Analysis of multichannel seismic reflection profiles gathered by the Consortium for Continental Reflection Profiling (COCORP) constrains the geometry and material properties of a proposed magma body located within the Rio Grande rift. A new spectral ratio method is used to find the reflectivities of the proposed midcrustal intrusion; large and spatially variable reflectivities support the interpretation of the reflector as an intrusive molten magma complex. Modeling of the reflectivity suggests that in one location the intrusion took the form of several thin (30 to 40 m thick) layers. Seismic wave attenuation within the rift's midcrust in low.