Carnegie Fellow Daoyuan Sun arrived at DTM this week. While receiving his Ph.D. at Caltech, Sun studied seismic wave propagation and the fine structures of the lower mantle. In particular, his research focused on mapping the structure of the core-mantle boundary, including the D” layer, plumes, and large low-velocity provinces. With waveform modeling for S wave triplication data beneath Central America, Sun, along with Caltech’s geodynamics group, was able to develop D” discontinuity models by assuming that this discontinuity is related to phase changes. Predictions from this model explain the observed unstable nature of S wave triplication.

The group was also able to perform a mapping of dynamic models (temperature, chemistry, and phase) into P and S velocity variations. Synthetic seismograms generated for these dynamic models were then compared directly with corresponding seismic observations. Their results suggest that a high-bulk-modulus dynamic model is a candidate to explain the African large low-shear-velocity province. Sun and colleagues recently developed a new tool, a multi-pathing detector (MPD), which emphasizes coherent waveform distortion patterns in array data. The tool is particularly useful in detecting sharp structures in the deep Earth. The group has begun to apply MPD to USArray data, attempting to map out sharp upper mantle features beneath the western United States. At DTM, Sun plans to continue mapping sharp features with USArray and other PASSCAL data, and he is interested in determining the shape, sharpness, and origin of the plume-like structures beneath Yellowstone and Hawaii.