New Approaches to In Situ Calibration for Seafloor Geodetic Measurements

Seafloor geodesy is challenging but important for understanding the hazards from earthquakes and tsunamis along subduction zones. Two methods of seafloor geodesy are presented based on obtaining self-calibrated measurements with resonant quartz crystal technology sensors. The A-0-A method for calibrating pressure observations utilizes the internal pressure of the instrument housing as a reference pressure to calibrate sensor drift. An 8-month seafloor test at a depth of 900 m, shows the method has reduced the relative drift between two pressure sensors to <1 mm. The rotating (or flipping) tiltmeter calibrates the accelerations of the horizontal channels of a tri-axial accelerometer by rotating them into the vertical where the acceleration of gravity is used as a reference acceleration. Laboratory tests are very promising and deployments are planned on the seafloor and at a geodetic observatory.