Shallow slip of blind fault associated with the 2019 Ms6.0 Changning earthquake in fold-and-thrust belt in salt mines of Southeast Sichuan, China
Journal
Geophysical Journal International
Journal Volume
224
Journal Issue
2
Pages
909-922
Date Issued
2021
Author(s)
Abstract
An earthquake with a magnitude of Ms 6.0 and shallow focal depth of ?4 km struck the Changning county, Sichuan province, China on 2019 June 17. The hypocentre is located in the fold-and-thrust belt with plentiful shale gas and salt mine resources. One hypothesis is that the shallow fault could be affected by the artificial pressure water injection including the disposal of wastewater, fracking shale gas extraction and salt mining in Changning area. In this study, SAR (Synthetic Aperture Radar) images, historical earthquakes, aftershocks and seismic reflection data were collected to jointly investigate the characteristics of the 2019 Changning earthquake. The source model inferred from the InSAR coseismic deformation observation reveals that the 2019 Changning earthquake is attributed to a blind fault dipping to southwest with dominant thrust and sinistral strike slip. Moreover, a small shallow fault developing within the Changning anticline was triggered by the main shock, which contributed to the surface displacements as observed in the north of the epicentre. The estimated maximum slip of.49 m is located at the depth of ?1.9 km, ?9 km northwest of the epicentre. The Coulomb failure stress change caused by the previous two large earthquakes, which occurred in the hydraulic fracturing area, suggesting that they have little effect on the initial rupture of the 2019 Changning earthquake. Despite this, they have a positive triggering effect on the fault rupture in the northwest of the seismogenic fault. In addition, the analysis on the relation between the positive Coulomb failure stress change and the aftershocks suggests that the aftershocks may have different motion patterns from the main shock. The analysis also shows the earthquakes occurrence in the seismogenic zone may be affected by the high pore pressure due to the long-term injection of salt mining for more than three decades. ? 2020 The Author(s) 2020. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Subjects
Fault slips; Hydraulic fracturing; Radar reflection; Salt mines; Shale gas; Strike-slip faults; Synthetic aperture radar; Wastewater disposal; Coseismic deformation; Coulomb failure stress; Fold-and-thrust belts; Historical earthquakes; SAR(synthetic aperture radar); Seismic reflection data; Seismogenic faults; Surface displacement; Earthquakes; earthquake event; fault slip; faulting; fold and thrust belt; high pressure; radar interferometry; remote sensing; salt; seismic source; seismicity; synthetic aperture radar; tectonics; Changning [Sichuan]; China; Sichuan
Type
journal article