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TitleAPT: an instrument for monitoring seafloor acceleration, pressure, and temperature with large dynamic range and bandwidth
AuthorDavis, E E; Heesemann, M; Farrugia, J J; Johnson, G; Paros, J
SourceBulletin of the Seismological Society of America vol. 109, no. 1, 2019 p. 448-462,
Alt SeriesNatural Resources Canada, Contribution Series 20190034
PublisherSeismological Society of America (SSA)
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®)
ProvinceBritish Columbia; Western offshore region
NTS92C; 92E
AreaVancouver Island
Lat/Long WENS-132.0000 -125.0000 49.5000 47.0000
Subjectsmarine geology; tectonics; geophysics; in-field instrumentation; equipment testing; crustal movements; pressure; temperature; geodesy; geodynamics; oceanography; geophysical surveys; seismic surveys; seismology; microearthquakes; seismic waves; earthquakes; tides; tectonic evolution; deformation; gravity interpretations; Northeast Pacific Telemetred Undersea Networked Experiment (NEPTUNE); ground motion; ground acceleration; microseisms; infragravity waves
Illustrationsphotographs; schematic diagrams; location maps; tables; time series; spectra; plots
ProgramAssessing Earthquake Geohazards, Public Safety Geoscience
Released2019 01 15
AbstractA simple tool has been developed to facilitate the study of interrelated geodetic, geodynamic, seismic, and oceanographic phenomena in marine settings. It incorporates quartz pressure and triaxial acceleration sensors and a low-power, high-precision frequency counter. The sensors are housed in a 6-cm outside-diameter, 1-m-long pressure case that is pushed vertically into the seabed with a submersible or remotely operated vehicle, with no profile remaining above the seafloor to cause current-induced noise. The mass of the tool is designed to match that of the sediment it displaces to optimize coupling. Intrinsic measurement precision of the order of 1/100000000 of full scale (in this instance, a pressure range equivalent to 4000 m of water depth and an acceleration range of ±3g) allows observations of pressure, acceleration, and tilt variations of 0.4 Pa, 0:6 micrometres/s2, and 0:06 microrad, respectively. Temperature variations measured near the top and at the bottom of the instrument are resolved to better than 0.1 mK. With the large dynamic ranges, high sensitivities and broad bandwidth (10-Hz Nyquist to drift-limited zero-frequency DC), ground motion associated with microseisms, strong and weak seismic ground motion, tidal loading, and slow and rapid geodynamic deformation-all normally studied using disparate instruments -can be observed with this single tool. Examples of data are provided from four deployments with connections to the Ocean Networks Canada Northeast Pacific telemetered undersea networked experiment (NEPTUNE) observatory cable.
Summary(Plain Language Summary, not published)
A new tool has been developed that combines a recently developed tri-axial quartz accelerometer (Paroscientific/Quartz Seismic Sensors Inc.) and high precision (1 part per billion) frequency counting system developed initially for borehole observatories and now passed on for commercial manufacture. The tool, called APT, measures acceleration, temperature, and pressure, and is housed in a slim titanium pressure case that is pushed into the seabed by a submersible or remotely operated vehicle. Output is insensitive to the orientation of the instrument, and the sensors are robust to vibration. This robustness, its light weight and small volume, its low power consumption, and its linear response over an extremely broad frequency response make it ideal for many seafloor and borehole applications where both seismic and geodetic objectives can be realized. Several tools are already installed as part of the ONC Earthquake Early Warning system.