Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007geoji.171..847z&link_type=abstract
Geophysical Journal International, Volume 171, Issue 2, pp. 847-856.
Astronomy and Astrophysics
Astronomy
3
Finite-Frequency Tomography, Fréchet Kernels, Head Waves, Pn, Waveform Simulation
Scientific paper
Head waves are extremely important in determining the structure of the predominantly layered Earth. While several recent studies have shown the diffractive nature and the 3-D Fréchet kernels of finite-frequency turning waves, analogues of head waves in a continuous velocity structure, the finite-frequency effects and sensitivity kernels of head waves are yet to be carefully examined. We present the results of a numerical study focusing on the finite-frequency effects of head waves. Our model has a low-velocity layer over a high-velocity half-space and a cylindrical-shaped velocity perturbation placed beneath the interface at different locations. A 3-D finite-difference method is used to calculate synthetic waveforms. Traveltime and amplitude anomalies are measured by the cross-correlation of synthetic seismograms from models with and without the velocity perturbation and are compared to the 3-D sensitivity kernels constructed from full waveform simulations. The results show that the head wave arrival-time and amplitude are influenced by the velocity structure surrounding the ray path in a pattern that is consistent with the Fresnel zones. Unlike the `banana-doughnut' traveltime sensitivity kernels of turning waves, the traveltime sensitivity of the head wave along the ray path below the interface is weak, but non-zero. Below the ray path, the traveltime sensitivity reaches the maximum (absolute value) at a depth that depends on the wavelength and propagation distance. The sensitivity kernels vary with the vertical velocity gradient in the lower layer, but the variation is relatively small at short propagation distances when the vertical velocity gradient is within the range of the commonly accepted values. Finally, the depression or shoaling of the interface results in increased or decreased sensitivities, respectively, beneath the interface topography.
Shen Yang
Zhang Zhigang
Zhao Li
No associations
LandOfFree
Finite-frequency sensitivity kernels for head waves does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Finite-frequency sensitivity kernels for head waves, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Finite-frequency sensitivity kernels for head waves will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-740297