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Seismic velocity estimation from tim...

Cameron, Maria Kourkina.

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Seismic velocity estimation from time migration.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Seismic velocity estimation from time migration./
作者:	Cameron, Maria Kourkina.
面頁冊數:	102 p.
附註:	Source: Dissertation Abstracts International, Volume: 68-08, Section: B, page: 5271.
Contained By:	Dissertation Abstracts International68-08B.
標題:	Mathematics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3279620
ISBN:	9780549209300

Seismic velocity estimation from time migration.
Cameron, Maria Kourkina.

Seismic velocity estimation from time migration. - 102 p.

Source: Dissertation Abstracts International, Volume: 68-08, Section: B, page: 5271.

Thesis (Ph.D.)--University of California, Berkeley, 2007.

This item must not be sold to any third party vendors.

This is concerned with imaging and wave propagation in nonhomogeneous media, and includes a collection of computational techniques, such as level set methods with material transport, Dijkstra-like Hamilton-Jacobi solvers for first arrival Eikonal equations and techniques for data smoothing. The theoretical components include aspects of seismic ray theory, and the results rely on careful comparison with experiment and incorporation as input into large production-style geophysical processing codes.

ISBN: 9780549209300Subjects--Topical Terms:

515831
Mathematics.

Seismic velocity estimation from time migration.
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100 1 $a Cameron, Maria Kourkina. $3 3175357
245 1 0 $a Seismic velocity estimation from time migration.
300 $a 102 p.
500 $a Source: Dissertation Abstracts International, Volume: 68-08, Section: B, page: 5271.
500 $a Adviser: James Sethian.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2007.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be added to any third party search indexes.
520 $a This is concerned with imaging and wave propagation in nonhomogeneous media, and includes a collection of computational techniques, such as level set methods with material transport, Dijkstra-like Hamilton-Jacobi solvers for first arrival Eikonal equations and techniques for data smoothing. The theoretical components include aspects of seismic ray theory, and the results rely on careful comparison with experiment and incorporation as input into large production-style geophysical processing codes.
520 $a Producing an accurate image of the Earth's interior is a challenging aspect of oil recovery and earthquake analysis. The ultimate computational goal, which is to accurately produce a detailed interior map of the Earth's makeup on the basis of external soundings and measurements, is currently out of reach for several reasons. First, although vast amounts of data have been obtained in some regions, this has not been done uniformly, and the data contain noise and artifacts. Simply sifting through the data is a massive computational job. Second, the fundamental inverse problem, namely to deduce the local sound speeds of the earth that give rise to measured reflected signals, is exceedingly difficult: shadow zones and complex structures can make for ill-posed problems, and require vast computational resources.
520 $a Nonetheless, seismic imaging is a crucial part of the oil and gas industry. Typically, one makes assumptions about the earth's substructure (such as laterally homogeneous layering), and then uses this model as input to an iterative procedure to build perturbations that more closely satisfy the measured data. Such models often break down when the material substructure is significantly complex: not surprisingly, this is often where the most interesting geological features lie.
520 $a Data often come in a particular, somewhat non-physical coordinate system, known as time migration coordinates. The construction of substructure models from these data is less and less reliable as the earth becomes horizontally nonconstant. Even mild lateral velocity variations can significantly distort subsurface structures on the time migrated images. Conversely, depth migration provides the potential for more accurate reconstructions, since it can handle significant lateral variations. However, this approach requires good input data, known as a "velocity model".
520 $a We address the problem of estimating seismic velocities inside the earth, i.e., the problem of constructing a velocity model, which is necessary for obtaining seismic images in regular Cartesian coordinates. The main goals are to develop algorithms to convert time-migration velocities to true seismic velocities, and to convert time-migrated images to depth images in regular Cartesian coordinates.
520 $a Our main results are three-fold. First, we establish a theoretical relation between the true seismic velocities and the "time migration velocities" using the paraxial ray tracing. Second, we formulate an appropriate inverse problem describing the relation between time migration velocities and depth velocities, and show that this problem is mathematically ill-posed, i.e., unstable to small perturbations.
520 $a Third, we develop numerical algorithms to solve regularized versions of these equations which can be used to recover smoothed velocity variations. Our algorithms consist of efficient time-to-depth conversion algorithms, based on Dijkstra-like Fast Marching Methods, as well as level set and ray tracing algorithms for transforming Dix velocities into seismic velocities. Our algorithms are applied to both two-dimensional and three-dimensional problems, and we test them on a collection of both synthetic examples and field data.
590 $a School code: 0028.
650 4 $a Mathematics. $3 515831
650 4 $a Geophysics. $3 535228
690 $a 0405
690 $a 0373
710 2 $a University of California, Berkeley. $3 687832
773 0 $t Dissertation Abstracts International $g 68-08B.
790 $a 0028
791 $a Ph.D.
792 $a 2007
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3279620