This three-year (2009-12) collaborative project integrates arch-scale upper crustal geometries from surface exposures and petroleum industry subsurface data (Eric Erslev, University of Wyoming; Christine Siddoway, Colorado College) with the results of a hybrid seismic experiment consisting of both passive and active components (BASE). The passive component of the seismic experiment consisted of a 1.25 year (2009-10) deployment of 38 broadband seismometers that densified the EarthScope transportable array (Megan Anderson, Colorado College), a 6.5 month deployment of 158 short period seismometers (Anne Sheehan, University of Colorado), and a 9 day deployment of 850 high frequency "Texan" seismometers (Kate Miller, Texas A&M University; Sheehan). Passive instruments were arrayed in a grid consisting of three SW-NE lines and two NW-SE lines. The active component consisted of 24 shots (summer 2010) recorded by the above broadband and short period instruments plus 1850 "Texan" seismometers deployed for 5 days (Steve Harder, University of Texas, El Paso; Miller). The 1850 Texans were deployed on the middle and west transect only. Joint inversion of active and passive results defines crustal and upper mantle velocities and interface structures within the Bighorn Arch. These new seismic results are integrated within a GIS-based, 3D geospatial framework including data from exposures, geologic maps and industry subsurface data for the study area. Kinematic information from fracture transects (Erslev, Siddoway) and gravity modeling (Miller) is used to guide 3D, lithosphere-scale structural restorations to test the compatibility of different components in our 3D geometric model.
left: Design of the BASE experiment on a shaded relief digital elevation model of the northern Rocky Mountains (BHM: Bighorn Mountains). Blue lines represent the 5 passive / active source transects, with active source shots marked by small red stars. Broadband seismic stations (green squares) infill the USArray grid (TA broadband stations, black triangles). Large red stars are source areas for mine blasts. Circles are epicenters for regional seismicity, 1973 to 2008.