Depth Estimation of Potential Field Sources by Using Improved Chebyshev‐Padé Downward Continuation in Wave Number Domain

Abstract Studies of downward continuation mainly focused on improving the stability more than depth calculation. Stable downward continuation is a promising technique for estimating the depth of sources. In this study, based on the filter curve in wave number domain, a new depth estimation method was developed using the Chebyshev‐Padé downward continuation method. First, the filter curves of Tikhonov regularized method and the Chebyshev‐Padé downward continuation method in wave number domain were compared. We concluded the reason that the Tikhonov regularized method can be used to obtain the depth information is that the filter curve converges to zero. Therefore, to use the Chebyshev‐Padé downward continuation method for calculating the depth, a simple low‐pass filter based on upward continuation was used to improve it in the wave number domain, making the filter curve of the new improved method converge to zero. Similar to the Tikhonov regularized method, our new method can obtain the depth information when calculating downward continuation data from the original level to an expected maximum depth level. To verify the effectivity, different synthetic models were used to test our method, indicating that the new method can achieve a more reasonable depth compared to the Tikhonov regularized method. Finally, the new method was applied to real magnetic data collected using unmanned aerial vehicle aeromagnetic surveys to test on a big car in Southeastern Zhejiang, China. The calculated depth matches with its actual depth. These results show that the new method is a useful depth estimation tool for potential field sources.