Abstract
Some triangulation stations located in the northern part of the Izu Peninsula, Japan, were moved to SSE direction by more than two meters during the 1923 Kanto earthquake. These movements were generated by faulting along the Sagami-Bay fault and the Nishi-Sagami-Bay fault. Succeeding to this event, the 1930 Kita-Izu earthquake occurred. Around the occurrence of the earthquake, anomalous crustal movements were associated during pre- and post-seismic period. Parameters of a creep dislocation model for the observed anomalous crustal movements during the period 1931-1933/1934 are given as follows;strike of fault φ=N7°E, length of fault L=20 km, width of fault W=30 km, dip angle δ=45°, dept of upper side of fault plane H1=4.2km, depth of lower side of fault plane H2=25.5km, dip slip Ud=43cm, left-lateral strike slip Us =43cm. A similar creep dislocation might precede the occurrnce of the 1930 Kita-Izu earth-quake, and additional strain given by a creep dislocation triggered the 1930 Ito earthquake swarm. Migration of the seismic activities from 1923 to 1930's may be mediated by creep dislocation at the depth of the thrust along the East-off-Izu tectonic line.
