High Resolution Imaging of Seismic Velocity Discontinuities

Funded by the NSF (NSF Award Abstract #0106904)

Principal Investigator: Anne Sheehan

Project Summary

Seismic estimates of existence and depth distribution of crust and mantle discontinuities are important for constraining models of composition, rheology, and temperature in the Earth. This project includes development, testing, and application of new methods for receiver function imaging. A Kirchhoff-style migration methodology which utilizes a point-scattering approach to handle nonplanar and laterally discontinuous interfaces has been developed. An uncertainty in this analysis is the biasing effects of three-dimensional discontinuity structure that could falsely project features into two-dimensional models. The migration inversion will be extended to three dimensions, and include back-scattered energy. Proper evaluation of the accuracy and resolution of these P/SV migration methods will require development of a synthetic seismogram method that can handle 3-D discontinuity topography and velocity heterogeneity and which will include all converted phases and surface reflections. A hybrid method will be implemented that will use ray theory to propagate a P wavefront to a finite difference grid that will span the region between the discontinuities and the surface. These techniques will be applied to regional data sets from the southwest Pacific and eastern California. These efforts are of great utility with appropriate data sets today and will become increasingly important with data sets that will be generated by the proposed USArray and similar projects.

Figures

Figure 1. Schematic illustration of geometry used in migration inversion.

Figure 2. Synthetic experiments with migration seismic processing of receiver functions.

Figure 3. Tonga common midpoint receiver function images.

Figure 4. Location map for Coso Passive Seismic Array

Figure 5. Sample Coso common midpoint receiver function east-west profile.