Abstract

In conjunction with the 1979 COCORP Wichita Uplift survey, wide-angle reflection-refraction data were recorded on a fixed array. The object of the present study is to model and interpret these wide-angle data to add independent constraints on the deep structure of the Wichita Uplift. Three common-receiver profiles were extracted from the data; recording apertures were 3.2 to 23.4 km to the north of the array, 4.2 to 14.9 km to the east, and 4.2 to 12.6 km to the west. These profiles are modeled by iterative fitting of high-frequency synthetic seismograms computed by asymptotic ray theory.

The model derived contains low velocity (2.0 to 2.16 km/sec) surficial sediments that vary in thickness. These account for strong local travel-time variations of ±0.05 sec and for a small, but persistent “ghost” arrival that follows all the main branches with a delay of ≈0.2 sec. The basement granites, rhyolites, and gabbros are very near the surface throughout the study area; both granite and gabbro outcrops are seen. Basement P-wave velocities are therefore relatively high. Representative velocities are 4.7 km/sec at 0.8 km depth, 6.2 at 1.8, 6.4 at 2.8, and 6.5 at 4.0. Local velocities as high as 7.4 km/sec may be present. The basement is fairly transparent beneath the Wichita Uplift, with only a few local reflectors present. This is consistent with the COCORP results.

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