Crosshole seismic tomography: working solutions to issues in real data travel time inversion
File(s)
Published version
Author(s)
Rao, Y
Wang, YH
Type
Journal Article
Abstract
In travel time inversion of crosshole seismic tomography, when dealing with real data, the following three issues need to be addressed: how to suppress the effect of data errors, how to balance the data contribution and reference model, and how to properly set the geological constraints (well logs) in an inversion. Signal-to-noise ratios of travel time data picked from real crosshole seismic surveys likely depend on the vertical offset between a source and a receiver, since the overall attenuation will typically be greater for a longer ray path. Therefore, to suppress the effect of data errors in a least-squares solution, a data confidence matrix is used in practice where the weighting is set logically based on the vertical offset. When a model constraint is adopted in the inversion to seek a solution with least deviation from some prescribed background that is most likely to have no spurious structure, a trade-off parameter is used to explicitly balance the dependence of the inversion solution to the data contribution and the reference model. The latter is built by combining sonic logging information, which is hard geological evidence at the vicinity of wells, and an initial estimate from the travel time back-projection, a preliminary solution of the travel time tomography. Geological constraints are set so that the inversion solution should have the least deviation from the hard geological evidence, and more deviation for the remaining part of the survey region, since the true velocity model might differ from such an initial estimate and the true ray paths might deviate from the initial ray paths.
Date Issued
2005-06-01
Date Acceptance
2005-04-26
Citation
Journal of Geophysics and Engineering, 2005, 2 (2), pp.139-146
ISSN
1742-2132
Publisher
Oxford University Press (OUP)
Start Page
139
End Page
146
Journal / Book Title
Journal of Geophysics and Engineering
Volume
2
Issue
2
Copyright Statement
© 2005 Nanjing Institute of Geophysical Prospecting
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000230406200008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Geochemistry & Geophysics
seismic tomography
travel time inversion
inverse problem
inversion constraints
crosshole seismic
Publication Status
Published
Date Publish Online
2005-05-20