Wave-field tau-p analysis for 2-D velocity models: Application to western North American lithosphere

Abstract

The international Deep Probe refraction experiment is a continental-scale study of the crust and upper mantle in western North America to determine well-constrained mantle velocity-depth structures for the stable Archean Hearne and Wyoming provinces and the tectonically modified Proterozoic lithosphere of the southern Rocky Mountains and Colorado Plateau. An initial 2-D velocity interpretation for Deep Probe has been accomplished by the application of the downward-continued wave-field τ-p transform method. This approach involves two linear transforms for each shot gather from the experiment: a τ-p transform (or slant stack) of the input data followed by a downward continuation to z-p space using an appropriate velocity function. The determination of this velocity function is an iterative process which converges when the downward-continued wave field images a velocity function which is the same as that used to create it. The resulting 1-D velocity function, v(z), from each gather is converted to a 2-D function, v(x, z) using ray theory. Eleven profiles along the Deep Probe corridor have been analysed. The resulting functions have been combined, gridded and contoured to produce a velocity structure section for the project, which provides an initial model for the application of more advanced interpretation procedures. As a result, the lithospheric structures of three major tectonic provinces have been identified in an efficient and effective manner that did not require 'picking' of travel times. Copyright 1999 by the American Geophysical Union.