Depth imaging of crustal scale seismic reflection surveys in southern California

Advanced seismic reflection imaging techniques can be used to substantially improve the images obtained from deep crustal reflection surveys. This dissertation demonstrates this thesis via application of prestack wave equation migration to two crustal scale reflection surveys collected by the Los Angeles Regional Seismic Experiment (LARSE) in southern California.; Wave equation prestack depth imaging is an effective tool for imaging weak reflection energy in the presence of noise, primarily due to wavefield correlation used by this process. A secondary advantage is the ability to image each frequency component independently and form the image bandwidth after migration, allowing the optimal bandwidth to be more effectively determined.; Using tomographically generated crustal velocity models, the images of the LARSE lines produced here show substantial improvements over the previous imaging efforts. Coherent images of features as deep as the Moho are seen from both lines. Reflections from structures associated with major fault zones allow the subsurface locations of the San Andreas and San Gabriel fault zones to be inferred.; The depth images correlate well with teleseismic measurements of crustal thickness and gross crustal structure. The images also correlate well with the spatial distribution of local seismic activity. A strong correlation between reflectivity and local seismic activity suggests that faults or fault prone areas form a substantial portion of the observed reflectivity.; The new depth images show several previously unknown crustal features: thickening and discontinuities of the Moho associated with the San Andreas Fault, discontinuities in the Moho associated with the San Gabriel and Northridge fault systems, and a mid-crustal shear zone beneath the San Gabriel Mountains.