Conclusion

Using a synthetic dataset of long period fundamental and high mode waveforms, we have quantified the contamination of mantle structure arising from the use of linear crustal corrections, which are inadequate at modeling the effects of crustal structure on waveforms, especially for the transverse component. Models derived using approximate forward modeling techniques may suffer from artifacts at depths of 0 - 100 km. that arise from unmodelled crustal effects. Under Tibet, the contamination may extend to 200 km. These artifacts can be eliminated by inverting for Moho and seafloor topography/bathymetry; however, the retrieved perturbations are unphysical. In this study, we have examined the effects of linear crustal corrections, in which a single set of kernels is used. A much more accurate, though computationally heavy, approach involves non-linear crustal corrections, in which laterally varying structure kernels are considered along each path (e.g Montagner and Jobert, 1988).

Figure 2.60: Isotropic shear wave speed model derived from synthetic transverse-component long-period fundamental mode surface wave and overtone waveforms. The starting model is a 1D mantle model with 3D crustal structure.Note the depth extent and tectonic nature of the retrieved artificial structure Accounting for perturbations in Moho topography in the inversion removes this contamination.
\begin{figure}\begin{center}
\epsfig{file=Lekic07_2, width=8cm}\end{center}\end{figure}

Berkeley Seismological Laboratory
215 McCone Hall, UC Berkeley, Berkeley, CA 94720-4760
Questions or comments? Send e-mail: www@seismo.berkeley.edu
© 2007, The Regents of the University of California