HR: 09:00h
AN: NS21A-03 INVITED     [Abstracts]
TI: High-Resolution Seismic Investigation of a Surface Collapse Feature at Weeks Island Salt Dome, Louisiana
AU: * Miller, R D
EM: rmiller@kgs.ku.edu
AF: Kansas Geological Survey, 1930 Constant Avenue, University of Kansas, Lawrence, KS 66047-3726 United States
AU: Xia, J
EM: jxia@kgs.ku.edu
AF: Kansas Geological Survey, 1930 Constant Avenue, University of Kansas, Lawrence, KS 66047-3726 United States
AU: Harding, R S
EM: richard.s.harding@bhpbilliton.com
AF: BHP Petroleum (Americas) Inc., 11702 Monica Lane, Houston, TX 77024 United States
AU: Steeples, D W
EM: don@ku.edu
AF: Department of Geology, 1475 Jayhawk Blvd, Rm 120, 120 Lindley Hall, Lawrence, KS 66045 United States
AB: Seismic imaging techniques delineated the subsurface expression of an active sinkhole above a former salt mine at Weeks Island, Louisiana, which was used at the time by the U.S. Department of Energy's Strategic Petroleum Reserve. (The Weeks Island salt dome is no longer part of the Reserve.) The sinkhole, which at the time of the survey was approximately 12 m wide and 11 m deep, is directly over the edge of the upper storage chamber and approximately 60 m above the top of the salt dome. Surface seismic reflections imaged a dramatic bowl-shaped depression in a 28-m-deep reflector spatially consistent with the sinkhole. Two reflections (28 m and 60 m) on multichannel VSP data represent the only velocity and/or density contrasts detected above the top of the salt dome. The 28-m reflector identified on both VSP and surface seismic reflection data is at a depth consistent with the piezometric surface. Considering the high measured permeability and relative geometric severity of the reflection geometry, it is questionable whether this drape in the 28-m reflection is consistent with the water table. Localized velocity variations could account for some of the apparent geometry. The 60-m salt reflection, evident on VSP, can be interpreted on selected processed surface seismic shot gathers, but is difficult to confidently and consistently identify on stacked sections. The sinkhole lies along a northeast-trending acoustic lineament, possibly related to or associated with salt dissolution. The acoustic expression of the sinkhole suggests a localized, predominantly vertical feature. No evidence was discovered to confidently ascertain the mechanism responsible for exposing the salt to unsaturated meteoric water.
DE: 0902 Computational methods, seismic
DE: 0935 Seismic methods (3025)
DE: 5470 Surface materials and properties
DE: 7223 Seismic hazard assessment and prediction
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly