Global SH-wave propagation using a parallel axisymmetric spherical finite-difference scheme: Application to whole mantle scattering

SUMMARY We extended a high-order finite-difference scheme for the elastic SH-wave equation in axisymmetric media for use on parallel computers with distributed memory architecture. Moreover, we derive an analytical description of the implemented ring source and compare it quantitatively with a double couple source. The restriction to axisymmetry and the use of high performance computers and PC networks allows computation of synthetic seismograms at dominant periods down to 2.5 s for global mantle models. We give a description of our algorithm (SHaxi) and its verification against an analytical solution. As an application, we compute synthetic seismograms for global mantle models with additional stochastic perturbations applied to the background S-wave velocity model. We investigate the influence of the perturbations on the SH wavefield for a suite of models with varying perturbation amplitudes, correlation length scales, and spectral characteristics. The inclusion of stochastic perturbations in the models broadens the pulse width of teleseismic body wave arrivals and delays their peak arrival times. Coda wave energy is also generated which is observed as additional energy after prominent body wave arrivals. The SHaxi method has proven to be a valuable method for computing global synthetic seismograms at high frequencies and for studying the seismic waveform effects from models where rotational symmetry may be assumed.

[1]  F. Scherbaum,et al.  Acoustic simulation of P‐wave propagation in a heterogeneous spherical earth: numerical method and application to precursor waves to PKPdf , 2000 .

[2]  D. L. Anderson,et al.  Preliminary reference earth model , 1981 .

[3]  J. Cleary,et al.  Seismic Wave Scattering near the Core-Mantle Boundary: a New Interpretation of Precursors to PKP , 1972, Nature.

[4]  Luděk Klimeš,et al.  Correlation Functions of Random Media , 2002 .

[5]  D. Komatitsch,et al.  Introduction to the spectral element method for three-dimensional seismic wave propagation , 1999 .

[6]  Robert W. Graves,et al.  Simulating seismic wave propagation in 3D elastic media using staggered-grid finite differences , 1996, Bulletin of the Seismological Society of America.

[7]  Robert W. Clayton,et al.  Finite difference simulations of seismic scattering: Implications for the propagation of short‐period seismic waves in the crust and models of crustal heterogeneity , 1986 .

[8]  A. Levander.  Fourth-order finite-difference P-SV seismograms , 1988 .

[9]  Heiner Igel,et al.  Frequency-dependent effects on travel times and waveforms of long-period S and SS waves , 1997 .

[10]  F. Dahlen,et al.  Traveltime biases in random media and the S-wave discrepancy , 2004 .

[11]  Alexandre Fournier,et al.  A 2‐D spectral‐element method for computing spherical‐earth seismograms—II. Waves in solid–fluid media , 2008 .

[12]  Z. Alterman,et al.  Propagation of elastic waves in layered media by finite difference methods , 1968 .

[13]  B. Kennett,et al.  Seismic wavefield calculation for laterally heterogeneous whole earth models using the pseudospectral method , 1998 .

[14]  L. T. Ikelle,et al.  2-D random media with ellipsoidal autocorrelation functions , 1993 .

[15]  Won Sang Lee,et al.  Estimation of S‐wave scattering coefficient in the mantle from envelope characteristics before and after the ScS arrival , 2003 .

[16]  B. Romanowicz,et al.  The COSY Project: verification of global seismic modeling algorithms , 2000 .

[17]  Emmanuel Chaljub,et al.  Sensitivity of SS precursors to topography on the upper‐mantle 660‐km discontinuity , 1997 .

[18]  Jean Virieux,et al.  SH-wave propagation in heterogeneous media; velocity-stress finite-difference method , 1984 .

[19]  R. Benites,et al.  Coda Q as a Combination of Scattering and Intrinsic Attenuation: Numerical Simulations with the Boundary Integral Method , 1996 .

[20]  Gregory S. Wagner.  Numerical simulations of wave propagation in heterogeneous wave guides with implications for regional wave propagation and the nature of lithospheric heterogeneity , 1996, Bulletin of the Seismological Society of America.

[21]  G. Davies.  Stirring geochemistry in mantle convection models with stiff plates and slabs , 2002 .

[22]  T. Nissen‐Meyer,et al.  Wave propagation in 3D spherical sections: effects of subduction zones , 2002 .

[23]  Arthur Frankel,et al.  A review of numerical experiments on seismic wave scattering , 1989 .

[24]  Michael Fehler,et al.  Seismic Wave Propagation and Scattering in the Heterogeneous Earth , 2012 .

[25]  G. Nolet,et al.  Multiple scattering of high‐frequency seismic waves in the deep Earth: Modeling and numerical examples , 2003 .

[26]  Eric de Bazelaire,et al.  Numerical modelling of interface scattering of seismic wavefield from a random rough interface in an acoustic medium: comparison between 2D and 3D cases , 2005 .

[27]  Alexandre Fournier,et al.  A two‐dimensional spectral‐element method for computing spherical‐earth seismograms – I. Moment‐tensor source , 2007 .

[28]  C. Juhlin,et al.  Scattering attenuation: 2-D and 3-D finite difference simulations vs. theory , 2000 .

[29]  Heiner Igel,et al.  P‐SV wave propagation in the Earth's mantle using finite differences: Application to heterogeneous lowermost mantle structure , 1996 .

[30]  R. Hilst,et al.  Compositional heterogeneity in the bottom 1000 kilometers of Earth's mantle: toward a hybrid convection model , 1999, Science.

[31]  Heiner Igel,et al.  Wave propagation in three-dimensional spherical sections by the Chebyshev spectral method , 1999 .

[32]  Hiroshi Takenaka,et al.  2.5-D modelling of elastic waves using the pseudospectral method , 1996 .

[33]  K. Aki,et al.  Quantitative Seismology, 2nd Ed. , 2002 .

[34]  Heiner Igel,et al.  SH-wave propagation in the whole mantle using high-order finite differences , 1995 .

[35]  Hiroshi Takenaka,et al.  Quasi-spherical approach for seismic wave modeling in a 2-D slice of a global Earth model with lateral heterogeneity , 2005 .

[36]  M. Fehler,et al.  Simulating the Envelope of Scalar Waves in 2D Random Media Having Power-Law Spectra of Velocity Fluctuation , 2003 .

[37]  P. Shearer,et al.  Seismic evidence for small-scale heterogeneity throughout the Earth's mantle , 1997, Nature.

[38]  Robert W. Clayton,et al.  A finite-difference simulation of wave propagation in two-dimensional random media , 1984 .

[39]  Peter M. Shearer,et al.  The global short-period wavefield modelled with a Monte Carlo seismic phonon method , 2004 .

[40]  Heiner Igel,et al.  Seismic imaging of the laterally varying D″ region beneath the Cocos Plate , 2007 .

[41]  Vernon F. Cormier,et al.  D as a transition in the heterogeneity spectrum of the lowermost mantle , 2000 .

[42]  Wu Ru-Shan.  Attenuation of short period seismic waves due to scattering , 1982 .