Regional Amplitude-Distance Relations, Discrimination and Detection

This paper begins with a review of the literature on propagation of Pn, Pg, Sn, Lg, and Rg and continues with the history of discrimination at regional distances up to 1978. New work performed especially for this report is discussed next distance amplitude relations for Pn, Pg, Lg and for the maximum amplitude observed before and after Sn are presented for earthquakes and explosions in both the Eastern United States EUS and the Western United States WUS. By means of references to the work reviewed in the literature review, these results are then placed in context, and decay rates are attached to the amplitude-distance curves so that they may be used in magnitude estimation. Then these distance-amplitude relations are used to define event magnitudes log amplitude at 1000 km for each phase and the discrimination capability of a compressional and shear magnitude is investigated in a fashion analogous to the conventional Msmb. Finally, several topics are discussed with the aid of spectra of explosions and earthquakes. Among these are detection threshold, optimum filter for detection of regional events, and difference in source spectra for earthquakes and explosions.