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| Titel |
Constraining fault interpretation through tomographic velocity gradients: application to northern Cascadia |
| VerfasserIn |
K. Ramachandran |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 3, no. 1 ; Nr. 3, no. 1 (2012-02-16), S.53-61 |
| Datensatznummer |
250000835
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| Publikation (Nr.) |
 copernicus.org/se-3-53-2012.pdf |
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| Zusammenfassung |
| Spatial gradients of tomographic velocities are seldom used in
interpretation of subsurface fault structures. This study shows that spatial
velocity gradients can be used effectively in identifying subsurface
discontinuities in the horizontal and vertical directions. Three-dimensional
velocity models constructed through tomographic inversion of active source
and/or earthquake traveltime data are generally built from an initial 1-D
velocity model that varies only with depth. Regularized tomographic
inversion algorithms impose constraints on the roughness of the model that
help to stabilize the inversion process. Final velocity models obtained from
regularized tomographic inversions have smooth three-dimensional structures
that are required by the data. Final velocity models are usually analyzed
and interpreted either as a perturbation velocity model or as an absolute
velocity model. Compared to perturbation velocity model, absolute velocity
models have an advantage of providing constraints on lithology. Both
velocity models lack the ability to provide sharp constraints on subsurface
faults. An interpretational approach utilizing spatial velocity gradients
applied to northern Cascadia shows that subsurface faults that are not
clearly interpretable from velocity model plots can be identified by sharp
contrasts in velocity gradient plots. This interpretation resulted in
inferring the locations of the Tacoma, Seattle, Southern Whidbey Island, and
Darrington Devil's Mountain faults much more clearly. The Coast Range
Boundary fault, previously hypothesized on the basis of sedimentological and
tectonic observations, is inferred clearly from the gradient plots. Many of
the fault locations imaged from gradient data correlate with earthquake
hypocenters, indicating their seismogenic nature. |
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