Nissen-Meyer Home

Department of Geosciences 
312 Guyot Hall 
Princeton University 
Princeton, NJ 08544

Phone: (609) 258-1504
E-Mail: tarje [at] princeton.edu

Advisors: Tony Dahlen, Guust Nolet

Summary. Global seismology, i.e. the endeavour to utilize seismic energy to image and constrain the Earth's 3-D structure, composition and dynamics, has tremendously benefitted from several advances in the recent past such as global wave propagation methods, high-quality broadband data, and improved inversion techniques. One example of the inversion issue has gained considerable attention inasmuch as it includes the wave character in defining the sensitivity of propagating seismic waves due to potential scattering anywhere along its way, rather than collapsing the region of sensitivity onto an infinitely thin "ray path". Currently, the kernels for this approach are however calculated using ray theory for each desired seismic phase, but cannot account for diffracted or triplicated phases. Our objective is to compute complete sensitivity kernels for the full wavefield based on forward modeling.

During my PhD, I am developing the axisymmetric spectral-element method for elastodynamics, which is well suited to eventually calculate those kernels at high frequencies by reducing the full 3-D problem to a computationally tractable series of 2-D disks. We demonstrate the efficiency and high accuracy of this approach by validation against various reference solutions (normal mode summation, analytical radiation). The parallelized algorithm can at this point handle full 3-D seismic moment-tensor sources in a homogeneous or multilayered solid sphere. Work in progress includes an advanced technique for optimally flexible parallelization, the fluid discretization and inclusion of 1-D background models. Upon algorithmic completion, topics of interest include sensitivity studies of the lowermost mantle with a natural focus on very high-frequency diffracted energy and tomographic traveltime inversion of a region well sampled by core-grazing arrivals.

For more more details, see "Research" on my homepage.