Evidence of giant earthquakes and tsunamis of the seventeenth-century type along the southern Kuril subduction zone, eastern Hokkaido, northern Japan: a review

Abstract

AbstractLarge earthquakes of magnitude 7–8 occur at intervals of about 70–100 years in the southern Kuril Trench off eastern Hokkaido, northern Japan. However, especially large giant earthquakes (Mwc. 8.8) have recurred at 300–500 year intervals, and the most recent of these was in the early seventeenth century. Surveys on the Pacific coast of eastern Hokkaido have documented field evidence that includes sharp contacts of peat and mud layers, indicative of coseismic coastal uplift, and large tsunami sand layers. Several proposed fault models of the seventeenth-century giant earthquake have been tested with numerical tsunami simulations. The best of these models incorporates a multi-segment interplate earthquake (Mw 8.8) with large slip near the trench axis. The seventeenth-century giant earthquake and the 1611 Keicho Sanriku tsunami appear to have had different sources because varve counts from Lake Harutori suggest that the seventeenth-century giant earthquake occurred at c. 1637. Moreover, a consideration of regional tectonics suggests that convergence of the Kuril forearc sliver controls the current topography of eastern Hokkaido. Further progress in understanding the seismicity of this region will benefit from the combined insights of both geologists and seismologists.