Improvements on the magnitude-geographic criterion of tsunami hazard

We suggest supplementing the MLH magnitude with the threshold ( M thr ) values of MPV , MSH , and MLH magnitudes (Russian scales), as well as M S and M W now in wide international use, for issuing tsunami alerts for hazards emanating from the main tsunamigenic zones of the Pacific Ocean. Relations are given to connect the MLH to these magnitudes. A comparative analysis applied to a catalog of large ( M ≥ 6) earthquakes in the North Pacific and to the associated tsunami catalog gave the probabilities of false alerts and unpredicted tsunamis as functions of the threshold magnitude value ( M thr ). A two-step decision rule is proposed to issue tsunami alerts due to the tsunamigenic zones situated close to the Far East coast of Russia.