The objective of the proposed work is to process and interpret seismic and GPR data to determine depth to velocity discontinuities and to modify techniques used to process and interpret these data. Recordings of teleseismic P-phases will be used to interpret P-to-S conversions for upper mantle discontinuities. Regional events will also be processes to determine the feasibility of augmenting the teleseismic information with interpretation of reflected energy from upper mantle discontinuities. The results will be used to design additional seismic experiments with the ultimate goal of producing a detailed map of the thickness of the transition zone (the interval between the 410 and 660 km discontinuities). Laboratory experiments using scale modeling of GPR reflections will be used to refine the interpretation techniques. The advanced understanding of interpretive work in the electrical and seismic techniques will be combined to improve the resolution of both methods. The PI will attend a short course on GPR methods to polish his skills in this technique, which is relatively new to him. GPR studies on physical models permit refinement of the interpretive methods. These refinements may then be used to improve interpretations of seismic data. At the same time, the PI has demonstrated the ability of the velocity spectrum stacking method to resolve thickness of a layer more accurately than absolute depth. This technique may be especially valuable for interpretation shallow reflection data where absolute depth my be well known from drilling. Anticipated products are a research proposal to create a much more refined map of the thickness of the transition zone, and an Instrumentation and Laboratory Improvement proposal for undergraduate instruction in field GPR techniques.
