Smiths rule

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Smith's rule The formula by which the maximum possible depth of a body of unknown shape can be determined using gravity data. The body can have either a positive or negative density contrast with the surrounding rocks. The maximum depth, dmax, is given by: dmax = Agmax/(δg/δx), where δg/δx is the maximum horizontal gradient of the gravity anomaly, gmax is the value of the anomaly peak, and A varies between 0.86 for a three-dimensional body to 0.65 for an essentially two-dimensional body.