Abstract: An optimized Block inversion method is proposed in order to satisfy the high accuracy requirement of the aquifer boundary with Magnetic Resonance Sounding (MRS). The priori information is established from the derivative result of the Smooth inversion, which provides the smooth distribution of the water content. Based on the Tikhonov regularized inversion theory, the interactive scheme of Block inversion is deduced and solved. The Block inversion provides the exact boundary and water content of the aquifer. The introduction of priori information resolves the problems of instability and low reliability compared with traditional Block inversion. A series of synthetic models with one or more aquifers under different blocks, noise levels, depths and thicknesses are simulated. Results show that the accuracy of the aquifer boundary from the proposed Block inversion method is superior to Smooth inversion, and the anti-interference ability and stability are stronger. A field case study of the MRS measurement proves that the optimized Block inversion based on priori information satisfies the requirements of inversion accuracy and stability. The proposed the method could also provide more details for an aquifer with complex internal structure.

Key words: technology of instrument and meter, priori information, inversion, aquifer boundary, stability