Magnitude-Frequency Relation for Earthquakes in and near Japan.

Abstract

By means of the formulas determined by the present author previously, the magnitudes of 735 shallow earthquakes which took place in and near Japan during 1931-1950 were determined. The mean annual numbers of earthquakes having the magnitude M were found to be expressed by log N= -1.60+1.06 (8-M), for the area A, log N= -1.57+0.72 (8-M), for the area B, log N= -1.61+0.66 (8-M), for the area C, log N= -1.46+1.04 (8-M), for the area (A+B), log N= -1.33+1.01 (8-M), for the area (A+B+C), the class interval of M being taken as 0.1. It is interesting to note that while the first constant does not differ much from area to area, the second does so. The second constant for an area is nearly proportional to the total number of earthquakes which occurred in that area.