Contributions of tides and tsunamis to formations of caldrons in the Seto Inland Sea.

Abstract

By using the results of the simulations of tides and tsunamis in the Seto Inland Sea, we estimate the maximum current speeds induced by both tides and tsunamis around about 250 caldrons, of which formation processes were considered by Yashima (1994). Estimating a correlation between maximum current speeds and the depths of the caldrons, we examine the contributions of the currents induced by tides and tsunamis to the formations of caldrons in the Seto Inland Sea. The following results are obtained. 1) Concerning the caldrons laying in the center of the straits, a comparatively high correlation is found between maximum tidal currents and the depths of caldrons. This supports Yashima (1994), which concluded most of caldrons in the Seto Inland Sea were created by tidal erosion. 2) We find that the secondary undulations are generated by the resonance of tsunamis in some areas in the Seto Inland Sea, and strong currents occurred around the nodes of the undulations, which are usually formed at the mouths of small bays. It is high likely that the caldrons at these points were created by the strong currents of tsunamis. 3) The currents induced by both tides and tsunamis are weak around the caldrons located off the capes.