DSM complete synthetic seismograms: SH, spherically symmetric, case

Cummins, P. R.

doi:10.1029/94gl00013a

Cited by 14 publications

(18 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…S2 in Supplementary Information). We also obtained the corresponding differential travel times in model PREM by the same procedure using synthetic waveforms calculated by the direct-solution method242526 (DSM). Comparison between observed and model-predicted differential travel times clearly suggests that the velocity at the top of the core in PREM needs to be lowered (Fig.…”

Section: Measuring S3ks-skks Differential Travel Timesmentioning

confidence: 99%

Seismological evidence for a non-monotonic velocity gradient in the topmost outer core

Tang

Zhao

Hung

2015

Sci Rep

View full text Add to dashboard Cite

The Earth's core is mostly an Fe-Ni alloy with a fraction of light elements (~10 wt%, mainly O, S and Si). Accumulation of these light elements under the core-mantle boundary (CMB) may lead to chemical stratification. Seismic observations have been presented both for and against the stratification in the topmost region of the outer core. Here we investigate the structure under the CMB using differential travel times between SKKS and S3KS waves. We obtain 606 high-quality S3KS-SKKS differential travel times with global path coverage. Result from a Bayesian inversion of these differential times indicates that the seismic velocity in the top 800 km of the outer core is ~0.07% on average lower than that in model PREM. The depth-dependent velocity profile, in particular a low-velocity zone of up to ~0.25% lower than PREM at ~80 km below the CMB, strongly favors the existence of stratification at the top of the outer core.

show abstract

Section: Measuring S3ks-skks Differential Travel Timesmentioning

confidence: 99%

Seismological evidence for a non-monotonic velocity gradient in the topmost outer core

Tang

Zhao

Hung

2015

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Similarly, for a point force and z 0 = n Δ z +ε (ε→ 0), we can readily show that the solution obtained using is the same (to O (Δ z 2 )) as the solution obtained for dislocations (displacement discontinuities) with weights of 1/12, 10/12 and 1/12 at z = ( n − 1)Δ z , z = n Δ z and z = ( n + 1)Δ z , respectively. It can also be shown that the source representation of Cummins et al (1994) gives the same solution to O (Δ z 2 ) when optimally accurate operators are used.…”

Section: Source Representationmentioning

confidence: 99%

“…Vertical lines show the location of numerical nodes. The error of synthetics computed for sources at nodes by the source representation of Cummins et al (1994) (crosses) is also shown. Optimally accurate operators are used for all cases.…”

Section: Numerical Examplesmentioning

confidence: 99%

Accurate numerical methods for solving the elastic equation of motion for arbitrary source locations

Takeuchi

Geller²

2003

Geophysical Journal International

View full text Add to dashboard Cite

SUMMARY In our previous studies we derived a general criterion for optimally accurate numerical operators for computing synthetic seismograms. In this paper we extend our results by deriving source representations that are ‘tuned’ to match the errors of the numerical operators, so that optimally accurate synthetic seismograms are obtained. The same accuracy can be obtained whether the sources are at nodes of the numerical grid or between nodes. The accuracy of the synthetic seismograms is confirmed by numerical experiments. These results should facilitate inversion of seismic waveform data for 3‐D Earth structure and earthquake source parameters.

show abstract

“…Using a Galerkin approximation, the trial and the weight functions are chosen to be the tensor product of linear splines in the radial direction and generalized spherical harmonics basis functions. Cummins et al (1994a,b) and Geller & Ohminato (1994) used the direct solution method (DSM) to compute synthetic seismograms for laterally homogeneous media in spherical coordinates. In this case, there is no coupling between the toroidal and the spheroidal modes.…”

Section: Introductionmentioning

confidence: 99%

Coupling the spectral element method with a modal solution for elastic wave propagation in global earth models

Capdeville

Chaljub

Montagner

2003

Geophysical Journal International

129

104

View full text Add to dashboard Cite

International audienceWe present a new method for wave propagation in global earth models based upon the coupling between the spectral element method and a modal solution method. The Earth is decomposed into two parts, an outer shell with 3-D lateral heterogeneities and an inner sphere with only spherically symmetric heterogeneities. Depending on the problem, the outer heterogeneous shell can be mapped as the whole mantle or restricted only to the upper mantle or the crust. In the outer shell, the solution is sought in terms of the spectral element method, which stem from a high order variational formulation in space and a second-order explicit scheme in time. In the inner sphere, the solution is sought in terms of a modal solution in frequency after expansion on the spherical harmonics basis. The spectral element method combines the geometrical flexibility of finite element methods with the exponential convergence rate of spectral methods. It avoids the pole problems and allows for local mesh refinement, using a non-conforming discretization, for the resolution of sharp variations and topography along interfaces. The modal solution allows for an accurate isotropic representation in the inner sphere. The coupling is introduced within the spectral element method via a Dirichlet-to-Neumann (DtN) operator. The operator is explicitly constructed in frequency and in generalized spherical harmonics. The inverse transform in space and time requires special attention and an asymptotic regularization. The coupled method allows a significant speed-up in the simulation of the wave propagation in earth models. For spherically symmetric earth model, the method is shown to have the accuracy of spectral transform methods and allow the resolution of wavefield propagation, in 3-D laterally heterogeneous models, without any perturbation hypothesis

show abstract

DSM complete synthetic seismograms: SH, spherically symmetric, case

Cited by 14 publications

References 0 publications

Seismological evidence for a non-monotonic velocity gradient in the topmost outer core

Seismological evidence for a non-monotonic velocity gradient in the topmost outer core

Accurate numerical methods for solving the elastic equation of motion for arbitrary source locations

Coupling the spectral element method with a modal solution for elastic wave propagation in global earth models

Contact Info

Product

Resources

About