Theory of the Bouguer Anomaly

Abstract

Although the Bouguer anomaly is the form of the gravitational field most commonly utilized for the investigation of geologic problems on land, the true significance of the combined free‐air and Bouguer correction is frequently misunderstood by geologists, geophysical students, and many senior geophysicists with specializations in areas other than potential fields. This confusion arises from the established practice of describing the Bouguer anomaly as having been reduced to a common datum, suggesting that the reduced gravity values are those that would be observed if the measurements could be made on the datum plane (e.g., Dobrin, 1976, p. 417).

Possible Quaternary growth of a hidden anticline at the front of the Jura fold-and-thrust belt: geomorphological constraints from the Forêt de Chaux area, France

“…Figure 2A shows the total Bouguer anomaly computed with a mean crustal rock density of 2.3. It reflects the gravity variations due to density variations within the earth crust [e.g., Ervin, 1977]. The anomaly values are negative and comprised between -31 and -4 mgal, indicating a rather deep Moho.…”

Complete spherical Bouguer gravity anomalies over Australia

“…There are two conceptually different views of the Bouguer gravity anomaly (e.g., Li & Götze 2001;Hackney & Featherstone 2003;Vaníček et al 2004): (1) In geophysics (e.g., Ervin, 1977;Chapin, 1996), the Bouguer gravity anomaly is defined at the location of the gravity observation and the Bouguer reduction aims to model and remove all "non-geological effects". This also requires upward continuation of normal gravity from the surface of the reference ellipsoid to the location of the gravity observation via the free-air correction (or reduction).…”

“…The planar model, however, only provides a crude approximation of reality, which is not the case for a spherical model providing an approximation closer to reality (e.g., Karl 1971;Qureshi 1976;Ervin 1977;Chapin 1996;LaFehr 1998;Nowell 1999;Smith et al 2001;Vaníček et al 2001;2004). In analogy to the planar case, the simple spherical Bouguer gravity anomaly only considers the gravitational effect of a spherical Bouguer shell, and the complete spherical Bouguer gravity anomaly additionally considers the gravitational effect of the topography residual to the spherical shell (spherical terrain correction).…”

“…Central to both the geophysical and geodetic views is the requirement to algebraically consider the gravitational effects of the topographic masses. While the general definition of the Bouguer gravity anomaly (either geophysical or geodetic) does not contain any approximation, the gravitational effect of the topographic masses is frequently approximated, thus leading to different variants of the Bouguer gravity anomaly (e.g., Heiskanen & Moritz 1967;Ervin 1977;Chapin 1996;Vaníček et al 2001;2004).…”

“…The Bouguer gravity anomaly is frequently used in geophysics to infer geological information from observed gravity (e.g., Ervin 1977;Chapin 1996) and in geodesy to provide boundary values on the geoid, which have been reduced by the gravitational attraction effect of all masses above the geoid (e.g., Heiskanen & Moritz 1967;Vaníček et al 2004). Central to both the geophysical and geodetic views is the requirement to algebraically consider the gravitational effects of the topographic masses.…”