Estimation of Fault Parameters in Southwest of the Thrace Basin from Gravity Gradient Data

Abstract

Characterization of fault zones plays an important role for earthquake studies, geothermal and mineral resource exploration. This problem can be achieved by optimizing parameters of a defined synthetic model iteratively using gravity, gravity gradients or magnetic data. Curvature gradients indicate deviations of an equipotential surface from a spherical surface, therefore, reflecting deviations of mass distributions from a source point. In this study, differential curvature gradient is used as it identifies linear structures such as dip-slip faults and geological contacts. Curvature gradients are computed from gravity gradient observations which are derived from the high-resolution Earth Gravitational Model 2008. Estimating the fault parameters from gravity gradients is a complex nonlinear geophysical inverse problem that requires finding the minimum of a multi-variable cost function. A global optimization technique called simulated annealing (SA) is used to estimate location, dip angle and some depth parameters of the faults located in southwest side of the Thrace basin in Türkiye. In the optimization technique, a straight solution is inevitably applied to calculate the theoretical anomaly to be compared with the observed anomaly in each search step. In this case, the problem requires constructing a mathematical or geophysical interpretation model. Such a model is designed as a dip-slip fault model. The results show that dip angle estimates indicate high-angle faults which are found to be consistent with the seismic studies.