The Frequency of Very Large Earthquakes

Observational data relating surface wave magnitude M s to seismic moment M 0 are used to convert a well-known frequency- M s plot into a frequency- M 0 relationship, which turns out to be remarkably linear. There is no evidence of an upper bound to M 0 , on the basis of presently available evidence. The possibility exists that extremely large earthquakes ( M 0 = 10 31 dyne-centimeters or greater) may occur from time to time.