|Title||Seafloor geodesy from repeated sidescan sonar surveys|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||DeSanto J.B, Sandwell DT, Chadwell C.D|
|Journal||Journal of Geophysical Research-Solid Earth|
|Type of Article||Article|
|Keywords||deformation; digital image correlation; displacement; eruption; Juan de Fuca Ridge; multibeam sonar; ridge; seafloor geodesy; tohoku-oki earthquake; trench|
Accurate seafloor geodetic methods are critical to the study of marine natural hazards such as megathrust earthquakes, landslides, and volcanoes. We propose digital image correlation of repeated shipboard sidescan sonar surveys as a measurement of seafloor deformation. We test this method using multibeam surveys collected in two locales: 2500m deep lightly sedimented seafloor on the flank of a spreading ridge and 4300m deep heavily sedimented seafloor far from any plate boundary. Correlation of these surveys are able to recover synthetic displacements in the across-track (range) direction accurate to within 1m and in the along-track (azimuth) direction accurate to within 1-10m. We attribute these accuracies to the inherent resolution of sidescan data being better in the range dimension than the azimuth dimension. These measurements are primarily limited by the accuracy of the ship navigation. Dual-frequency GPS units are accurate to approximate to 10cm, but single-frequency GPS units drift on the order of 1m/h and are insufficient for geodetic application.
We measure simulated seafloor displacement using repeated sidescan sonar surveys. From a platform height of 3–4 km and a ship speed of 0.5–3.5 knots, we are able to measure displacements accurate to tens of meters in the along-track (azimuth) direction and meters in the across-track (range) direction, an improvement over the previous Fujiwara et al.  study of approximately 1 order of magnitude.