Shallow velocity structure of the Rio Grande Rift north of Socorro, New Mexico: A reinterpretation

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Abstract
Shallow (upper 1.2 km) compressional wave velocity models from line 2A of the Socorro, New Mexico, Consortium for Continental Reflection Profiling (COCORP) survey of the Rio Grande rift supplement a previous refraction study of Socorro COCORP lines 1 and 1A. First‐arrival refraction analysis and slant stacks of the refraction profiles (derived from the reflection data) are used to determine velocity models of Socorro COCORP line 2A. Exposure of Paleozoic and Mesozoic sedimentary formations in the vicinity of Socorro line 2A allow direct correlation of a unit's velocity to its geological era. Weathered Mesozoic and Paleozoic formations within the rift are inferred to have significantly lower velocities than previously believed. Reinterpretation of the Rio Grande rift structure in the survey area results in a model that is consistent with available gravity data and provenance studies. The 13 km of Cenozoic spreading determined from the model is at least 5 km higher than that found 80 km to the north. There is evidence of minor Paleozoic deformation or nondeposition.