My research focuses on modeling of long-period seismic waveforms to improve imaging of 3D global and regional seismic velocity structure (click here for most recent model). In particular, the imaging of seismic anisotropy, the dependence of seismic velocity on the propagation direction and polarization of waves, on a global scale has revealed many intriguing connections with mantle dynamics. For example, a global anisotropic model developed through waveform modeling provides an explanation for the anomalously thick continental lithosphere suggested by many previous seismic velocity models as a signature of dynamically maintained anisotropy in the asthenosphere, a region of the mantle with reduced viscosity which accommodates the shear deformation of the motion of the rigid lithospheric plates. The model also showed anisotropic signatures associated with 200-300 km deep vertical flow beneath mid-ocean ridges, subducting slabs in the transition zone (400-700 km) and boundary layer flow at the core-mantle boundary layer. Interpreting these results requires an interdisciplinary approach linking, in particular, mineral physics, geodynamics, and seismology.
Multiple future avenues of research are suggested by this progress. For global-scale modeling, it is important to integrate different datasets with appropriate theoretical approaches, and I have been working for the last few years to include waveforms from previous modeling as well as extensive freely available and newly gathered travel time databases in modeling using a consistent finite-frequency framework. This will improve resolution, and allow for more ambitious anisotropic modeling on the global scale, as well as more in-depth exploration of regions highlighted through the global model. Further theoretical work is necessary for determining the modeling approach most likely to give us new insight into mantle dynamics.
Additionally, I am excited to apply my waveform modeling "toolbox" to work in collaboration with other researchers on a variety of projects. In particular, there is a lot of room for exciting work in planetary science. I'm currently involved as a member of the science team for a proposed mission to Mars called InSight. The overall mission proposal is spearheaded by PI Bruce Banerdt, and I am participating in the SEIS team, headed by Philippe Lognonné. As another example, I have collaborated in the past with Michael Manga and others at UC Berkeley providing instrument design aims for a proposed study of seismology on Europa and the other Galilean moons. Our work has produced some important modeling results for Europa's internal structure and the kinds of seismic data acquisition needed to determine it.