A method for determining a set of surface locations lying along a predetermined line of survey beneath which there is a relatively high probability of existing subsurface mineral bodies exhibiting relatively high density and relatively low magnetic susceptibility by selecting for membership in said set those surface locations lying in regions where a local minimum of magnetic field intensity substantially correlates to a local maximum of gravitational field intensity, those surface locations lying within regions of local topographic irregularity wherein the gravitational field intensity substantially directly correlates with the surface elevation, and those surface locations lying within regions wherein a steep gradient between a local maximum and an adjacent local minimum of the magnetic field intensities substantially directly correlates to a steep gradient between a local maximum and an adjacent local minimum of the gravitational field intensities.
A method for producing isostatically corrected gravity displays using available gravity data sets. The values of crustal density, density contrast between lower crust and mantle, and crustal thickness at sea level required for the Airy-Heiskanen equation are determined by analysis of the data set. Crustal density is determined by fractal analysis. Density contrast is determined by cross plotting Bouguer anomaly values versus elevation. Crustal thickness is determined by plotting power spectra of free-air gravity grids. The values are then used in the Airy-Heiskanen equation to provide the value of depth to crust-mantle boundary at each data point location in order to make accurate isostatic corrections and to produce accurate isostatically corrected displays.
In a magnetic cartography process and apparatus, measurements are performed by magnetic field sensors placed in "fish" moved in the area to be mapped. Gradients are determined on the basis of the difference between the measurements supplied by two sensors at the same time, this applying to any pair of sensors, and/or on the basis of the difference between the measurements supplied by the same sensor at two different times, this applying to any sensor, which leads to at least one map of gradients which is broken down into a map of regional field gradients and a map of local field gradients. On the basis of the local field gradients, a determination takes place of the geological field relative to the area, or the gradients of the field and then the local field, by adding the geological field to the regional field determined on the basis of its gradients by an inversion and direct calculation method.
A quantitative method of geologic structural analysis of digital terrain data is described for implementation on a computer. Assuming selected valley segments are controlled by the underlying geologic structure, topographic lows in the terrain data, defining valley bottoms, are detected, filtered and accumulated into a series line segments defining contiguous valleys. The line segments are then vectorized to produce vector segments, defining valley segments, which may be indicative of the underlying geologic structure. Coplanar analysis is performed on vector segment pairs to determine which vectors produce planes which represent underlying geologic structure. Point data such as fracture phenomena which can be related to fracture planes in 3-dimensional space can be analyzed to define common plane orientation and locations. The vectors, points, and planes are displayed in various formats for interpretation.
A system and method determines the probability of oil or mineral deposits. At least one data collection device collects elevation slope, magnetic and gravity data sets for a predetermined area of the earth's surface. A processor receives the elevation slope, magnetic and gravity data sets and applies the gravity and magnetic data sets in a transfer function to link the elevation slope data set to the likely presence of oil or mineral deposits.
