Premium
Empirical determination of depth‐distance corrections for m b and M w from global seismograph network stations
Author(s) -
Nolet Guust,
Krueger Steve,
Clouser Robert M.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl01094
Subject(s) - amplitude , magnitude (astronomy) , seismometer , moment magnitude scale , physics , geodesy , seismic moment , moment (physics) , scalar (mathematics) , logarithm , geometry , optics , geology , mathematics , seismology , astrophysics , mathematical analysis , fault (geology) , classical mechanics , scaling
Using P wave amplitudes from 52 deep earthquakes, recorded by the Global Seismograph Network (GSN) between 1991 and 1996, we empirically determined depth‐distance corrections for body wave magnitude m b and moment magnitude M w . After correcting vertical, broadband records from stations of the GSN for instrument response and source radiation factors, P wave amplitudes from velocity records were read for the case of m b and the surface area under the displacement pulse of the P wave for M w . Amplitudes were then normalized to a scalar moment M 0 =10 18 Nm, or m b =5.7, M w =5.9. Using the generic logarithmic relationship for each magnitude, correction factors Q (Δ, h ) were determined. A total of 973 observed values of Q in the plane of distance Δ vs. depth h were smoothed by local averaging, as well as fitted by a parameterized smooth surface. These empirical Q (Δ, h) surfaces differ in important detail from those historically established by Gutenberg and Richter, and markedly from the theoretical curves predicted by Veith and Clawson (1971). We present a first empirical correction factor for the determination of M w from P wave displacements.