Local separation of potential field anomalies using equivalent sources: application for the 3-D structure of mantle uplift beneath Von Kármán crater, the Moon

Abstract

SUMMARY The separation of regional-residual anomalies plays an important role in the processing of potential field anomalies for obtaining better understandings of the nature of the underground sources. Many methods have been developed to achieve the separation of anomalies that are of distinct wavelengths. On the other hand, fewer studies have addressed the separation of local anomalies from the observed potential field anomalies. In this paper, we introduce a new process for separating localized anomalies from the observations under the Cartesian and spherical coordinates. The separation is achieved using the equivalent source technique and an iterative inversion process which is to refine and finalize the separated local anomalies. Additionally, we introduce an inversion method for determining the equivalent sources that are of varying dimensions, as well as a quantitative measurement to assess the accuracy of the separation process. Verified with synthetic examples, the proposed method could extract arbitrary shaped local anomalies from the rest with low error levels. Subsequently, we apply the method to the construction of a 3-D model of the mantle uplift beneath the Von Kármán crater (VKC) on the Moon. The VKC is the landing site of the Chinese lunar exploration mission Chang'e 4, which lies in the northwestern portion of the South-Pole Aitken (SPA) basin on the far side of the Moon. Multiple generations of mare basalts are identified within the VKC, which indicates a complex geological history of the basin. Insights into the evolutionary history of this region can be obtained by investigating the deep crustal structure of the VKC using topographic and gravity data. Processed with the proposed method, the 3-D structure we obtain provides evidence for separated mantle uplifting events triggered by the two impact events that created the VKC and the Von Kármán M crater, respectively.