Data processing method and application of towed marine three-component magnetic gradiometer

doi:10.3969/j.issn.1001-909X.2024.02.008

Abstract

Abstract:

The towed marine three-component magnetic gradiometer can obtain the geomagnetic three-component and magnetic gradient data at the same time. Compared with the traditional towed geomagnetic total field magnetometer, the towed marine three-component magnetic gradiometer has the advantages of reducing the ship magnetic interference and resisting the influence of geomagnetic daily variation, but it also has some shortcomings such as sensitivity error, zero offset error, orthogonality error and position error. In the actual voyage, a section data measured by the towed marine three-component magnetic gradiometer was calibrated to the total geomagnetic field data measured by the G880 magnetometer, which proved its high stability and reliability. Based on the three component magnetic gradient data, the tensor invariants and the trend of magnetic boundary were obtained, and combined with the Euler deconvolution calculation, the magnetic source body on the measurement line was effectively identified and interpreted. The results show that the towed three-component marine gradiometer can effectively obtain the information of geomagnetic field, component and gradient, which can provide a more effective technical means for marine geomagnetic field measurement.

Key words: geomagnetic three components, calibration of scalar, magnetic gradient tensor, magnetic boundary trend map, Euler deconvolution

CLC Number:

P716.82

DANG Lingfeng, WU Zhaocai, DONG Chongzhi, ZHANG Jialing. Data processing method and application of towed marine three-component magnetic gradiometer[J]. Journal of Marine Sciences, 2024, 42(2): 81-90.

Figures/Tables 10

Fig.1 Flow chart of data acquisition

Fig.2 Sketch map of survey line location

Fig.3 Schematic diagram of axis rotation (The coordinate systems of the two magnetometers are O1X1Y1Z1 and O2X2Y2Z2, Based on the axes O1X1Y1Z1, the three rotation angles are α1,α2,α3. The dotted line is the virtual ideal orthogonal coordinate axis.)

Fig.4 Three-component magnetic induction intensity data of magnetometer T1 and T2

Fig.5 Three-component magnetic gradient data

Fig.6 Comparison of three-component composite geomagnetic total field with that measured by G880

Fig.7 The contrast diagram of magnetic gradient tensor (a), magnetic gradient tensor invariant (b) and total magnetic field gradient (c)

Fig.8 Comparison diagram of ISDV curve with magnetic inclination angle and magnetic declination angle of measured line

Fig.9 Strike diagram of magnetic boundary (The central point of the black line segment in the figure corresponds to the position of the magnetic boundary. The direction of the long line segment corresponds to the magnetic declination angle of the magnetic boundary, and the length of the line segment is proportional to the cosine value of the magnetic inclination angle of the magnetic boundary. The length of the short line segment is proportional to the standard deviation of the magnetic boundary vector.)

Fig.10 Comparison diagram of magnetic anomaly profile (a), topographic profile (b) and Euler inversion results (c)

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