Further studies on seismic discrimination

Abstract

Further data on the shape of the M_s: m_b(6.5 ≧ m_b ≧ 4.0) curve for shallow-focus (D < 50 km) earthquakes are given along with theoretical explanations of the observed relationships. The frequency and probable cause of “anomalous” earthquakes is discussed. Capability of simple identification criteria (depth ≧ 50 km, detected Rayleigh waves of adequate amplitude, and/or location more then 25 km at sea), based on use of only a fraction of presently available data, is demonstrated. The magnitude of the mixed event (mixed surface waves of earthquakes) problem as it effects identification as well as procedures for circumventing the problem are demonstrated. Finally, recommendations are made for solving some other residual discrimination problems.