抄録
It has been generally known that earthquakes take place at any depth in the crust as far as about 500km. below the surface. For the investigation of near earthquakes, a standard table of travel time of seismic waves transmitted from the origin of variable depths is required to be made by the recent materials obtained in the seismometrical observation. For this purpose, the time-distance curve of the great earthquake occurred in North Idu district on Nov. 26, 1930 is adopted and the values of seismic wave velocity calculated by Mr. Honda are used in this paper. Thus, several tables of the travel time concerning the depth of focus and the epicentral distance are obtained. They are considered to be applicable for various branches of our practical seismology. Further, we have also calculated a table of the correction due to the depth of focus which must be applied on the travel time at a large epicentral distance in the case of distant earthquakes. As for further investigations of seismic wave propagation based upon the present tables, we shall write in the next report.
