Validation of ray and wave theoretical travel times in heterogeneous random media
Resource
GEOPHYSICAL RESEARCH LETTERS 32: L20302
Journal
Geophysical research letters
Journal Volume
32
Journal Issue
20
Date Issued
2005
Author(s)
Yang, Hsin-Ying
Abstract
We investigate the validity of three theories of seismic tomography by numerical comparison of cross‐correlation travel time shifts of acoustic waves with their theoretical predictions in 3‐D heterogeneous random media. Whenever the characteristic heterogeneity scale length is shorter than half of the first Fresnel zone width, ray‐theoretical travel times yield large discrepancies from the cross‐correlation measurements. Born‐Fréchet kernel theory is valid for small‐scale structures but restricted to weak velocity perturbations. With increasing perturbation strength, neglecting the nonlinearity due to wave path bending in linearized ray and Born theories is no longer eligible. General ray theory accounts for the detour least‐time paths in strongly heterogeneous media, which prominently improves the predicted travel times for intermediate to large scale velocity variations.
Type
journal article
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