The goal of my research is to accurately image and characterize subsurface structures in seismically difficult areas, with high-resolution experiments. I constrain these inversions with independent geophysical and geological data. The seismic imaging, tomography, and monte-carlo optimization techniques I develop improve the productivity of resource exploration and development, and of hazards assessments. In particular I try to describe the characteristics of earthquake faults and of sites in order to mitigate seismic hazards to life and property.