Finite-Frequency Tomography
In traditional seismic tomography, the propagation of a seismic wave has been treated as a thin ray. This is valid strictly only in the limit of infinite frequency. The observed seismic waves have a finite frequency range. We recently developed a finite frequency tomographic method that utilizes the 3D sensitivity kernels of finite-frequency travel times.

Depth of Origin of the Iceland Hotspot
Three decades after Morgan proposed that hotspots are associated with upwelling mantle plumes, it is still debated whether plumes originate from the lower mantle or from a convective instability at the base of the upper mantle near 660 km depth. We address the problem using a new approach. (more )

Depths of Melting beneath Mid-Ocean Ridges
Enrichment of the mantle source has a significant influence on major element composition of mid-ocean ridge basalts. We showed that in normal ridges away from hotspots, there is an almost uniform onset of melting, while the final depth of melting is variable. This points to a nearly uniform temperature within the upwelling asthenosphere and strong influence of the cooling from the surface. (more )