HR: 0830h
AN: S11C-0316    [PDF]
TI: Imaging the Cheyenne suture beneath the Laramie Array in southeast Wyoming
AU: * Yuan, H
EM: yuan@uwyo.edu
AU: Dueker, K
EM: dueker@uwyo.edu
AB: The objective of the PASSCAL Laramie Array deployment was to resolve the crust and sub-crustal lithosphere velocity and discontinuity structure beneath the Cheyenne belt, which demarcates the suture between the Archean Wyoming province and the Proterozoic Colorado province. From Sept. 2000 to June 2001, thirty-one broadband sites at a 2 km station spacing were deployed along a N20­aW transect in the Laramie Basin. Receiver function (RF) transect from the PASSCAL CD-ROM experiment 100 km to the west of the Laramie Array shows substantial dipping crust and sub-crustal velocity discontinuities across the Cheyenne belt. Assuming these structures are related to the 1.78-1.75 Ga Cheyenne suturing event, significant seismic anisotropy within the suture zone is expected to produce systematic variations in the receiver functions. Joint radial and tangential receiver functions analysis is being used to constrain the difficult trade-off between interfaces dip and anisotropic velocity heterogeneity. Our preliminary results show a clear image of the Moho that appears not to require velocity anisotropy and a north dipping mid-crustal interface beneath the entire array. This north-dipping interface is opposite to the generally accepted south-directed polarity of the Cheyenne belt. A strong correlation exists between this mid-crustal interface and large lateral variations in the upper crustal P-wave velocities derived from the teleseismic travel-time inversion. Further analysis to constrain potential crustal velocity anisotropy will be presented.
DE: 1734 Seismology
DE: 6982 Tomography and imaging
DE: 7200 SEISMOLOGY
DE: 7205 Continental crust (1242)
DE: 8125 Evolution of the Earth
SC: Seismology [S]
MN: 2003 Fall Meeting