Reanalysis of the COCORP Utah Line 1 deep seismic reflection profile: Toward an improved understanding of the Sevier Desert detachment question

Abstract

The Sevier Desert detachment (or reflection, SDR), which underlies the Sevier Desert basin along the eastern margin of the USA Basin and Range, is commonly cited as a type example of a low-angle normal fault (LANF) in continental crust. We present the results of reanalyzing the SDR on the COCORP (Consortium for Continental Reflection Profiling) deep seismic profile crossing the Sevier Desert basin (Utah Line 1). We employ a strategy of showing how shallow crustal velocity models, derived from first-break analysis of the shot records, may be used to reduce the effect of lateral velocity variations on imaging the SDR. Our results imply that the irregularities and discontinuities along the SDR are likely caused by overlying lateral velocity variations. The reprocessed versions of the section reveal a smoother, simpler, and more continuous SDR, lacking most of the apparent large offsets and structural variations on the currently available version of the profile. Seismic attribute and structural analyses of the reflection indicate significant variations along the profile, which are likely related in part to the field acquisition, but may also suggest lateral variations in the physical origin of the SDR. Such lateral variations may be consistent with previous studies that challenge the LANF interpretation of the SDR on the basis of attributing different origins to different parts of the reflector; however, a smoother and more continuous SDR points to a tectonically uniform origin and is thus interpreted to be more consistent with a LANF explanation.