足摺岬周辺の離水波食地形と完新世地殻変動
1988 年 43 巻 4 号 p. 231-240
詳細
1988 年 43 巻 4 号 p. 231-240
Around Cape Ashizuri, evidences for former sea levels are recognized as notch, wave cut bench and calcareous remains of organisms living in tidal zone. This paper aims to clalify coseismic crustal movement during Holocene based on geomorphological and biological sea-level indicators around Cape Ashizuri. Based on vertical distribution of former sea level indicators, four former sea levels are distinguished at Cape Ashizuri, i.e. I:4.7m, II:3.5m, III:2.0m, IV:unknown in height. These former sea levels are aged as I:around 4800 y.B.P., II:at least 2730 to 2430 y.B.P., III:around 1770 y.B.P., IV:unknown by means of radiocarbon dating. The earthquakes having caused these abrupt drops of former sea levels are named event 1 to event 4 in counter chronological order. Event 2 to event 4 occurred at 1770 to O y.B.P. , 2430 to 1770 y.B.P., 4800 to 2730 y.B.P. respectively. Judging from radiocarbon ages and distribution of amount of uplift, earthquakes (event 4 and event 3) in Ashizuri region could be correlated to earthquakes (event 6 and event 4) in Muroto region (Maemoku, 1988) respectively. These earthquakes are assumed not to be interplate, but to be intraplate ones.
