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

Abstract

In this paper, an inversion method based on the Marquardt's algorithm is presented to invert the gravity anomaly of the simple geometric shapes. The inversion outputs are the depth and radius parameters. We investigate three different shapes, i.e. the sphere, infinite horizontal cylinder and semi-infinite vertical cylinder for modeling. The proposed method is used for analyzing the gravity anomalies from assumed models with different initial parameters in all cases as the synthetic data are without noise and also corrupted with noise to evaluate the ability of the procedure. We also employ this approach for modeling the gravity anomaly due to a chromite deposit mass, situated east of Sabzevar, Iran. The lowest error between the theoretical anomaly and computed anomaly from inverted parameters, determine the shape of the causative mass. The inversion using different initial models for the theoretical gravity and also for real gravity data yields approximately consistent solutions. According to the interpreted parameters, the best shape that can imagine for the gravity anomaly source is the vertical cylinder with a depth to top of 7.4 m and a radius of 11.7 m.

Parameters estimation from the gravity anomaly caused by the two-dimensional horizontal thin sheet applying the global particle swarm algorithm

“…Gravity data interpretation is ill-posed and non-unique which is evident through various geometric-shapes of subsurface structures that can produce similar gravity anomaly at the surface of the earth. So, we minimize this non-uniqueness and ill-posedness by finding the desired geometry for subsurface targets with an identified density followed by the inversion process (Eshaghzadeh et al, 2019).…”