抄録
On November, 29, 1974, a 465.5kg explosion was made by Geological Survey of Japan for measuring the secular variation of seismic wave velocity in the Kanto district. This explosion was used by the present author for investigating the seismic wave attenuation and the crustal structure beneath the Izu Peninsula. Seven temporary stations were installed by the author for these purposes in the Izu Peninsula and to the west of the Suruga Bay. The data at five stations among seven and at other five stations, operated by others at that time, were obtained.
The results are as follows; (1) The velocity amplitude decay is represented as Δ-3 in the frequency range from 5Hz to 10Hz, where Δ is the epicentral distance. (2) The travel time delay at the stations to the west of the Suruga Bay are as large as 1.0 to 1.5sec. compared to those estimated from the travel times in the Izu Penisula. These results show that the attenuation factor in the crust beneath the Izu Peninsula is larger than those in the other regions and the crustal structure beneath the Suruga Bay and the Izu Peninsula is complicated.