Abstract
The travel times of P waves to Japan from the underground nuclear explosion of November 6, 1971, at Amchitka Island, the Aleutian Islands, deviate systematically with region in comparison with the travel times by CARDER et al. (1966). Arrival times at stations on the Pacific coastal region from Hokkaido to the northern Kanto area, the northern part of west Japan, and at islands near Japan (Izu Is., Ryukyu Is. and islands in the Sea of Japan) are somewhat earlier than the Carder et al. times. On the other hand, at stations in the southern Kanto, southern Chubu, central and southern Kinki, Shikoku and Kyushu areas, the arrival times are later as a whole.
The body wave magnitude MB, estimated from the data in the Japan Meteorological Agency network is larger by about 0.7 than that reported by USNOAA. It is noticed that the discrepancy between them is probably caused by the difference of the frequency responses of seismographs used for the estimation.
