Attenuation function of displacement amplitude for magnitude calculation

Abstract

We estimated an attenuation function of displacement amplitude based on moment magnitude. The function enable us to calculate conventional magnitude that would agree with moment magnitude on the average in all depth ranges. Magnitude calculated with the function is smaller than that calculated with M. Katsumata's formula by about 0.3 for deep-focus earthquakes. The function is applicable to data when the hypocentral distance is from about 30 to 2000 kilometers. The function was estimated based on data from the Japan Meteorological Agency (JMA) between January 1977 and February 1994. Some corrections are provided to apply the function to data from the current JMA seismological network developed in 1994.