Ground uplift related to permeability enhancement following the 2011 Tohoku earthquake in the Kanto Plain, Japan

We investigated the post-seismic surface displacement of the 2011 Tohoku earthquake around the Kanto Plain (including the capital area of Japan), which is located approximately 400 km from the epicenter, using a global positioning system network during 2005–2015 and persistent scatterer interferometry of TerraSAR-X data from March 2011 to November 2012. Uniform uplift owing to viscoelastic relaxation and afterslip on the plain has been reported previously. In addition to the general trend, we identified areas where the surface displacement velocity was faster than the surrounding areas, as much as ~7 mm/year for 3 years after the earthquake and with a velocity decay over time. Local uplift areas were ~30 × 50 km and showed a complex spatial distribution with an irregular shape. Based on an observed groundwater level increase, we deduce that the local ground uplift was induced by a permeability enhancement and a pore pressure increase in the aquifer system, which is attributable to mainshock vibration.