The Bouguer Gravity Anomaly Map of the United States

Abstract

The U. S. Geological Survey has just announced the publication of the Bouguer Gravity Anomaly Map of the United States. This map, fourteen years in the making was prepared by the writer as Chairman of the AGU Special Committee for the Geophysical and Geological Study of the Continents. The active cooperation of many individuals and groups throughout the country was essential since the number of gravity observations, running into hundreds of thousands of measurements distributed on an eight‐ to fifteen‐mile spacing over much of the country, represents an undertaking beyond the capacity of a single individual or group. The five major sources of data were oil companies, government agencies, private exploration companies, mining companies, and universities. As much of the data was of a proprietary nature, the sponsorship of the AGU was a critical factor in obtaining it from company sources, since management policy does not favor the release of information that has cost the company large sums of money, especially to an individual. Similarly, the role of the AGU cannot be overemphasized in obtaining the active cooperation of government agencies and universities in releasing data prior to publication.

Satellite and surface geophysical expression of anomalous crustal structure in Kentucky and Tennessee

“…Regional gravity maps such as [4] show a prominent high in central Kentucky, elongated nearly north-south and extending into Tennessee. The anomaly is roughly 200 km long, 70 km wide, and has a relief of up to 70 mgal.…”

The Giles County, Virginia, seismic zone– Seismological results and geological interpretations

“…A steep gravity gradient runs the length of the Appalachians, with Bouguer gravity values rising eastward across the gradient as much as 80 mGal (Woollard and Joesting, 1964;Earth Physics Branch, 1974;Haworth and others, 1980). Figure 18 shows the part of the gradient in the region of interest here, near Giles County.…”

Geohydrology and ground-water availability in western Marshall and eastern Morgan counties, Alabama

“…Although certain procedural changes in the survey such as a random visiting pattern and incorporation of multiple readings at several stations within the grid would improve the reliability of such surveys considerably and allow more definitive statements concerning meter resolution, it is still apparent that additional resolution is required. The range of corrected readings obtained was about 500 microgals, a value which is very large in a relative sense, and cannot be reasonably attributed to regional gradients (Woodward and Joestring, 1964) or underground cavities. For instance, assuming a cavity at a depth of 75 feet, a radius of 15 feet, and a density contrast of 2.0, the following formula may be used to calculate a theoretical anomaly of about 10 microgals for a cavity similar to the one penetrated in well 0-2. war* where :…”