Permeability enhancement in the aquifer of Fuxin well in geothermal area of northeastern China induced by low-frequency teleseismic waves of the 2011 [M.sub.w] 9.0 Tohoku earthquake

The [M.sub.w] 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 x [10.sup.-2] J/[m.sup.3] 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 x [10.sup.-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. Keywords: Permeability variation Teleseismic waves Mw 9.0 Tohoku earthquake Coseismic water level changes Volume strain variation