Permeability enhancement in the aquifer of Fuxin Well in geothermal area of northeastern China induced by low-frequency teleseismic waves of the 2011 Mw 9.0 tohoku earthquake

Abstract

The Mw 9.0 Tohoku large earthquake induces far field (epicentral distance >1800 km) prominent coseismic water-level increase in the Fuxin well at northeastern China, which also influences volumetric strains. Different mechanisms of far-field coseismic water-level changes are analyzed by integrating these water-level/volume-strain data with broadband seismograms from a nearby station. Dilatation induced by propagating teleseismic wave (central frequency 0.02 Hz) may be the dominant mechanism of the observed water-level increases in the aquifer of Fuxin well. The dynamic energy density of ~5×10−2 J/m3 from the earthquake (computed from broadband seismograms), could be large enough to incur the far-field dilatation stress of ~0.35 MPa (with the strain variation of ̶ 3.7935×10−6) in the aquifer. The resulting enhancement in permeability by the dilatation stress can build a new pore-pressure equilibrium between the Fuxin well and the nearby Sihe reservoir (~150 m away from the Fuxin well). The induced interstitial fluid flow in the region accounts for the sustained large-amplitude coseismic water-level increase. The Fuxin well lies in the geothermal area, and this study may also has some implications for the geothermal resource exploration.