A white cylindrical instrument with a thick clear lid. A black cylindrical element is fastened to the center of the lid. The instrument is filled with a clear fluid (dimethylpolysiloxane, silicone oil). Within the instrument is a smaller metal enclosure containing the strain gauge transducermechanism.
Accession Number: 2024.ph.878
Alternative Name: DPG
Primary Materials: Plastic, Silicone Oil
Information engraved in the metal faceplate underneath the clear lid includes the following: “DPG V6.3// SN 05043”
Dimensions (cm): Height = 25.5; Max Diam. = 15.
Placed on the seafloor, this instrument measures very low frequency pressure fluctuations from sources such as long surface gravity waves, tsunami, and microseisms. The working mechanism consists of a strain gauge transducer of single crystal silicon that measures the difference in pressure between the ocean pressure and the fluid in a reference reference chamber.
This artifact is in excellent cosmetic condition and appears to be intact. There is some corrosion on the metal threaded inserts embedded in the clear top window.
Associated Instruments:
Scripps Institution of Oceanography, Marine EM Laboratory. University of California, San Diego, USA.
Date of Manufacture: Late 20th c.
This instrument was used in seafloor compliance studies, that were conducted in 1997 and 1998 in the Cascadia continental margin. This was part of a four-year hydrate evaluation study that characterized hydrate deposits in the seafloor. (See Willoughby and Edwards 2000.)
This artifact is part of a small collection gathered from the office of Prof. Nigel Edwards of the University of Toronto Department of Physics in March of 2022.
Charles Cox, Thomas Deaton, and Spahr Webb (1984). “A Deep-Sea Differential Pressure Gauge.” Journal of Atmospheric and Oceanic Technology” Vol. 1, No. 3, 237–246.
E. C. Willoughby and R. N. Edwards (2000). “Shear Velocities in Cascadia from Seafloor Compliance Measurements.” Geophysical Research Letters 27, no. 7 (2000): 1021–24.
Scripps Institution of Oceanography, Marine EM Laboratory. Instruments | Deep-Sea Differential Pressure Gauges (DPGs). (Webpage archived February 17, 2024.)
The development of this instrument was funded by the U.S. Office of Naval Research (Cox, Deaton, and Webb 1984.) It likely emerged from research carried out by the U.S. Office of Naval Research and researchers at the Scripps Institution of Oceanography into the detection of submarines using very low frequency (VLF) acoustic sensors.
This example was used in seafloor compliance studies aimed at detecting and measuring hydrate formations. It was used with a self-leveling gravimeter (a modified Scintrex
CG-3), that measured vertical displacement. Compliance is defined as “the frequency-dependent transfer function between pressure and deformation.” Long period infragravity waves in the ocean’s surface are produced by non-linear interactions between wind-driven surface waves. The deformation produced by these waves can be used to analyze the subsurface properties of the seafloor (Willoughby and Edwards 2000.)