan upper crust undergoes shortening and thrusting and the lower crust undergoes pure-shear thickening. Moreover, a ∼15° angle exists between the trend of the MEB and that of the Longmen Shan, implying that the Longmenshan thrust belt is a reactivated structure, which explains the along-strike variations of fault kinematics and activity. We conclude that the eastern Tibetan crust is partially decoupled, and future studies need to quantify strain partitioning in both the upper and the lower crust during continental orogenesis. Highlights • Rapid exhumation (∼0.9 mm/yr) and northwestward tilting occurred in Min Shan. • A maximum exhumation belt (MEB) overlaps the Moho ramp along the plateau margin. • The parallelism implies deep crustal deformation influences surface exhumation. • The MEB has ∼15° angle with the Longmen Shan, indicative of tectonic reactivation. • Partially decoupled upper and lower crust and a fully coupled crust and mantle. [ABSTRACT FROM AUTHOR]

In the epicenter of the Lushan M7.0 earthquake there are several imbricate active reverse faults lying from northwest to southeast, namely the Gengda-Longdong, Yanjing-Wulong, Shuangshi-Dachuan and Dayi faults. Emergency field investigations have indicated that no apparent earthquake surface rupture zones were located along these active faults or their adjacent areas. Only brittle compressive ruptures in the cement-covered pavements can be seen in Shuangshi, Taiping, Longxing and Longmen Townships, and these ruptures show that a local crustal shortening occurred in the region during the earthquake. Combining spatial distribution of the relocated aftershocks and focal mechanism solutions, it is inferred that the Lushan earthquake is classified as a typical blind reverse-fault earthquake, and it is advised that the relevant departments should pay great attention to other historically un-ruptured segments along the Longmenshan thrust belt and throughout its adjacent areas. [ABSTRACT FROM AUTHOR]