From Quiescence to Chaos: Triggering of Two M5 Earthquakes in the Weiyuan Shale Gas Field, China
Description:
Understanding how hydraulic fracturing triggers earthquakes—particularly rare but destructive events—is critical for mitigating induced-earthquake hazards. Here, we document a clear transition from fault quiescence to mechanical chaos preceding two ML ≥ 5 earthquakes (ML 5.6 in September and ML 5.4 in December 2019) in the Weiyuan shale gas field, China, where hydraulic fracturing targeted the Silurian Longmaxi Formation (Shale strata I).
From 2015 to early 2018, extensive hydraulic fracturing was conducted at multiple well pads surrounding the target fault zone. During this phase, the fault zone remained largely quiescent, despite the migration of low-magnitude (ML < 3) seismicity toward the fault. This apparently “lazy” fault behavior fundamentally changed following direct injection into the fault zone at the H39 platform. Fluids migrated downward from shale strata I into the Cambrian Jiulaodong Formation shale (shale strata II, ~460 m thick), ultimately triggering the ML 5.6 earthquake in September 2019 after a prolonged 11-month preparatory phase, with the rupture occurring beneath the thick shale strata II.
Seismicity induced by injection at the H39 platform also migrated toward the hypocenter of the December ML 5.4 earthquake but stalled ~1 km from the hypocenter. The ML 5.4 event occurred during hydraulic fracturing at the nearby H50 platform. We observed linear seismicity migrate towards the ML 5.4 hypocenter, suggesting elevated pore pressure triggered the second event. Estimated Coulomb stress from previous ML 5.6 event is -0.18 MPa, indicating limited static stress transfer impact in earthquake initiation. In contrast to the earlier earthquake, the rupture of the ML 5.4 event occurred above shale strata II, suggesting that this thick shale layer acted as a barrier that inhibited rupture propagation in both events.
A comparison of triggered seismicity within and outside the fault zone reveals distinct diffusion behaviors and bounded/unbounded magnitude growth, underscoring key controls on induced-earthquake hazards and providing important implications for seismic hazard assessment in shale gas fields.
Session: From Drilling to Ground Shaking: Mechanisms, Monitoring and Mitigation of Induced Earthquakes [Poster]
Type: Poster
Date: 4/17/2026
Presentation Time: 08:00 AM (local time)
Presenting Author: Jinping Zi
Student Presenter: No
Invited Presentation:
Poster Number: 103
Authors
Jinping Zi Presenting Author Corresponding Author zijinping@link.cuhk.edu.hk Chinese University of Hong Kong |
Hongfeng Yang hyang@cuhk.edu.hk Chinese University of Hong Kong |
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From Quiescence to Chaos: Triggering of Two M5 Earthquakes in the Weiyuan Shale Gas Field, China
Category
From Drilling to Ground Shaking: Mechanisms, Monitoring and Mitigation of Induced Earthquakes