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Title: Three-dimensional gravity modeling and focusing inversion using rectangular meshes.

Three-dimensional gravity modeling and focusing inversion using rectangular meshes. Rectangular grid cells are commonly used for the geophysical modeling of gravity anomalies, owing to their flexibility in constructing complex models. The straightforward handling of cubic cells in gravity inversion algorithms allows for a flexible imposition of model regularization constraints, which are generally essential in the inversion of static potential field data. The first part of this paper provides a review of commonly used expressions for calculating the gravity of a right polygonal prism, both for gravity and gradiometry, where the formulas of Plouff and Forsberg are adapted. The formulas can be cast into general forms practical for implementation. In the second part, a weighting scheme for resolution enhancement at depth is presented. Modelling the earth using highly digitized meshes, depth weighting schemes are typically applied to the model objective functional, subject to minimizing the data misfit. The scheme proposed here involves a non-linear conjugate gradient inversion scheme with a weighting function applied to the non-linear conjugate gradient scheme's gradient vector of the objective functional. The low depth resolution due to the quick decay of the gravity kernel functions is counteracted by suppressing the search directions in the parameter space that would lead to near-surface concentrations of gravity anomalies. Further, more » a density parameter transformation function enabling the imposition of lower and upper bounding constraints is employed. Using synthetic data from models of varying complexity and a field data set, it is demonstrated that, given an adequate depth weighting function, the gravity inversion in the transform space can recover geologically meaningful models requiring a minimum of prior information and user interaction. « less
Authors:
Publication Date:
OSTI Identifier:1048262
Report Number(s):LBNL-4906E
Journal ID: ISSN 0016-8025; GPPRAR; TRN: US201216%%844
DOE Contract Number:DE-AC02-05CH11231
Resource Type:Journal Article
Data Type:
Resource Relation:Journal Name: Geophysical Prospecting; Journal Volume: 59; Journal Issue: 5; Related Information: Journal Publication Date: 2011
Research Org:Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:Earth Sciences Division
Country of Publication:United States
Language:English
Subject: 54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; ALGORITHMS; DECAY; FLEXIBILITY; FOCUSING; IMPLEMENTATION; KERNELS; RESOLUTION; SIMULATION; TRANSFORMATIONS; VECTORS; WEIGHTING FUNCTIONS