The crustal and upper mantle shear velocity structure of Eastern North America from the joint inversion of receiver function and surface-wave dispersion.

摘要

The crustal structure of the Eastern North America is estimated at all available seismic stations by using receiver function and surface-wave dispersion curves. A joint inversion technique is also used which takes advantage of average velocity information present in the surface-wave dispersion curves and differential velocity information contained in the receiver functions.; Since the receiver function itself is sensitive to the absolute velocity contrast, it can be used to estimate the crustal thickness (Moho depth) if average crustal velocities are assumed. Crustal thicknesses at each stations are estimated from the differential travel time (delay time) between the direct arrival P phase and the P-to-S conversion at the Moho discontinuity. The estimation of the crustal thickness is strongly sensitive to the VP/V S ratio, but not very sensitive to the average crustal P velocity.; Since the inversion of a receiver function is non-unique, surface-wave dispersion curves are used to add constraints on the inverted model through the use of a joint inversion technique to result in estimates of the crustal and upper mantle shear-velocity structure. At some stations the inverted model cannot be believed because of the strong effect of a thick shallow sediment layer masks the crustal information in the receiver function. The receiver function at stations MPH and FA20--FA28 can not be used for this method since the converted P-to-S phase can not be seen. The joint inversion provides shear-velocity models for the crust and upper mantle at other sites in the Eastern North America.