New Mexico Geological Society Annual Spring Meeting — Abstracts

The shear wave (ß) velocity structure was obtained for a great circle path across the Rio Grande Rift (San Augustin plains to Carrizozo, New Mexico) from the linear inversion of phase velocity data acquired from NTS explosion SERENA.

The model is comprised of twelve perfectly elastic, homogeneous, isotropic horizontal layers over an infinite halfspace. Initial model parameters, i.e. shear wave velocities, were based upon refraction studies in the region. Due to the limited bandwidth of the data, velocities below 22 km were not allowed to vary significantly during the inversion. Of the twelve initial velocities, only three distinct velocity regions were obtained. The final model consists of 2 km of sediment with ß=2.48 km/sec overlying a layer 20 km thick with an average ß=3.43 km/sec. The portion of the crust below 22 km was constrained to a shear wave velocity of 3.80 km/sec over a mantle with ß=4.40 km/sec.

The final model was compared to a surface wave study for the Albuquerque-Belen basin. The general trends of both final models are very similar. However, the pronounced velocity minimum seen at approximately 18 km in the Albuquerque-Belen basin is not apparent on the final model for the path between the San Augustin plains and Carrizozo.