Showing papers by "Milo M. Backus published in 2007"

OBC Sensor Response and Calibrated Reflectivity

Abstract: Summary Given deep-water OBC data, we can combine hydrophone (P) and vertical-geophone (Z) data to separate upgoing and downgoing acoustic wavefields. By using the downgoing wavefield to estimate the seismic wavelet, we can recover compressional-wave reflectivity and provide an acoustic impedance log for the near-seafloor sedimentary section. This procedure requires the calibration of geophone response to hydrophone response with an appropriate matching filter (z2p). P and Z data containing only upgoing energy can be provided in several ways to estimate z2p and p2z filters. Alternatively, the multiple/primary ratio (in the frequency domain) can be used to obtain calibrated reflectivity from the hydrophone alone or from the geophone alone, with no sensor calibration required. We apply these methods to a deep-water OBC line. We obtain consistent results by all of the methods. By combining low-frequency (5–70 Hz) z2p filters based on energy arriving before the direct arrival, with high-frequency (25–180 Hz) z2p filters based on near-offset reflection data, we can provide broadband (5–180 Hz) calibrated reflectivity and impedance of shallow seafloor sediments.