Distance dependence of Ms and calibrating function for 20 second Rayleigh waves

Abstract

Abstract The study of 5514 Ms readings reported to the International Seismological Center and U.S. Geological Survey revealed that Ms values as obtained by the Moscow-Prague formula are significantly distance dependent. Average relative errors of over 0.5 magnitude units are made when using amplitude readings from very near and very distant stations. The new calibrating function for 20 sec Rayleigh waves is proposed in which the amplitudes decrease as distance+1.094, which agrees with results of theoretical studies.