Assessing the dependence of seafloor displacement measurements from repeated sidescan sonar surveys upon ship speed and track separation

Accurate seafloor geodetic methods are critical to the study of marine natural hazards such as megathrust earthquakes, landslides, and volcanoes. Digital image correlation of repeated sidescan sonar surveys has been demonstrated as a technique for measuring seafloor displacement that is both economical and capable of obtaining measurements accurate to the meter scale regardless of seafloor depth. However, the optimal cruise parameters with which to collect such data remain unknown. We present repeated sidescan sonar surveys collected during the 2016 RR1605 cruise above the Ayu Trough, 200 nautical miles south of Palau. Unlike previous studies in which sidescan data were collected at slow ship speeds (<4 knots) and small track separation (<5 m), the RR1605 surveys were collected at moderate ship speeds (4-8 knots) and variable track separation (2-300 m). We perform digital image correlation on these surveys to assess the sufficient cruise parameters required to obtain displacement measurements on the meter scale.