HR: 0800h
AN: S51E-1051    [Abstracts]
TI: Crust and Upper Mantle Shear-Velocity Structure of Eastern North America From the Joint Inversion of Receiver Function and Surface-Wave Dispersion
AU: * Fnais, M S
EM: m_fnais@yahoo.com
AF: King Saud University, Kingdom of Saudi Arabia P.O.BOX 2455, Riyadh, 11451 Saudi Arabia
AU: Herrmann, R B
EM: rbh@eas.slu.edu
AF: Department of Earth and Sciences, Saint Louis University, 329 Macelwane Hall 3507 Laclede Ave, Saint Louis, MO 63103 United States
AU: Zhu, L
EM: lupei@eas.slu.edu
AF: Department of Earth and Sciences, Saint Louis University, 329 Macelwane Hall 3507 Laclede Ave, Saint Louis, MO 63103 United States
AB: The crustal structure of the Eastern North America is estimated at available broadband seismic stations through a joint inversion of teleseismic P-wave receiver functions and surface-wave dispersion curves. The joint inversion techniques takes advantage of the average velocity information present in the surface-wave dispersion curves and the differential velocity information contained in the receiver functions. Starting with an initial constant velocity parameterization with 2-km thick layers in the upper 50 km overlying and AK135 upper mantle, the joint inversion, with a slight smoothing constraint, provides a model that is compatible with observations and yet has no pre-conceptions about the sharpness of the Moho. Moho depth is estimated as the depth at which the S-wave velocity passes through the 4 km/s threshold. A complementary approach focuses on determining the crustal thickness (Moho depth) by assuming an average crustal velocity and using the differential travel time between the direct arrival P-phase and the P-to-S conversion at the Moho discontinuity. This crustal thickness is strongly sensitive to the Vp/Vs ratio, but not very sensitive to the average crustal P velocity used. The results of this research are maps of crustal thickness and Moho sharpness for portions of eastern North America. Not all seismograph sites were suitable for this study. Stations located on thick low velocity sediments, e.g., Mississippi Embayment and Williston Basin, have receiver functions that are dominated by the reverberations in the upper kilometer. We expect this to be a problem for many USArray Transportable Array sites in the U.S.
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: Fall Meeting 2005