Application of two‐dimensional synthetic seismogram modeling to interpretation of wide‐angle seismic data from Wind River, Wyoming

Abstract

In conjunction with the 1977 COCORP Wind River project, wide‐angle reflection‐refraction data were recorded on a fixed array. The goals of the present study were to model these wide‐angle data to provide independent constraints on the Wind River structure. A common‐receiver profile extracted from these data forms a pseudo split spread with maximum offsets of 13.3 km toward the southwest and 19.1 km toward the northeast. The first 10 s of these data are modeled by iterative fitting of synthetic seismograms computed by asymptotic ray theory. The result is a two‐dimensional velocity model that extends from the center of the Wind River Mountains into the Wind River Basin and from the earth's surface to a depth of 25 km. The major features of the model are (1) surficial sediments that thicken toward the center of the Wind River Basin, (2) Precambrian basement that underlies the sediments and outcrops in the Wind River Mountains, (3) an intrabasement reflector at ∼5 km depth, (4) a low‐velocity region from ∼6 to 15 km depth, (5) a local, high‐reflectivity laminar zone (possibly an intrusive feature) at ∼15 km depth, (6) a second‐low velocity region from ∼17 to 23 km depth, and (7) a laminar transition zone between 23 and 25 km depth that separates the middle crust (average velocity ∼6 km/s) from the lower crust (average velocity ∼7 km/s). This study clearly reveals the major crustal structures. The most interesting result is tentative evidence that they may be secondary local intrusion of high velocity material as well as the primary horizontal thrusting in the Wind River uplift.