Earthquake Magnitude and Surface Fault Formation

Abstract

Observational relation of fault length to earthquake magnitude is tentatively illustrated by concept of the geometrical relation between earthquake focal region and earth's crust as is schematically shown in the inset of Fig. 2. Fault lengths thus interpreted seem to be in good accordance with concept of the voluminal storage of the earthquake energy. Proposed model can also explain the observational fact that percentage of the number of earthquakes of a given magnitude M accompanied by fault, to the total number of the earthquakes of that magnitude increases from 60% for 7.0<M<7.4 to 100% for 7.4<M.