Calibration of Wavelength-Dependent Velocity Smoothing for Calculating a Frequency-Dependent traveltime
Abstract
Traveltime tomography is widely used to estimate the velocity structure of the Earth on all scales. Until recently, the forward modeling component of traveltime tomography has always been ray theory, an infinite frequency approximation of wave propagation. For near-surface studies there is a strong potential for ray theory to be invalid given typical seismic wavelengths and the length scales of shallow heterogeneities. A new form of traveltime tomography that takes the finite frequency of the data into account in both the forward and inverse modeling yields improved spatial resolution and more accurate estimation of velocity. Frequency-dependent traveltime tomography (FDTT) calculates frequency-dependent traveltimes, wave paths, and sensitivity kernels, which is implemented through the wavelength-dependent velocity smoothing (WDVS) algorithm. Given the width of the sensitivity kernels, it is possible to perform stable traveltime tomography with little or no smoothing regularization and thereby allow the data alone to determine the model structure. Fundamentally, this improvement is because the physics of wave propagation is more accurately considered through the WDVS algorithm. A calibration of WDVS with a full wavefield algorithm will be presented. Velocity models are carefully designed to capture the wavefront defined by the frequency-dependent traveltime from a plane wave source. This will be compared with a wavefront generated by a full wavefield method using the same velocity models and plane wave. Some applications of FDTT to realistic synthetic and real P- and SH-wave data will also be presented.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMNS13B1613C
- Keywords:
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- 7270 SEISMOLOGY / Tomography