HR: 0800h
AN: S11B-1018    [Abstracts]
TI: M$_{s}$-m$_{b}$ Scaling for Earthquakes in Central Europe and Implications for Seismic Discrimination at Low Magnitudes
AU: Patton, H J
EM: patton@lanl.gov
AF: Los Alamos National Laboratory, P.O. Box 1663, MS F665, Los Alamos, NM 87545 United States
AU: * Schlittenhardt, J
EM: schlitte@sdac.hannover.bgr.de
AF: Federal Institute for Geosciences and Natural Resources (BGR), Stillweg 2, Hannover, 30655 Germany
AB: Teleseismic M$_{s}$-m$_{b}$ is generally regarded as one of the best seismic discriminants, and there is high interest in extending this classical discriminant to smaller magnitudes using regional data. Lg waves are well suited for monitoring small events since they are usually the largest signals on regional seismograms. Earthquake studies of Nuttli's m$_{b}$(Lg) have verified its transportability in continental areas of Europe, Asia, and North America, and a transportable M$_{s}$-m$_{b}$(Lg) relationship for earthquakes would be a significant advance for broad-area, nuclear test monitoring. The potential for M$_{s}$-m$_{b}$(Lg) discrimination might seem problematic, since in essence, it involves the comparison of two S-based measures, as oppose to the classical discriminant involving a P-based m$_{b}$. Nevertheless, several studies suggest that discrimination using m$_{b}$(Lg) might be better at low magnitudes due to differences in the scaling rates of m$_{b}$(Lg) and m$_{b}$(P) for underground explosions. In this study, we make use of frequency-wavenumber processing of Grafenberg Array data to extract Rayleigh waves for European earthquakes, and develop an M$_{s}$-m$_{b}$(Lg) relation extending to M$_{s}$ 2.5. This relation compares well with observations in other regions, including the western United States. We assess the discrimination potential with M$_{s}$-m$_{b}$ observations for explosions compiled from other studies, including the m$_{b}$(Pn) study of Bonner and co-workers. Earthquake relations for m$_{b}$(Lg) and m$_{b}$(Pn) scale similarly and practically overlie for 2.5 $<$ M$_{s}$ $<$ 5.5. On the other hand, explosion relations scale differently, where event populations remain parallel for m$_{b}$(Lg), but merge at small magnitudes for m$_{b}$(Pn). At the smallest magnitudes in this study, populations are separated by $\sim$0.5 magnitude units for both m$_{b}$(Lg) and m$_{b}$(Pn).
DE: 7219 Nuclear explosion seismology
DE: 7255 Surface waves and free oscillations
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting