The Born approximation gives a linear relation between perturbation and change of the wavefield. In our case the reference model is the spherically symmetric Earth and we use an exact Green function to evaluate the wavefield perturbation by integration over the heterogeneities. Born scattering of long-period body waves. With PREM as reference Earth model and the Harvard CMT solutions , we compute PREM synthetic P diff waveforms and subtract them from the data. Since we use the Born approximation to model the displacement field, the inverse problem is linear.
Path coverage is best across the Northern Pacific.
We see two marked low velocity regions under the Pacific that correlate well with the Hawaii hotspot and the Austral Seamount Chain. There is also some correlation with ultra-low velocity zones. Born scattering of long-period body waves. Computation of exact Green's Functions for the elastodynamic equation of a spherically symmetric Earth model, offering an alternative to the Normal Mode and Reflectivity approaches. The Green's Function for the elastodynamic equation of a spherically symmetric Earth model is constructed directly in the frequency domain by expanding the displacement field into vector spherical harmonics and solving an inhomogeneous system of ordinary first-order differential equations.