Magnetization structure of Aogashima Island using vector magnetic anomalies obtained by a helicopter-borne magnetometer

서지정보

· 발행기관 : 한국지구물리.물리탐사학회
· 수록지 정보 : 지구물리와 물리탐사 / 12권 / 1호 / 17 ~ 26페이지
· 저자명 : Nobuhiro Isezaski, Jun Matsuo

초록

On Aogashima Island, a volcanic island located in the southernmost part of the Izu Seven Islands Chain, vector
magnetic anomalies were obtained in a helicopter-borne magnetic survey. The purpose of this study was to understand the
volcanic structure of Aogashima Island in order to mitigate future disasters.
Commonly, to obtain the magnetic structure of a volcanic island, total intensity anomalies (TIA) have been used, even
though they have intrinsic errors that have not been evaluated correctly.
Because the total intensity magnetic anomaly (TIA) is not a physical value, it does not satisfy Maxwell’s Equations,
Laplace’s Equation, etc., and so TIA is not suitable for any physical analyses. In addition, it has been conventionally assumed
that TIA is the same as the projected total intensity anomaly vector (PTA) for analyses of TIA. However, the effect of the
intrinsic error (eT = TIA–PTA) on the analysis results has not been taken into account. To avoid such an effect, vector magnetic
anomalies were measured so that a reliable analysis of Aogashima Island magnetization could be carried out.
In this study,weevaluated the error in TIA and used vector anomalies to avoid this erroneous effect, in the process obtaining
reliable analysis results for 3D, vector magnetization distributions. An area of less than 1 A/m magnetization was found in the
south-west part of Aogashima Island at the depth of 1–2 km. Taking the location of fumarolic activity into consideration, the
lower-magnetization area was expected to be the source of that fumarolic activity of Aogashima Island.

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