HR: 15:10h
AN: GP53A-05 INVITED     [Abstracts]
TI: Monte Carlo Inversion of Gravity and Magnetic Data in 3D
AU: * Bosch, M
EM: boschm@ucv.ve
AF: Universidad Central de Venezuela, Laboratorio de Simulacion e Inversion Geofisica,
AB: Inference of earth medium structure and properties is based on multidisciplinary data and information. Commonly, geophysics, petrophysics and geology need to be integrated to produce a realistic description of earth structures, basins and reservoirs. To achieve a quantitative combination of such different types of information we use a statistical approach that begins with defining a common model jointly describing structural, petrophysical and physical properties of the medium. This prior statistical model represents the knowledge of the medium structure and properties before taking into account the information provided by the geophysical surveys. By inverting the geophysical data onto the common model, we further constraint the model to jointly explain the geophysical observations and comply with the petrophysical and geological information. The related calculations are developed using sampling (Monte Carlo) techniques. We follow this approach for the joint inversion of gravity and magnetic data to infer the 3D structure and properties of an earth volume. We model the major lithotype regions and the medium mass density and magnetic susceptibility fields. The three model properties (lithotype, density and susceptibility) are linked by conditioning the physical property statistics to the lithotype using petrophysical and geostatistical information. In this way the gravity and magnetic data are coupled to a common model structure. We generate a large number of model realizations that jointly honour the prior structural and geostatistical information, and the likelihoods with the gravity and magnetic observations, calculating final estimates and probabilities of the medium model parameters. We have applied the joint gravity and magnetic inversion approach to infer sedimentary basin and crustal structure in 3D, with interest to regional exploration of hydrocarbon resources. The statistical model in this case constraints the structure of the basin and the rock properties using information obtained from the geology, seismic surveys and rock sample measurements. With the method we obtain basement and Moho estimates and full description of their probabilities. In a different application we study the region of interaction between the South American and Caribbean plates to infer the lithospheric structure and the low angle subduction of the latter beneath South America.
DE: 0903 Computational methods: potential fields (1214)
DE: 0920 Gravity methods (1219)
DE: 0925 Magnetic and electrical methods (5109)
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 1295 Integrations of techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly