Determine the initial model for solving 2D gravity anomaly inversion problem by normalized full gradient method

Nguyen Nhu Trung (1), (2) , Tran Van Kha (1) , Bui Van Nam (1), (2)

(1) Institute of Marine Geology and Geophysics, VAST, 18 Hoang Quoc Viet, Hanoi, Vietnam

(2) Graduate School of Science and Technology, VAST, 18 Hoang Quoc Viet, Hanoi, Vietnam

Email: nntrung@imgg.vast.vn

ABSTRACT

The most important issue of solving the geophysical inversion problem in general and gravity in particular is to build a highly reliable initial hypothetical model related to geological boundaries from the other data sources (seismic or geological data) and gravity anomaly data. In may cases, however, the other data sources are often very few, not enough to build a reliable initial model, but we have to rely heavily on gravity data. Some auxiliary analysis methods have been used to build the initial model such as Bott's method, Euler's convolutional method, energy spectrum method, derivative filtering methods to determine the depth of boundary faces or the position of the horizontal boundaries. In this article, we introduce a new interpretation process of the normalized full gradient (NFG) method in estimating the uper and lower boundaries of the field sources. The result supports usefully to construct an initial model for solving the 2D inverse gravity problem. The analysis method is tested on synthetic model and actual gravity data in the East Vietnam Sea. The results showed that the initial model given by NFG method has high reliability and quite accuracy.

KEY WORDS: Gravity Inversion, Normalized Full Gradient, East Vietnam Sea, Initial model