Lateral variations in mantle velocity structure and discontinuities determined from P, PP, S, SS, and SS — SdS travel time residuals

Vasco, D. W.; Johnson, Lane R.; Pulliam, J.

doi:10.1029/95jb00150

Cited by 48 publications

(49 citation statements)

References 55 publications

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“…[1994] was extended to include internally reflected PP and SS phases as well as underside reflections off the 410 and 660 km discontinuities to examine the possible trade-off between volumetric heterogeneity and the boundary deflections on these interfaces [Vasco et al, 1995a]. They found that P and S velocity estimates are not significantly contaminated by boundary topography of the order of 30 km.…”

Section: Introductionmentioning

confidence: 99%

Whole Earth structure estimated from seismic arrival times

Vasco¹,

Johnson²

1998

J. Geophys. Res.

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131

125

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Section: Introductionmentioning

confidence: 99%

Whole Earth structure estimated from seismic arrival times

Vasco¹,

Johnson²

1998

J. Geophys. Res.

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131

125

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“…To improve sampling, Vasco and co workers Vasco et al 1993Vasco et al , 1994Vasco et al , 1995a used ISC data from a large range of seismic phases. Their most recent P wave model is based on P, PP, PKP^B, PKPBc, PKPr)F, and PcP (absolute) travel time residuals [Vasco and Johnson, 1998].…”

Section: Introductionmentioning

confidence: 99%

Tomographic imaging of the lowermost mantle with differential times of refracted and diffracted core phases (PKP, Pdiff)

Kárason¹,

Hilst²

2001

J. Geophys. Res.

172

167

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Abstract. The mapping of variations in P wave speed in the deep mantle is restricted by the uneven sampling of P waves, in particular beneath the Southern Hemisphere. To enhance data coverage, we augmented the • 1.6 million summary rays of P, pP, and pwP that we used in previous studies with differential travel times of diffracted and refracted core phases. For the core-refracted differential travel time residuals (PKP^e-PKPr)v and PKP^•3-PKP•3c) we used 1383 cross-correlated digital waveforms as well as •27,000 routinely processed bulletin data. We used the waveform data to define quality criteria for the selection and reduction of the bulletin PKP data. For PKPDF-Pdiff we only considered 543 records derived from waveform cross correlation. No PcP data were used in this study. We used optical ray theory to calculate the ray paths associated with the P, pP, pwP, and PKP data, which are measured at 1 Hz. However, to account for the large Fresnel zones of the low-frequency (•50 mHz) PKPDF-Pdiff data we estimated the three-dimensional shape of the Fr6chet sensitivity kernels from kernels calculated by normal mode summation. The use of these kernels allows us to properly distribute the sensitivity for a given seismic phase over a large mantle volume while allowing the high-frequency data to constrain small-scale structure. The differential times are relatively insensitive to source mislocation and to structure in the shallow mantle beneath source and receivers, and they have previously been interpreted exclusively in terms of lateral structure directly above the core mantle boundary (CMB). However, images thus obtained can be contaminated by effects of small scale structure elsewhere in the mantle. Here, we do not make a priori assumptions about the mantle source of anomalous time differentials. From test inversions we conclude that (both upper and lower) mantle structures that are poorly resolved by P data can be mapped into the core along PKP paths but that the effect of outer core structures, if any, on the mantle model is small. Compared to the inversion of the P, pP, and pwP alone, the inclusion of the PKPA•-PKPr)• and PKPA•-PKP•c and PKPr)v-Pdifr data improves the resolution of structure beneath 2200 km depth. In particular, the joint inversion puts better constraints on the long-wavelength variations in the very deep mantle and yields an increase in the amplitude of velocity perturbations near the CMB that is in agreement with but still smaller than inferences from shear wave studies. Resolution tests indicate that in some regions the enhanced definition of structure is significant, but in most regions the improvements are subtle and structure remains poorly resolved in large regions of the mantle.

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“…Although most travel-time tomography studies use the first P-and S-wave arrivals, some researchers have used later-phase data (i.e., reflected and converted waves) to determine velocity tomography at both the local scale (e.g., Zhao et al 1992Zhao et al , 2005Xia et al 2007;Gupta et al 2009) and the global scale (e.g., Vasco et al 1995, Zhao 2001bZhao et al 2013). It is found that the later-phase data are very useful in tomographic imaging, because they sample the Earth's structure in areas which are not well sampled by the first P-and S-waves.…”

Section: Velocity Tomography Methodsmentioning

confidence: 99%

Methodology of Seismic Tomography

Zhao

2015

Multiscale Seismic Tomography

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In this chapter, we introduce the tomographic methods which are widely used to study three-dimensional (3-D) seismic velocity, attenuation and anisotropy structures of the Earth's interior. The fundamental mathematical equations of these methods are presented for a better understanding of the principles of seismic tomography.Keywords Seismic tomography · Model parameterization · Ray tracing · Inversion · Resolution · Damping parameter From seismological observations, such as P-and S-wave arrival times, amplitudes, and waveforms, basically three kinds of physical parameters can be determined to characterize the seismological structure of the Earth's interior. These parameters are seismic velocity, attenuation, and anisotropy. Applying tomographic methods to the seismological data, we can estimate the three-dimensional (3-D) distribution of these parameters, i.e., seismic velocity tomography, attenuation tomography, and anisotropy tomography. In this chapter, we introduce the general approaches to conduct the three kinds of tomographic inversions.In general, a study of seismic tomography includes the following operations: (1) Modeling the Earth's interior structure, i.e., model parameterization; (2) Forward modeling, such as ray tracing in travel-time tomography, earthquake relocation, and the construction of observation equations; (3) Inversion, i.e., solving the large system of observation equations; and (4) Resolution and error analysis, i.e., evaluating the resolution and uncertainty of the obtained tomographic image. Seismic Velocity TomographySince the advent of seismology, P-and S-wave velocities (Vp, Vs) have been the primary physical parameters to characterize the Earth's structure because they are determined mainly from P-and S-wave arrival-time data which can be measured in high quality and great quantity by the routine processing of seismic networks deployed in many regions. Hence, earthquake arrival times have been the most

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Lateral variations in mantle velocity structure and discontinuities determined from P, PP, S, SS, and SS — S_dS travel time residuals

Cited by 48 publications

References 55 publications

Whole Earth structure estimated from seismic arrival times

Whole Earth structure estimated from seismic arrival times

Tomographic imaging of the lowermost mantle with differential times of refracted and diffracted core phases (PKP, Pdiff)

Methodology of Seismic Tomography

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