Analysis of VSP Data from the Cajon Deep Borehole

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This project involves the analysis of Vertical Seismic Profiling (VSP) data collected during Phase II drilling at Cajon Pass (1800 meters - 3500 meters). Analysis of the Phase II data is expected to: 1) determine the seismic attenuation and shear wave polarization measurements to 3500 meters; 2) define the seismic impedance and spatial extent of the major fracture- interval that was drilled through during Phase II; 3) define crustal reflectivity to 6-10 km.; 4) establish the depth to basement of the (normal faulted?) sedimentary section south of the well; and 5) explore the structure associated with a large strike-slip fault within one half well depth of the hole to the south. The Cajon Pass drillhole provides one of the most comprehensively logged crystalline rock sections in which to investigate fundamental properties of seismic wave propagation in basement rock. VSP data connect crustal microfabric and microstructure information obtained from drilling core and wellbore geophysical logs to large volume, long wavelength, long travel path seismic crustal observations. By measuring in-situ seismic attenuation, reflectivity, and shear wave polarization at a level of detail unattainable with surface seismic receivers, VSP data permit a firmer understanding of these phenomena as observed in the wider domain of surface observations.