HR: 1340h
AN: H23A-1120    [Abstracts]
TI: Sled-Mounted Geophone Arrays for Near-Surface (0-4m) Seismic Profiling in Highly-attenuating Sedimentary Facies: Atchafalaya Basin Indian Bayou, Louisiana
AU: * Lorenzo, J M
EM: juan@geol.lsu.edu
AF: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803-4101 United States
AU: Saanumi, A A
EM: adeniyi@geol.lsu.edu
AF: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803-4101 United States
AU: Westbrook, C C
EM: cwestbrook@geol.lsu.edu
AF: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803-4101 United States
AU: Egnew, S F
EM: segnew@geol.lsu.edu
AF: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803-4101 United States
AU: Bentley, S J
EM: sjb@lsu.edu
AF: Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803-4101 United States
AB: Towed land-geophone seismic arrays have the potential to increase markedly the efficiency for collecting near-surface (0-100m) high-resolution seismic data, but viable cases are few and have been limited to a narrow range of near-surface sedimentary facies. During November 2003 through June 2004 we conducted extensive seismic tests with traditional geophones mounted on low-cost $\Pi$-shaped sleds. We targeted human habitation surfaces within the upper few meters of a crevasse splay complex in the Atchafalaya Basin study area, Indian Bayou Wildlife Management Area, Louisiana, U.S. For seismic-to-core correlation, sealed, continuous test cores were run through a multi-sensor to test for magnetic susceptibility, bulk sediment density and electrical resistivity. We compared 24-channel seismic data using a variety of seismic source-receiver combinations. Sources comprised a 12-gauge pipe-gun, a 0.22 caliber-powered piston gun, an accelerated weight drop, and a small claw hammer. Commercial blanks, 2g-black-powder, and primer-only shells were fired by the pipe gun. Receivers included 100-Hz vertical-, and 14-Hz-horizontal-component geophones. For comparison, both ground-planted and geophones mounted on wooden and iron sleds 0.3 and 1.2m long respectively. Geophones mounted on steel sleds produced data of adequate quality. Whereas traditional ground-planted geophones showed better data quality, time and cost efficiency make mounted phones more feasible for regional studies as traditional arrays are prohibitively expensive. Because of the high seismic attenuation, only horizontal-component geophones mounted on heavy (9-kg) steel sleds provided useful data, although the shallowest reflection observed in the shear wave data came from a boundary at ~ 19m depth, too far below the target depth of 4-5 m. Instead, we forward-modeled refraction traveltime data to derive the acoustic and SH velocity structure.
DE: 8194 Instruments and techniques
DE: 7294 Instruments and techniques
DE: 0900 EXPLORATION GEOPHYSICS
DE: 0935 Seismic methods (3025)
DE: 0994 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting