The 2019 Mw 5.8 Changning, China earthquake: A cascade rupture of fold-accommodation faults induced by fluid injection

Abstract

Industrial production activities associated with salt mining, hydraulic fracturing, or geothermal exploitation can induce pore pressure and stress field changes, thus inducing seismic activity. Most of the events are not disastrous due to limited energy radiated. Here we report a Mw 5.8 damaging event that occurred in Changning, China on June 17, 2019, probably the largest induced event by industrial exploitation ever recorded. The earthquake is located within the Changning anticline, and it raises great concerns on why and how the event occurred in a relatively quiescent area in terms of tectonic activity. Moreover, it has been debated whether this earthquake ruptured solely on the fold-accommodation faults or also involved a deep-rooted fault under the anticline. By using InSAR data from two satellites, we investigate the detailed rupture and slip pattern of this earthquake. We propose a cascade rupture mode of the fold-accommodation faults, through poroelastic modeling of excess pore pressure by fluid injection and pumping operations and static Coulomb stress calculation on the pre-stressed faults. We argue that water injections may have triggered this event. The result highlights the importance of reassessing seismic hazard over similar tectonic environments with intensive industrial exploitation.