HR: 0800h
AN: S11B-0565    [Abstracts]
TI: Testing Models of North American Seismic Velocity Structure With Traveltimes From Well-Validated Sources
AU: * Menke, W
EM: menke@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Richards, P G
EM: richards@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Kim, W
EM: wykim@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Waldhauser, F
EM: felixw@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Schaff, D
EM: dschaff@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AB: Surface wave tomography has provided 3D models of the seismic structure of the continents, down to depths of several hundred kilometers (e.g. Van der Lee and Nolet, 1997; Nettles and Dziewonski, 2007). On the one hand, these models are limited by their low horizontal resolution (hundreds of kilometers) and by providing estimates of shear velocity but not compressional velocity. On the other hand, they have the virtue of having a uniform spatial resolution and are based on data (surface wave dispersion) that are only very weakly dependent on the location and origin time of the underlying earthquake sources. This near independence is relevant, for instance, in developing velocity models and/or traveltime models for earthquake location, because the problems associated with circularity-of-results (e.g. the same earthquakes both determining the model and being located by it) are avoided. We discuss the conceptual and practical problems associated with using surface wave results to calculate continental-scale traveltimes and to locate earthquakes. We build such a model of North America and test it against continental-scale traveltimes from five PNE's and the Early Rise series of chemical explosions. Traveltime residuals are reduced by 50 percent compared to the predictions of a radially-stratified model, but some regionally coherent traveltime residuals remain, indicating that the 3D model derived from surface waves is capturing some, but not all, of the actual variability beneath the continents.
DE: 7218 Lithosphere (1236)
DE: 7255 Surface waves and free oscillations
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting