Abstract
During a seismic activity in Izu Islands from June 26 to August 31, 2000, there was a moderate earthquake MJMA 6.4 followed by a small tsunami on July 1. The tsunami was observed at tide stations in Kouzu-shima and Miyake-jima Islands. Assuming a vertical displacement due to a static fault with the seismic focal mechanism and moment, we numerically computed the tsunami to explain the observed waveforms. The location and the size were varied in a possible finite range and the best values were estimated on the basis of correlation coefficient of amplitude between model and observation. From the maximum value of 0.65 it is concluded that the fault was located at sea in the east of Kouzu-shima Island with length of 11km and depth of 1km. The central position at 34.222°N and 139.235°E corresponds to a north margin of the earthquake swarm. The fault length is comparable with one of the swarm area. The subsidence area, formed at southeast part of the fault, covers the most of the swarm area. This subsidence does not conflict with a magma motion toward the northwest direction.
