EARTHQUAKE SIZE AS A FUNCTION OF FAULT SLIP RATE

Estimates of the potential size of earthquakes on mapped active faults are generally based on regressions of earthquake magnitude (M(w)) ver sus length (L) of fault rupture for historical earthquakes. The fault slip rate (S) has been ignored in formal prediction equations, but mor e accurate predictions of future earthquake magnitudes on mapped fault s may be obtained when it is included. A least-squares regression for a data set of 43 earthquakes occurring on faults for which slip rates are reported shows M(w) = 5.12 + 1.16 log L - 0.20 log S, where L is i n units of Km and S is in units of mm/yr. The result indicates that th e largest earthquakes will occur on the slowest slipping faults if the rupture length is held constant.