Gravity Anomalies of 2.5-D Multiple Prismatic Structures with Variable Density: A Marquardt Inversion

Abstract

We present an inversion technique based on the Marquardt algorithm to estimate the depth of a 2.5-D sedimentary basin in addition to the regional gravity anomaly that is associated with the residual gravity anomaly, wherein the density contrast varies parabolically with depth. Forward modeling is carried out through a derived analytical gravity expression of a 2.5-D vertical prism. Inversion of a theoretical gravity anomaly with and without a regional gravity anomaly illustrates the procedure that it is found to be insensitive to the regional gravity effect. Furthermore, the algorithm is exemplified with the gravity anomalies of the derived density-depth model of the Godavari subbasin, India with a parabolic density profile resulting in a more consistent geological model rather than a constant density profile. The main advantage of this method is that it works well even when the profile of interpretation does not bisect the strike length of the sedimentary basin.

Marquardt inverse modeling of the residual gravity anomalies due to simple geometric structures: A case study of chromite deposit

“…N is the number of theoretical gravity data. We have employed the Marquardt's algorithm (Marquardt, 1963) given by Chakravarthi and Sundararajan (2006) for minimizing the misfit function until the normal equations can be solved for over all modifications of the two unknowns structural parameters (depth and radius), as:…”

“…In this paper, a simultaneous non-linear inversion based on Marquardt optimization is developed to estimate the radius and depth parameters of the simple structures such as sphere, infinite horizontal cylinder and semiinfinite vertical cylinder. The Marquardt inversion method has been used for modeling the geological structures such as faulted beds (Chakravarthi and Sundararajan, 2005), anticlinal and synclinal structures Sundararajan, 2007, 2008), multiple prismatic structures (Chakravarthi and Sundararajan, 2006). The validity of the method is tested on synthetic gravity data with and without random noise and also on a real gravity data set from Iran.…”

Application of Cauchy-type integrals in developing effective methods for depth-to-basement inversion of gravity and gravity gradiometry data

“…The northern part (the Deadman Lake and Surprise Spring basins) and the southern part (Joshua Tree basin) of the survey area will be inverted separately. To speed up the inversion and get the most reasonable result, the well-known Bouguer slab formula (Chakravarthi and Sundararajan, 2006) could be applied to generate an initial model:…”

Regularization parameter selection in the 3D gravity inversion of the basement relief using GCV: A parallel approach

“…Following Chakravarthi and Sundararajan (2006), the nonlinear inverse problem for the estimation of the basement relief from the gravimetric data is posed as a problem of minimization of an objective function or error function as follows: − ) that are the parameters to be estimated. The diagram on the right shows the j-th prism and the anomalous gravitational field at the k-th observation point produced by all prisms.…”