In Situ Calibration for Geodetic Measurements on the Seafloor and in Oceanic Drill Holes
Date: 4/25/2019
Time: 09:30 AM
Room: Puget Sound
Geodetic observations in the oceans are challenging but important for understanding plate boundary processes. Precise pressure sensors can be used to detect changes in the elevation of the seafloor resulting from the rapid deflation of volcanoes and from slow-slip earthquakes in subduction zones. They can also be used to detect transient changes in volumetric strain in sealed boreholes. However, without a calibration method to remove sensor drift, they have limited sensitivity to long-term secular strain. Similarly, the horizontal channels of a sensitive accelerometer provide a means to measure changes in sensor tilt on the seafloor or in boreholes, but without a means to eliminate drift their sensitivity to long-term signals is also limited. We will describe ongoing efforts to assess in situ calibration techniques for pressure gauges and accelerometers that utilize resonant quartz crystal technology. The “A-0-A” calibration method for pressure sensors utilizes a valve to periodically switch the pressure measured by the sensor from the ambient external pressure to the internal pressure of the instrument housing for a calibration against the pressure measured by an accurate barometer. The “flipping” method calibrates tilt measurements on an accelerometer by periodically rotating the horizontal channels into the vertical orientation and measuring their drift relative to the acceleration of gravity which is assumed constant. We will present the results of an ongoing test of the A-0-A methods at 900 m depth on the MARS cabled observatory in Monterey Bay which shows that the drift corrections of two pressure sensors are consistent to ~1 mm/yr. A second test is planned for Axial Seamount where the A-0-A method can be directly compared to two alternative approaches to eliminate drift. Tests of the flipping tiltmeter are presently underway on Axial Seamount and at Piñon Flat Observatory and can be compared at each site to measurements obtained with other instruments.
Presenting Author: William S. D. Wilcock
Authors
William S D Wilcock wilcock@uw.edu University of Washington, Seattle, Washington, United States Presenting Author
Corresponding Author
|
Dana A Manalang manalang@uw.edu Applied Physics Laboratory, University of Washington, Seattle, Washington, United States |
Michael J Harrington mikeh@apl.washington.edu Applied Physics Laboratory, University of Washington, Seattle, Washington, United States |
Erik K Fredrickson erikfred@uw.edu University of Washington, Seattle, Washington, United States |
Geoff Cram cramg@apl.washington.edu Applied Physics Laboratory, University of Washington, Seattle, Washington, United States |
James Tilley jtilley@apl.washigton.edu Applied Physics Laboratory, University of Washington, Seattle, Washington, United States |
Justin Burnett jburnett@apl.washington.edu Applied Physics Laboratory, University of Washington, Seattle, Washington, United States |
Derek Martin dtmartin@apl.washington.edu Applied Physics Laboratory, University of Washington, Seattle, Washington, United States |
Taro Kobayashi taro@paroscientific.com Paroscientific, Inc., Redmond, Washington, United States |
Jerome M Paros paros@paroscientific.com Paroscientific, Inc., Redmond, Washington, United States |
In Situ Calibration for Geodetic Measurements on the Seafloor and in Oceanic Drill Holes
Category
Advances in Tectonic Geodesy