Interpretation of Gravity Anomalies Over an Inclined Fault of Finite Strike Length With Quadratic Density Function

The equation for the gravity anomaly of an inclined fault of finite strike length with quadratic density function is derived. The coefficients of the density function and the strike length are assumed to be known. Synthetic anomaly profiles of the fault model for the half strike lengths Y=2, 5, 10, 25, 50 and 100 km and for various values of dip and depths to top and bottom of the fault surface are calculated. Distances are measured from an arbitrary reference point, and the origin of the fault model, dip, and depths to top and bottom, are treated as unknown parameters. These parameters are solved by the Marquardt’s algorithm. The convergence of the method is shown by plotting the values of the objective function, the damping parameter lambda and the various parameters, with respect to iteration number. The same anomaly profiles are interpreted for different initial models. The method converges for all cases. A field profile across the Weardale granite, in northeast England, is interpreted as two faults by the present method.