Lithospheric Structure of the Arabian Shield From the Joint Inversion of Receiver Function and Surface-Wave Dispersion Observations
Technical rept. 28 Sep 1998-27 Sep 2000
SAINT LOUIS UNIV MO DEPT OF EARTH AND ATMOSPHERIC SCIENCES
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We estimate lithospheric velocity structure for the Arabian shield by modeling receiver functions and Love and Rayleigh group velocities from event recorded by the 1995-1997 Saudi Arabian Portable Broadband Deployment. Receiver functions are primarily sensitive to shear-wave velocity contrast and vertical travel times and surface-wave dispersion measurements are sensitive to vertical shear-wave velocity averages, so that their combination bridge resolution gaps associated with each individual data set. We incorporate depth-dependent smoothness constraints on the resulting velocity models utilizing a jumping inversion technique. Additional constraints for the upper mantle are placed during inversion to complement those provided in our data set. Our results show a 32-36 km thick crust consisting of a 10-12km thick upper crust containing a rapid velocity increase, a rather constant velocity, a rather constant velocity lower crust of 3.84-O.04 kms overlayed by a significant velocity gradient above 16-22 km depth. The upper mantle material is shown to have shear velocities ranging from 4.3 to 4.6kms and the crust-to-mantle transition is imaged as a gradational transition zone 4-12 km thick rather than a sharp discontinuity. Evidence for lateral variations in both crust and upper mantle is observed at some stations as well.