Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000geoji.141..558z&link_type=abstract
Geophysical Journal International, Volume 141, Issue 3, pp. 558-576.
Astronomy and Astrophysics
Astronomy
66
Body Waves, Fréchet Derivatives, Normal Modes, Ray Theory, Traveltime, Wave Propagation
Scientific paper
Seismic traveltimes are the most widely exploited data in seismology. Their Fréchet or sensitivity kernels are important tools in tomographic inversions based on the Born or single-scattering approximation. The current study is motivated by a paradox posed by two seemingly irreconcilable observations in the numerical calculations for the sensitivity kernels of the traveltime perturbations. Calculations of kernels for 2-D media by the normal-mode approach indicate that traveltimes are most sensitive to the structure on and around the geometrical ray paths corresponding to the seismic arrivals, whereas calculations for 3-D media by geometrical ray theory predict exactly zero sensitivities on the ray paths. In the current work, we employ these two completely different wave-propagation approaches, the more efficient geometrical ray theory and the more accurate normal-mode theory, to investigate the 3-D sensitivities of the delay times to shear-wave speed variations. Expressions for the delay-time Fréchet kernels are presented for both methods, and extensive numerical experiments are conducted for various types of seismic phases as well as for different reference earth models. The results show that the contradictory observations are but two examples of a wide range of behaviours in the delay-time sensitivity. For most of the seismic phases in realistic reference models with multiple discontinuities, wave-speed gradients and low-velocity zones, the wavefields are highly complicated and ray theory, which describes the response by the contributions of a few geometrical rays between the source and receiver, produces qualitatively different delay-time kernels from those obtained by the normal-mode theory, which includes essentially all contributions.
Chapman Chris H.
Jordan Thomas H.
Zhao Li
No associations
LandOfFree
Three-dimensional Fréchet differential kernels for seismicdelay times 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 Three-dimensional Fréchet differential kernels for seismicdelay times, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Three-dimensional Fréchet differential kernels for seismicdelay times will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1348421