3D Focused Inversion of Near-bottom Magnetic Data from Autonomous Underwater Vehicle in Rough Seas

Abstract

The observation area of an autonomous underwater vehicle (AUV) often contains undulating terrain in which the shallow portions make a great contribution to near-bottom magnetic data. Magnetic information from varying terrain may be inadvertently removed when traditional topographic correction methods are used to reduce the effect of undulating terrain on inversion results. In this study, we introduce a terrain-weighting matrix into the focused inversion process to overcome this problem. To counteract the natural decay of the potential field, we used the focused inversion with a minimum support function to obtain focused results and depth-weighting function. We also used the interpolation-iteration method to mitigate the influence of the fluctuating observation surface on the inversion results. We verified the effectiveness of the proposed method by conducting model tests using near-bottom data measured along the Southwest Indian Ridge (SWIR) by the AUV, Qianlong II. We obtained the 3D magnetization structure of the oceanic core complex (OCC) area at the 28th segment along the SWIR and concluded that the OCC was primarily composed of gabbroic rock.