The Multi-Factor Model of Magnitude Residuals and the Problem of the Precise Determination of Magnitude.

Abstract : Station corrections for hundreds of stations and seismic waves dynamic data in many regions were jointly analyzed to study the statistical structure of seismic magnitude deviation. The multi-factor model of station residuals is proposed. It was found that total deviation of magnitudes (0.4 magn. units for EQs and 0.34 for UNEs) is formed by a set of components: (1) Site effects component S1 is equal to 0.10. (2) Area of observation component S2 is equal to 0.14. (3) The influence of the earthquake (EQ) zone is described by the component S3 which is also equal to 0.14. (4) The path effect component S4 is equal to 0.19. (5) The random component S5 is influenced by a variety of factors which are unknown. This component varies from 0.28 for EQs and 0.18 for UNEs. The real accuracy of magnitude depends not only on the number of stations used, but mostly on different areas and types of paths. Based on dispersion analysis of magnitude, a technique for realistic error estimates is proposed. The efficiency of station corrections is discussed. Our observations show, that even in cases when all factors are corrected, the lower limit of magnitude error is 0.07.