Seismicity Induced by Salt Mine Water Injection in the Changning Area, China: Insights from Dense Linear Array Imaging

Abstract The Changning region in the southeastern Sichuan basin, China, has experienced a significant increase in seismicity, including several moderate-to-strong earthquakes, since 2006. One prevailing hypothesis suggests that this increasing seismicity, including the Ms 6.0 Changning earthquake, is linked to local salt mining activities. However, the existing velocity structure models for the Changning earthquake area suffer from low resolution, limiting our understanding of the underlying causes of the increased seismicity. In this study, we conducted a detailed survey using a dense linear array with a station spacing of approximately 50 m in the Changning mainshock area. Using ambient noise tomography, we generated a high-resolution shear-wave velocity profile that reveals a low-velocity anomaly extending approximately 4 km horizontally and 2 km vertically near the salt mining region, likely induced by water injection during salt extraction. This anomaly shows a strong spatial correlation with historical seismic events, confirming the potential link between salt mining and the observed increase in seismicity. Furthermore, the low-velocity anomaly intersects with the seismogenic fault responsible for the Ms 6.0 Changning earthquake, providing critical seismological evidence of water injection-induced seismicity. These findings provide valuable insights into the mechanisms driving high-frequency seismic activity in the Changning area.