Modeling and inversion of 3-D gravity tensor field

The gravity data observations have been traditionally carried out in geophysical exploration by measuring the vertical component of the gravity field. Only recently, a new technique for tensor gravity field observation has been developed (Veryaskin, 2000; Jorgensen and Kisabeth,2000). Modern day instruments are capable of picking up the tensor components of the gravity field, and hence the need arises for applying inversion theory to interpret the tensor data so obtained. Portniaguine and Zhdanov (1999) developed a focusing method for 3-D gravity data inversion. It is based on implementation of a new focusing stabilizer for regularized inversion of gravity data. In the current research project the primary focus has been on the extension of this technique to invert the first derivatives of the different components of the gravity field which together constitute the gravity tensor. The developed method is illustrated by the inversion of the synthetic tensor gravity data.

Four models were considered : 1) A simple cubic body of dimensions 150mx150mx150m 2) Two cubic bodies each of dimensions 150mx150mx150m separated by a distance of 150m along y-direction. 3) An inclined dyke and 4) A faulted inclined dyke. It was noted that the components gzz shows a much better resolution than the simple gz component, while the other off-diagonal components are not so good.

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Figure 1: The slice of the original model of a single cubic body and the results of inversion for the different tensor components and gz.

Figure 2: The slice of the original model of two cubic bodies each of dimensions 150mx150mx150m and the results of inversion for gz and the tensor components gzz and gh.

Figure 3: The slice of the original model of an inclined dyke and the results of inversion for gz and the tensor components gzz and gh.

Figure 4: The slice of the original model of an inclined dyke and the results of inversion for gz and the tensor components gzz and gh.