Strain buildup in the Northeast Japan orogen with implications for gigantic subduction earthquakes

Although recent GPS observations have made it possible to detect crustal strain precisely and extensively, we have not yet observed a whole cycle of strain buildup and release in orogenic zones by any geodetic methods. From the viewpoint of earthquake forecasting, we need to extract elastic strain from GPS-derived strain data. However, we do not have any (practical) geophysical method by which to discriminate between elastic and inelastic strains from GPS data. Based on the lesson from the 2011 Tohoku earthquake of Mw 9.0, we propose here that geological methods (and ways of thinking as well) should be used to estimate inelastic strain buildup quantitatively, thereby to evaluate present-day elastic strain buildup, which may eventually cause gigantic earthquakes. We review here a case history of the 2011 Tohoku earthquake, and present a global comparison with other gigantic (Mw >= 9.0) subduction earthquakes in the world.