1980年伊豆半島東方沖地震による津波

Very small tsunami was generated by the main shock (M=6.7) in an earthquake swarm off Ito, the east side of Izu Peninsula, on June 29, 1980. The maximum double amplitude of 56 cm for a period of 3.5 min was observed at Okada, Izu-Oshima Island, while those at other tide stations in Sagami Bay were about 10 cm. Tsunami magnitude of the Imamura-Iida scale is m= -1.5. The source area of tsunami inferred from the inverse refraction diagrams agrees well with the earthquake swarm. The source area extends 17 km in the N20°W direction. Judging from the initial motion of tsunami on the records, an uplift of several centimeters may have occurred at the sea-bottom of the source area. The present tsunami had both a small wave-height and source dimension, just like other Izu tsunamis in 1974 and 1978