Nonuniqueness in traveltime tomography: Ensemble inference and cluster analysis

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · Geophysics

DOI:https://doi.org/10.1190/1.1444040· OSTI ID:277618

Vasco, D W; Peterson, Jr, J E; Majer, E L ^[1]

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1. Lawrence Berkeley Lab., CA (United States). Center for Computational Seismology

The authors examine the nonlinear aspects of seismic traveltime tomography. This is accomplished by completing an extensive set of conjugate gradient inversions on a parallel virtual machine, with each initiated by a different starting model. The goal is an exploratory analysis of a set of conjugate gradient solutions to the traveltime tomography problem. The authors find that distinct local minima are generated when prior constraints are imposed on traveltime tomographic inverse problems. Methods from cluster analysis determine the number and location of the isolated solutions to the traveltime tomography problem. They apply the cluster analysis techniques to a cross-borehole traveltime data set gathered at the Gypsy Pilot Site in Pawnee County, Oklahoma. They find that the 1075 final models, satisfying the traveltime data and a model norm penalty, form up to 61 separate solutions. All solutions appear to contain a central low velocity zone bounded above and below by higher velocity layers. Such a structure agrees with well-logs, hydrological well tests, and a previous seismic inversion.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 277618
• Journal Information: Geophysics, Journal Name: Geophysics Journal Issue: 4 Vol. 61; ISSN GPYSA7; ISSN 0016-8033
• Country of Publication: United States
• Language: English

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