44 Relationships between magnitude scales

Abstract

This chapter describes relationships between magnitude scales. Magnitude scales were introduced by Richter and were designed for earthquakes in southern California recorded by the network of Wood-Anderson seismometers. This scale was then extended in many ways to apply to the data produced in various observational environments. New magnitude scales constructed, provide equal magnitude values to the same earthquakes or the earthquakes, which radiated the equal amount of energy. The chapter essentially considers earthquakes of all depths. The empirically obtained curves for the relationship between two magnitude scales represent earthquakes with average source characteristics. Significant deviation of a data point from the curve can usually be attributed to anomalous source characteristics of the event such as a nuclear explosion or a tsunami earthquake. Various magnitude scales considered include—namely, (1) local magnitude , (2) surface-wave magnitude, (3) body-wave magnitude, (4) moment magnitude, and (5) Kawasumi's magnitude.