Abstract
　A zonal active region of shallow earthquakes along the longitudinal line of 139 E is deduced from the various catalogues of hypocenters including the newly compiled ones and the active faults. Earthquakes in this zone are more active at depths from 10 to 20 km between the Pacific Plate and volcanic region, and very-shallow earthquakes in the western part of Tochigi, eastern part of Yamanashi prefecture and near the Izu Peninsula are located in wider regions. Large earth-quakes in the active zone have the NW-SE or E-Wcompression, and can be distinguished from earthquakes of the N-S compression in the Shizuoka prefecture. The active zone is also coincident with the recent active crustal deformation, the positive short-wave length Bouguer anomaly and the northward migration of the moderate earthquakes after the 1930 North Izu Earthquake.
　Four seismic gaps are seen in this active zone, or (1) border region of Tochigi, Saitama and Gunma prefecture, (2) western part of Tokyo Metropolis. (3) northern part of Izu Peninsula and (4) region between the Izu Peninsula and Niijima Island. In these seismic gaps some historical or moderate earthquakes have been ocurred.

*東京大学地震研究所
Earthquake Research Institute, University of Tokyo