Meter-Scale Seafloor Geodetic Measurements Obtained from Repeated Multibeam Sidescan Surveys

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.

Keywords:

• Multibeam sonar
• Seafloor positioning
• Seafloor sonar image

Acknowledgments

This paper is derived from work published in the dissertation DeSanto (2018). 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.

Additional information

Funding

This work was supported by the National Science Foundation, Marine Geology and Geophysics Division, grant 1536386. The RR1605 cruise was supported by the UC Student Ship Funds Program.