Coseismic Water-Level Changes in the Same Well Induced By Teleseismic Waves of Three Huge Earthquakes

Abstract:

Three huge earthquakes (the 2007 M_w 8.4 Sumatra, the 2008 M_w 7.9 Wenchuan, and the 2011 M_w 9.0 Tohoku earthquakes) happened in recent years induce obvious coseismic water-level increases at far fields (epicentral distances >1000 km) in the Fuxin well located in the Fuxin city of Liaoning province, northeastern China (the well with the observation of both water levels and volume strains). We compare water levels and volume strains for these earthquakes. A comprehensive analysis for the mechanism of far-field coseismic water-level changes is performed by analyzing the in-situ permeability, Skempton’s coefficient B, and together with the broadband seismograms from a nearby station. We find that an undrained consolidation with a decreasing permeability induced by the shaking of teleseismic waves is observed in the far field. By the in-situ observation for different earthquakes, shaking of teleseismic waves can induce consolidation or dilatation in the aquifer of Fuxin well, both of them being able to enhance permeability and thus to build a new pore-pressure equilibrium system between the Fuxin well and the nearby Sihe reservoir (150 m away from the Fuxin well). The resulting interstitial fluid flow across the region increases coseismic water levels in the aquifer of Fuxin well.