Gravity Data Inversion by a Faulted 2-D Horizontal Block of Arbitrary Thickness With Application to Crustal Imaging

An efficient inversion scheme has been developed for the interpretation of a residual gravity profile measured over a 2-D truncated fault. The scheme determines the characteristic parameters (depth to the top surface of the fault, depth to the bottom surface of the fault, amount and direction of dip of the fault plane, and density contrast) and solves for the inverse characteristic parameters of a model in the space of their logarithms instead of the space of the model parameters themselves. The accuracy and convergence of the scheme have been successfully verified and assessed on various noise-free numerical examples. It was then carefully assessed on noisy numerical data, and it was found stable but nonunique. The sensitivity analysis and the numerical inversions have shown that the parameter that can be determined with the greatest accuracy is the amount of dip of the fault plane; the parameter is crucial for determining the fault type. The validity of the technique for practical applications has been successfully illustrated in two field examples for crustal imaging. The inversion of the Garber structure, Garber County, OK, USA, has revealed more accurate and realistic results than previously published interpretations. The data inversion of the Saganash Lake fault, Canada, indicates that the fault plane dips to the Southeast and the fault is of a reverse nature; this finding agrees well with the conclusion established by Nitescu and Halls (2002). The scheme is shown to be applicable for shallow and deep Earth imaging, and has potential applications in integrated and reconnaissance studies.