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Two-dimensional elastic pseudo-spectral modeling of wide-aperture seismic array data with application to the Wichita Uplift-Anadarko Basin region of southwestern Oklahoma

CENTER FOR LITHOSPHERIC STUDIES THE UNIVERSITY OF TEXAS AT DALLAS, P.O. BOX 830688, RICHARDSON, TEXAS 75083-0688

Abstract

Full wave field modeling of wide-aperture data is performed with a pseudospectral implementation of the elastic wave equation. This approach naturally produces three-component stress and two-component particle displacement, velocity, and acceleration seismograms for compressional, shear, and Rayleigh waves. It also has distinct advantages in terms of computational requirements over finite-differencing when data from large-scale structures are to be modeled at high frequencies.

The algorithm is applied to iterative two-dimensional modeling of seismograms from a survey performed in 1985 by The University of Texas at El Paso and The University of Texas at Dallas across the Anadarko basin and the Wichita Mountains in southwestern Oklahoma. The results provide an independent look at details of near-surface structure and reflector configurations. Near-surface (<3 km deep) structure and scattering effects account for a large percentage (>70 per cent) of the energy in the observed seismograms.

The interpretation of the data is consistent with the results of previous studies of these data, but provides considerably more detail. Overall, the P-wave velocities in the Wichita Uplift are more typical of the middle crust than the upper crust (5.3 to 7.1 km/sec). At the surface, the uplift is either exposed as weathered outcrop (5.0 to 5.3 km/sec) or is overlain with sediments of up to 0.4 km in thickness, ranging in velocity from 2.7 to 3.4 km/sec, generally increasing with depth. The core of the uplift is relatively seismically transparent. A very clear, coherent reflection is observed from the Mountain View fault, which dips at 40° to the southwest, to at least 12 km depth. Velocities in the Anadarko Basin are typical of sedimentary basins; there is a general increase from 2.7 km/sec at the surface to 5.9 km/sec at 16 km depth, with discontinuous reflections at depths of 8, 10, 12, and 16 km.