HR: 0830h
AN: S41B-01    [Abstracts]
TI: Broadband surface wave dispersion measurements across North America from ambient seismic noise
AU: * Bensen, G D
EM: gbensen@cires.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics University of Colorado Campus Box 390, Boulder, CO 80309-0390 United States
AU: Shapiro, N M
EM: nshapiro@fignon.colorado.edu
AF: Center for Imaging the Earth's Interior, Department of Physics University of Colorado Campus Box 390, Boulder, CO 80309-0390 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 Campus Box 390, Boulder, CO 80309-0390 United States
AU: Campillo, M
EM: michel.campillo@obs.ujf-grenoble.fr
AF: LGIT, Universite Joseph Fourier, Grenoble, France,
AU: Stehly, L
EM: lstehly@obs.ujf-grenoble.fr
AF: LGIT, Universite Joseph Fourier, Grenoble, France,
AB: Ambient seismic noise contains a significant component of Rayleigh wave energy that appears to be excited by oceanic microseisms and atmospheric forcing. These signals constitute a wavefield in which the phase is randomized by a multiplicity of sources and by scattering. Cross- correlations of the ambient wavefield between pairs of receivers can be used to extract the Rayleigh wave part of Green's function and, therefore, provide a new source of surface wave information that is particularly useful in the context of arrays of broadband seismometers such as PASSCAL experiments, the emerging USArray, or other national deployments. The method produces numerous inter-station measurements that are not sampled by traditional observational methods based on earthquake waves. The method to extract surface wave dispersion measurements from ambient noise was first applied systematically to records from USArray Transportable Array stations in California. These observations were used to construct high-resolution short-period (7-18 s) surface wave dispersion maps and to image the principal crustal geological units. In addition, it has been previously shown that reliable dispersion meausurements can be obtained at intermediate to long periods (20 - 100 sec). In particular, cross-correlations of several months of ambient seismic noise observed at several station-pairs across North America result in coherent broadband waveforms with dispersion characteristics similar to Rayleigh-wave tomography maps constructed using earthquakes waves. We extend this work by computing cross-correlations and obtaining intermediate and long period surface wave group velocity measurements for paths connecting about one hundred permanent broadband stations in North America many of which constitute the Advanced National Seismic System (ANSS). We discuss the promise and limitations of the method to improve information about the crust and upper mantle across North America.
DE: 7200 SEISMOLOGY
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: 2005 Joint Assembly