Travel time inversion: A geometrical approach

Garmany, Jan; Orcutt, John A.; Parker, Robert L.

doi:10.1029/jb084ib07p03615

Cited by 81 publications

(39 citation statements)

References 11 publications

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“…This would suggest only minor influences of CMB structure on individual paths. V p model for the outermost core τ − p inversion: effects of starting model KH2013 built a V p model of the topmost 700 km of the outer core using differential SmKS travel time anomalies of several Fiji-Tonga events recorded at Europe, dt 3−2 , dt 4−3 , and dt 5−3 , to which a τ − p inversion method had been applied (Garmany et al 1979;HK2010;KH2013), with PREM as the starting model. The resultant model, KHOMC, has a 0.45 % slower V p than PREM at the CMB Array distances correspond to approximate array centers, whose accurate value do not affect the results.…”

Section: Array Measurementsmentioning

confidence: 99%

Stratification of earth’s outermost core inferred from SmKS array data

Kaneshima

Matsuzawa

2015

Prog. in Earth and Planet. Sci.

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SmKS arrivals recorded by large-scale broadband seismometer arrays are analyzed to investigate the depth profile of P wave speed (V p ) in the outermost core. The V p structure of the upper 700 km of the outer core has been determined using SmKS waves of Fiji-Tonga events recorded at stations in Europe. According to a recent outer core model (KHOMC), the V p value is 0.45 % slower at the core mantle boundary (CMB) than produced by the Preliminary Reference Earth Model (PREM), and the slow anomaly gradually diminishes to insignificant values at ∼300 km below the CMB. In this study, after verifying these KHOMC features, we show that the differential travel times measured for SmKS waves that are recorded by other large-scale arrays sampling laterally different regions are well matched by KHOMC. We also show that KHOMC precisely fits the observed relative slowness values between S2KS, S3KS, and S4KS (SmKS waves with m = 2, 3, and 4). Based on these observations, we conclude that SmKS predominantly reflect the outer core structure. Then we evaluate biases of secondary importance which may be caused by mantle heterogeneity. The KHOMC V p profile can be characterized by a significant difference in the radial V p gradient between the shallower 300 km and the deeper part of the upper 700 km of the core. The shallower part has a V p gradient of −0.0018 s −1 , which is steeper by 0.0001 s −1 when compared to the deeper core presented by PREM. The steeper V p gradient anomaly of the uppermost core corresponds to a radial variation in the pressure derivative of the bulk modulus, K = dK/dP. The K value is 3.7, which is larger by about 0.2 than that of the deeper core. The radial variation in K is too large to have a purely thermal origin, according to recent ab initio calculations on liquid iron alloys, and thus requires a thick and compositionally stratified layering at the outermost outer core.

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Section: Array Measurementsmentioning

confidence: 99%

Stratification of earth’s outermost core inferred from SmKS array data

Kaneshima

Matsuzawa

2015

Prog. in Earth and Planet. Sci.

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“…which is reminiscent of the expression obtained by Garmany (1979) and Garmany et al (1979). The dependence on PI and P 2 is embedded in P 3' This mapping is simplest when Z is a single-valued function of P 3' For instance, this will be the case when the slowness surface shrinks with depth without changing its shape, as described by Garmany (I 988b) and Shearer .…”

Section: Delay Times and Radon Transform Synthesismentioning

confidence: 90%

A Student's Garden of Anisotropy

Garmany¹

1989

Annu. Rev. Earth Planet. Sci.

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“…First, for an undulating boundary there may be discontinuities in w(z), that is for small changes in the angle the x position of the boundary may change abruptly. This is much like the situation in traveltime inversion using the tau method (Bessonova et al 1974(Bessonova et al , 1976Garmany et al 1979). These discontinuities are also the source of non-uniqueness for the inverse problem, somewhat akin to low-velocity zones in traveltime inversion.…”

Section: Inversion Of Gravity Datamentioning

confidence: 93%

Groups, algebras, and the non-linearity of geophysical inverse problems

Vasco¹

1997

Geophysical Journal International

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S U M M A R YMathematical methods from the theory of continuous groups are used to determine whether a non-linear inverse problem, in the form of a functional, can be transformed into a linear inverse problem. If such transformations exist they can be constructed from the soiutions of a linear system of differential equations. A n illustration of the methodology is given by the linearization of the functional relating basement topography to observed surface gravity. The linearized inversion of gravity data for basement topography is applied to observations from Yucca Mountain, Nevada. A 2.0 k m step in the basement to the west of Yucca Mountain, corresponding to the Bare Mountain fault, matches the Bouguer gravity anomaly. The resolution and uncertainty associated with the estimates of basement topography indicate that the structure directly beneath the gravity line is well constrained.

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Travel time inversion: A geometrical approach

Cited by 81 publications

References 11 publications

Stratification of earth’s outermost core inferred from SmKS array data

Stratification of earth’s outermost core inferred from SmKS array data

A Student's Garden of Anisotropy

Groups, algebras, and the non-linearity of geophysical inverse problems

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