Vector sensor observations of the 2 + mode pattern on the New England Mud Patch at 57 Hz

Abstract

We present recordings made by an Intensity Vector Autonomous Recorder (IVAR) deployed on the seafloor during the Sediment Characterization Experiment (SCE17) conducted on the New England Mud Patch [40°28’ N, 70°35’ W] in March of 2017. IVAR continuously and coherently records four channels of acoustic data, three from a tri-axial accelerometer embedded in a neutrally buoyant sphere and one from an omnidirectional hydrophone positioned 10 cm above the centroid of the sphere 1.2 m above the seafloor. Here we focus on IVAR recordings of a 57 Hz continuous wave tone generated by a low-frequency acoustic source (J-15) that was towed at 30 m depth by the R/V Endeavor along transects roughly parallel and perpendicular to bathymetric contours. Over the entire tow track deep signal fades occur in 1000 m intervals, suspected to be caused interference between two modes trapped by the sediment basement. A signature in the vector data identifies an additional interference structure superimposed on this pattern (a 2 + ...