Comparison of a Few Ocean Bottom Node Designs and the Fidelity of the Data They Record

Vector fidelity is the ability of a given sensor to record the motion of the seabed as if the sensor was not there. Hence, vector infidelity may come from either poor coupling or from an influence of the sensor package on the seabed around it. To study the implications of ocean bottom node design on coupling and vector fidelity, we analyse data from a field experiment in which several types of nodes have been deployed at close proximity. The data provide a good opportunity to compare the effect of the shape and design of a node on the quality of the data it provides. We have data from nodes with internal and with external sensors, from nodes which are planted, from nodes that are gravitationally coupled, and from nodes with different contact area, and height of centre of inertia. We find variations in the data that are consistent with the node design. We analyse the amount and the form of shear-wave induced noise on the vertical component and of P-wave induced noise on the horizontal components.