Seismic waves can be used to improve three-dimensional (3D) images of Earth's interior. These images provide a starting point for understanding (1) the present thermal and compositional structure of the Earth, and (2) the past and future evolution of the Earth. With better images, we are able to provide more accurate simulations of earthquake ground motion, which facilitates better assessment of seismic hazard.

My PhD thesis involved developing --- along with collaborators Jeroen Tromp and Qinya Liu --- a seismic tomographic technique that employs accurate earthquake simulations performed on supercomputers. Two papers illustrate the theoretical background of the technique and also demonstrate how it works using synthetic examples (2005, 2007). Two papers show applications of the tomographic technique to southern California, where very strong (+/- 30%) variations are applied to an initial 3D model in order to better fit full-length three-component seismograms (Science 2009, Geophysical Journal International 2010).

1. My PhD thesis (PDF format) can be downloaded from the Caltech library here. Download the full thesis as 00_CarlTapePhDThesis.pdf, or pick a particular section.
2. Article in Geophysical Journal International (2010) by Tape, Liu, Maggi, Tromp: Seismic tomography of the southern California crust based on spectral-element and adjoint methods (PDF)
3. Article in Science (2009) by Tape, Liu, Maggi, Tromp: Adjoint tomography of the southern California crust (PDF) Supplemental Material (PDF)
4. Article that summarizes the research published in Science: Scanning the Land, by Sid Perkins, Science News
5. Explore a nice interactive website made by Faria Chowdhury at the Southern California Earthquake Data Center at Caltech. Click around to view our tomographic model ("m16") of the southern California crust.
6. The crustal model m16, along with all seismograms and plotted comparisons. All files are here; first read the instructions in m16_info.pdf (See also point 3 below.)

Additional links:

1. Two software packages used within our studies can be found at the Computational Infrastructure for Geodynamics (CIG) : SPECFEM3D -- a seismic wave propagation code (Dimitri Komatitsch and Jeroen Tromp) FLEXWIN -- a code for automated time-window selection for seismograms (Alessia Maggi et al.)
2. SCEC website about CVM-H. The CVM-H 6.2 model included the crustal model m16 of Tape et al. (2009). CVM-H is led by the Harvard structural geology group.