Item

Abstract

The determination of source parameters requires corrections for propagation and site effects. The source parameter of interest for this study is the radiated seismic energy, which we use in turn to compile a global energy magnitude Me catalog. The energy estimated for P waves recorded at distances between 20° and 98° is corrected for propagation effects using the numerical Green’s function for the AK135Q model, in which the correction is performed in the spectral domain over the frequency range 0.012–1 Hz. To quantify the impact of site effects on Me, we perform a mixed-effects regression to isolate repeated station effects from event and propagation contributions to the overall magnitude variability. We find that the standard deviation of the interstation residuals is 0.19, whereas the standard deviation of the path-to-path residuals is 0.24. To discuss the spatial variability of the station-specific magnitude residuals, we analyze the results obtained for permanent and temporary networks installed in the conterminous United States. The high density of stations considered (4502 stations from 97 networks) allows us to compare a map of the station corrections with the physiographic classification of the United States. We find a good agreement, with positive magnitude corrections for stations installed in the Atlantic Plain and in the Interior Plains divisions; negative corrections characterize installations in the Rocky Mountains system, in the Interior Highlands, in the ranges of the Pacific Mountains division and in the Appalachian Highlands. Moreover, the alternation of positive and negative magnitude corrections corresponds well with the province and section subdivisions.