琵琶湖西岸における過去の崩壊に関連した湖底地形調査(序報)

Abstract

A large earthquake in 1662 (M=7.6, the epicenter: Takashima-machi, Shiga pref.) caus-ed a great deal of damage around Lake Biwa. Many land depressions along the westerncoast of Lake Biwa by the earthquake were recorded in historical manuscripts which repre-sent decrease in the agricultural field in many villages along the coast.Investigation of sedimentary structures near the coast with a Uniboom system showed theextraordinary structure brought about by coastal slope failures. We have found some faultsand trace of landslide in water in the surveyed area, but coastal land subsidences seem to becaused mostly by local compaction due to earthquake, as direct evidence of coastal landslideswas rare.Further investigation is needed to detect micro-topographic change and changes in resi-dential and agricultural areas along shore by the earthquake.