HR: 0800h
AN: S31A-0274    [Abstracts]
TI: Extending Ambient Noise Surface Wave Tomography to Continental Scales: Application Across the United States
AU: * Bensen, G D
EM: gbensen@colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado, Boulder, Campus Box 390, Boulder, CO 80309 United States
AU: Ritzwoller, M H
EM: ritzwoll@merckx.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado, Boulder, Campus Box 390, Boulder, CO 80309 United States
AU: Shapiro, N M
EM: nshapiro@merckx.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado, Boulder, Campus Box 390, Boulder, CO 80309 United States
AU: Levshin, A L
EM: levshin@phys-geophys.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics, University of Colorado, Boulder, Campus Box 390, Boulder, CO 80309 United States
AB: Ambient seismic noise contains a significant component of surface wave energy from which the Rayleigh wave Green function between pairs of stations can be extracted by cross-correlating long noise sequences. Surface wave tomography based on group velocities obtained on the estimated Green functions has been shown to produce high-resolution short-period (7-18 s) surface wave dispersion maps that image the principal crustal geological units in Southern California (Shapiro et al., Science, 307, 1615, 2005). In this study, we extend ambient noise tomography both in band-width (from 10 sec to 150 sec period) and geographical extent (across the entire United States). We have used data from about 125 stations (many of which constitute the Advanced National Seismic System (ANSS)) which together produce about 7500 inter-station paths across North America, providing much different data sampling than traditional teleseismic surface wave dispersion measurements. Cross-correlations are computed in five period bands between 10 and 150 seconds using at least one year of data. Temporal sub-setting provides uncertainty estimates on the group velocity measurements. The resulting group velocity maps have better resolution than those obtained by traditional methods based on earthquake waves, and demonstrate significant agreement with know geologic and tectonic features. They provide tighter constraints on crustal and upper mantle shear wave speeds and help to bridge the gap between global and regional scale 3-D models. Finally, the resulting cross-correlations are being used to constrain the source location, temporal variability,and frequency dependence of the ambient noise on which the tomographic method depends.
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005