The inclusion of intermediate depth earthquakes allows the deeper regions of the model to be resolved.
Results show extremely large variability in upper mantle structure in the Southwest Pacific.
Substantial velocity heterogeneity extends to deeper depth. Results also show a velocity discontinuity or very large velocity gradient near 220 km depth. The exceptionally low seismic velocities in the back arc regions rank among the lowest upper mantle velocities in the world. We also investigate the crustal structure of Fiji platform using both linearized and genetic algorithms inversion of receiver functions from local deep events. The receiver function analysis suggests crustal thicknesses beneath the stations of 22 - 28 km.