Abstract
Full tensor magnetic gradient measurements are available nowadays. These are essential for determining magnetization parameters in deep layers. Using full or partial tensor magnetic gradient measurements to determine the subsurface properties, e.g., magnetic susceptibility, is an inverse problem. Inversion using total magnetic intensity data is a traditional way. Because of difficulty in obtaining the practical full tensor magnetic gradient data, the corresponding inversion results are not so widely reported. With the development of superconducting quantum interference devices (SQUIDs), we can acquire the full tensor magnetic gradient data through field measurements. In this paper, we study the inverse problem of retrieving magnetic susceptibility with the field data using our designed low-temperature SQUIDs. The solving methodology based on sparse regularization and an alternating directions method of multipliers is established. Numerical and field data experiments are performed to show the feasibility of our algorithm.
Highlights
Using magnetic measurements for geophysical exploration is a widely chosen technique
Our new contributions are: (1) In data acquisition, we have designed a low-temperature superconducting quantum interference devices (SQUIDs) system, which is used to measure 9 components of the full tensor magnetic gradient field, and we have carried out successful airborne field work in 2016; (2) in solving methodology, the more suitable method (L1-norm regularization) which performs better for resource exploration compared with the conventional smooth inversion method is considered, and a weighted alternating direction method of multipliers is developed to solve the minimization problem; (3) this is the first time magnetic inversion results are reported using our new data with our device; it indicates from synthetic and field data tests that the inversion using full tensor magnetic gradient data can reveal much more valuable information than the traditional total magnetic intensity (TMI) data
Using full tensor magnetic gradient data measured by our self-designed low-temperature SQUID system to invert the magnetic parameter is first reported in the literature
Summary
Using magnetic measurements for geophysical exploration is a widely chosen technique. Our new contributions are: (1) In data acquisition, we have designed a low-temperature SQUID system, which is used to measure 9 components of the full tensor magnetic gradient field, and we have carried out successful airborne field work in 2016; (2) in solving methodology, the more suitable method (L1-norm regularization) which performs better for resource exploration compared with the conventional smooth inversion method is considered, and a weighted alternating direction method of multipliers is developed to solve the minimization problem; (3) this is the first time magnetic inversion results are reported using our new data with our device; it indicates from synthetic and field data tests that the inversion using full tensor magnetic gradient data can reveal much more valuable information than the traditional TMI data. Our device may be a proper choice for interested people for potential applications
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