Abstract
We calibrate a technique to use repeated multibeam sidescan surveys in the deep ocean to recover seafloor displacements greater than a few meters. Displacement measurements from seafloor patches (3 km by 20 km) on the port and starboard side of the ship are used to estimate vertical and across-track displacement. We present displacement measurements from a survey of the Ayu Trough southwest of the Marianas Trench using a 12 kHz multibeam. Vertical and across-track displacement errors for the 12 kHz multibeam sonar are typically 0–2 m with RMS uncertainties of 0.25–0.67 m in the across-track and 0.37–0.75 m in the vertical as determined by 3-way closure tests. The uncertainty of the range-averaged sound velocity is a major error source. We estimate that variations in the sound velocity profile, as quantified using expendable bathythermographs (XBTs) during data collection, contribute up to 0.3 m RMS uncertainty in the across-track direction and 1.6 m RMS uncertainty in the vertical direction.
Acknowledgments
This paper is derived from work published in the dissertation DeSanto (Citation2018). We would like to thank the Scripps Ship Scheduling Office, Shipboard Technical Services, James Holmes, Captain Dave Murline, and the crew of the R/V Roger Revelle, without any of whom the RR1605 cruise would not have been possible.