Polarisation Analysis of Ocean Bottom 3C Sensor Data

Bjorn Olofsson* and Christophe Massacand
CGGVeritas, Norway
*[email protected]

In this study we analysed vector fidelity of direct P and reflected P-S arrivals from multi-component ocean-bottom (OB) data, by mapping apparent polarisation as a function of azimuth and angle of incidence at the seabed. This demonstrates vector fidelity of seabed sensors at its root, i.e. as the amount of distortion of the incoming wave’s polarisation. We compared data from a cable system with data from nodes, as well as buried and unburied cable sensors. As expected, nodes show overall best vector fidelity. For OB cable data, on the other hand, buried sensors showed significantly better vector fidelity than unburied sensors, both for downgoing direct P-waves and upgoing P-S reflected waves. While both buried and unburied cable sensors exhibit vector infidelity to some degree in the direction along the cable, unburied sensors show in addition poor fidelity in the crossline direction. Vector infidelity of the unburied sensors may be misinterpreted as azimuthal anisotropy with a symmetry axis parallel to the cable.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain