Magnetic Anomalies Caused by 3D Polyhedral Structures With Arbitrary Polynomial Magnetization. Issue 18 (21st September 2022)

• Record Type: Journal Article
• Authors: Ren, Zhengyong; Zhang, Yuanlei; Zhong, Yiyuan; Pan, Kejia; Wu, Qihong; Tang, Jingtian
• Is Part Of: Geophysical research letters. Volume 49:Issue 18(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-21
• Subjects: planet structure -- gas and oil resources -- unexploded ordnance -- mineral deposits -- magnetic exploration -- analytical solutions; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL099209
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Magnetization is a natural property of magnetic materials which is widely used to analyze paramagnetic data, locate unexploded ordnance, explore mineral deposits and gas resources, and image anomalous magnetic structures in the Earth's crust. An essential and challenging task is to compute accurate magnetic anomalies caused by realistic magnetic 3D structures. In this study, for the first time, we derive the analytical expressions of magnetic potential, magnetic field and magnetic gradient tensor for magnetic materials with 3D polyhedral shapes and magnetization vectors that may vary in the space following polynomial trends. The order of polynomials can vary from one to high positive integers in both horizontal and vertical directions. Synthetic and realistic deposit models are used to validate our analytical solutions. We release the open‐source code in C++. Plain Language Summary: The geophysical magnetic exploration method is widely applied in the exploration of mineral deposits and gas resources, studies of sea‐floor spreading, detection of military and civilian magnetic objects, and Earth crust and other planets imaging. To interpret anomalous magnetic data acquired by ground, airborne, borehole, marine, and satellite magnetic surveys, geophysicists need to accurately compute the magnetic field and magnetic gradient tensor field of 3D magnetic structures with realistic magnetization. In this study, we successfully derive a set of closed‐form solutions of magnetic field and magnetic gradient tensor for 3D polyhedral structures with magnetization vectors which may vary in the space according to polynomial laws of arbitrary order. The intensity of magnetization can also vary in both horizontal and vertical directions. Based on the fact that 3D polyhedral bodies can well approximate arbitrary geometries of realistic structures and polynomial magnetization variations can well represent arbitrary distributions of magnetization, our closed‐form solutions could accurately compute the magnetic field and magnetic gradient tensor caused by realistic geological rocks and would play an essential role in the magnetic exploration method. Key Points: Closed‐form solutions of magnetic field and magnetic gradient tensor are derived for 3D polyhedral structures with complicated magnetization The magnetization in polyhedrons can vary in both horizontal and vertical directions Open source C++ software is free to use