越前海岸にみられる海食洞と旧汀線高度について

概要

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The fault system along the Echizen Coast is considered to be one of the main active tectonic structure situated at the northern end of the Kinki Triangle, central Japan. Geological and topographical investigation show that these faults are presently in active with a vertical slip rate of more than 1m/1,000yrs. Along the coast, emergent wave cut platforms, including notches and benches, are recognized at four different levels. But these marine erosive features, especially those of upper platforms, are not in a good state of preservation by eroding and weathering. The sea cave, the cavity in the base of a sea cliff, is well able to preserve the marine erosive features, coastal sediments and shell fossils at the time. So, we investigate emergent sea caves to reexamine the paleoseismological events along the Echizen Coast. The height of the retreat point of the notch in the sea cave is almost equal to that of the notch cut into the reef around the cave. The floor in the cave is mostly covered by well sorted sand and rounded gravel in pebble to cobble size, in the deep area by well rounded gravel in cobble to boulder size, with the upslope floor growing steep. The height of the inflection point in the floor profile is also equivalent to those of the notches in and around the cave. In consequence, the levels of the paleo-shoreline along the Echizen Coast are more clarified by this study.
福井大学の論文