32. Sponge fault structural model to elucidate the effects of snow load, sea level and air pressure on crustal pumping movement activated by global warming

Abstract

The spongy fault zones containing a large amount of water are supposed to have been involved in the frequent occurrence of earthquakes due to global warming. After the land uplift in Japan stopped in 1985, the sea level has risen at an average rate of 2.8 mm/year, and small and medium-sized earthquakes of M5 or less have occurred frequently in proportion to the sea level. On the other hand, it was suggested that the crustal pumping motion that causes large earthquakes of M5 or more are caused by the highly pressurized water in the fault zone by the snow load, to rise up the Tohoku region after snowmelt. Therefore, we analyzed changes in land height, snow cover and sea level changes in various parts of Japan, and found that the crustal pumping movement is promoting the starting off the coast of Sanriku and moving eastward while rising onto the Pacific plate. Based on this mechanism, we improved the model for estimating the amount of crustal deformation that triggers large earthquakes, and investigated earthquake prediction methods.