Publications

Export 4 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M [N] O P Q R S T U V W X Y Z   [Show ALL]
N
Ander, ME, Zumberge MA, Lautzenhiser T, Parker RL, Aiken CLV, Gorman MR, Nieto MM, Ferguson JF, McMechan GA.  1989.  A New Field Experiment in the Greenland Ice Cap to Test Newton Inverse Square Law. Annals of the New York Academy of Sciences. 571:672-680.   10.1111/j.1749-6632.1989.tb50553.x   AbstractWebsite

Recent experimental evidence suggests that Newton’s law of gravity may not be precise. There are modern theories of quantum gravity that, in their attempts to unify gravity with other forces of nature, predict non-Newtonian gravitational forces that could have ranges on the order of 102-105 m. If they exist, these forces would be apparent as violations of Newton’s inverse square law. A geophysical experiment was carried out to search for possible finite-range, non-Newtonian gravity over depths of 213-1673 m in the glacial ice of the Greenland ice cap. The principal reason for this choice of experimental site is that a hole drilled through the ice cap already existed and the uniformity of the ice eliminates one of the major sources of uncertainty arising in the first of earlier namely, the heterogeneity of the rocks through which a mine shaft or drill hole passes. Our observations were made in the summer of 1987 at Dye 3, Greenland, in the 2033-m-deep borehole, which reached the basement rock.

Parker, PR, Zumberge MA, Parker RL.  1995.  A New Method for Fringe-Signal Processing in Absolute Gravity Meters. Manuscripta Geodaetica. 20:173-181. AbstractWebsite

In all modern absolute gravity meters, an interferometer illuminated with a stabilized laser tracks the motion of a freely falling retroreflector. The value of gravity is measured by timing the passage of interference fringes. Typically, the sinusoidal fringe signal is converted to a series of pulses, a subset of which are input to a time digitizer. In our new system, the fringe signal is digitized with a fast analog-to-digital converter and fit to an increasing-frequency sine wave. In addition to being smaller and less expensive, the system should eliminate some potential systematic errors that may result from imperfect zero-crossing discrimination and pulse pre-scaling.

Zumberge, M, Faller JE, Rinker RL.  1984.  A new portable, absolute gravimeter. Precision Measurements and Fundamental Constants II. ( Taylor BN, Philips WD, Eds.).:405-409. Abstract
n/a
Sasagawa, GS, Crawford W, Eiken O, Nooner S, Stenvold T, Zumberge MA.  2003.  A new sea-floor gravimeter. Geophysics. 68:544-553.   10.1190/1.1567223   AbstractWebsite

A new reservoir management application uses precise time-lapse gravity measurements on the sea floor to detect seawater infiltration in offshore natural gas fields during production. Reservoir models for the North Sea Troll field predict gravity changes as large as 0.060 mGal within a 3-5-year period. We have constructed and deployed a new instrument-the ROVDOG (Remotely Operated Vehicle-deployed Deep-Ocean Gravimeter) system-for this application. Because the measurements must be relocated accurately (within 3 cm), we required a gravimeter which could be handled by an ROV and placed atop sea-floor bench marks. We have built an instrument based upon the Scintrex CG-3M land gravimeter. Motorized gimbals level the gravimeter sensor within a watertight pressure case. Precision quartz pressure gauges provide depth information. A shipboard operator remotely controls the instrument and monitors the data. The system error budget considers both instrumental and field measurement uncertainties. The instrument prototype was deployed in the North Sea during June 1998; 75 observations were made at 32 stations. The standard deviation of repeated gravity measurements was 0.026 mGal; the standard deviation of pressure-derived heights, for repeated measurements, was 1.4 cm. A refined instrument was deployed in August 2000 in a three-sensor configuration. Multiple sensors improved the precision by averaging more samples without incurring additional survey time. A total of 159 measurements were made at 68 station. The standard deviation of repeated measurements was 0.019 mGal; the standard deviation of pressure-derived heights was 0.78 cm. A ROVDOG pressure case rated to 4500 m depth has also been constructed. This system was deployed with the Alvin manned submersible in November 2000 to a depth of 2700 m.