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Data Series 135: Iowa Complete Bouguer Gravity Anomaly Map

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Northeast Illumination

The colors on this Bouguer gravity anomaly (Hill and others, 1995) map represent gravity variations resulting from lateral density variations in the Earth. Positive anomalies (red colors) occur in areas with average density greater than the Bouguer reduction density of 2.67 gm/cc, whereas negative anomalies (blue colors) occur in areas of lower density.

The complete-Bouguer gravity anomaly grid was generated from 18,111 gravity station measurements in and adjacent to the State of Iowa. The source of the station information is the gravity data repository of the University of Texas-El Paso (UTEP) / PACES research center. Observed gravity measurements relative to the International Gravity Standardization Net 1971 (IGSN71) datum were reduced to the Bouguer anomaly using the 1967 gravity formula (Cordell and others, 1982) and a reduction density of 2.67 gm/cc. Terrain corrections were calculated radially outward from each station to a distance of 167 km (103.8 mi) using a method developed by Plouff (1977). The data were converted to a 2-km (1.24-mi) grid using minimum curvature techniques. This compilation does not include any unpublished data.

The grid for the Bouguer color-contour map is available from the data directory as grvcba.grd

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