Abstract

The U.S. Geological Survey conducted seismic refraction-reflection studies in the Datil-Mogollon volcanic field, southwestern New Mexico and southeastern Arizona, during 1976–1980. Explosions originating in the White Sands Missile Range (New Mexico), Tyrone (New Mexico), Morenci (Arizona), and Miami (Arizona) were used as energy sources. The observations can be satisfied with a simple three-layer crustal model, although there is evidence for complexities in both of the lower layers. The surface layer varies between about 2 and 4 km thick and is composed of volcanic rocks that have an average P-wave velocity of 4.0 km/s. The basement rocks are about 21 km thick and have a P-wave velocity of 6.0 km/s. There is evidence for a distinct lower crust beneath the volcanic field. This layer, about 9 km thick, has a P-wave velocity of about 6.5 km/s. The Pn velocity is 8.0 km/s, the total crustal thickness is about 33 km, and the average P-wave velocity in the entire crust is about 6.1 km/s. There is no evidence for substantial dip along any of the refractors beneath the profile.

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