HR: 1340h
AN: GP23A-0026    [Abstracts]
TI: A Plea for Marine Vector Magnetometers: Cruise Experiences From the Central Pacific
AU: * Engels, M
EM: M.Engels@bgr.de
AF: BGR Federal Institute for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Barckhausen, U
EM: udo.barckhausen@bgr.de
AF: BGR Federal Institute for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Gee, J
EM: jsgee@ucsd.edu
AF: Scripps Institution for Oceanography, 9500 Gilman Drive, La Jolla, CA 92093 United States
AB: The research cruise SONNE-180 was carried out in the Central Pacific at about 120°W just south of the Equator. The research area on the Pacific plate is conjugated to the break-up of the Farallon plate into Cocos and Nazca plates 23 m.y. ago. This presentation is focusing on instrumental and methodological developments while the resulting plate tectonic reconstruction of the East Pacific is presented in a separate paper by Barckhausen. The Magnetometer array consisted of i) two Overhauser sensors (SeaSpy) recording the total magnetic field in gradiometer mode, ii) a newly developed marine vector magnetometer (BGR) which can be deployed on the same cable together with the two gradiometer sensors, and iii) a second, independent vector magnetometer system (SIO). Processed vector magnetometer yielded identical time series in the total magnetic field with the Overhauser sensors. Also the vertical component of both vector magnetometers is in a good agreement. Furthermore, applying the gradiometer mode to a Fluxgate-Overhauser pair of sensors worked as well as the standard Overhauser-Overhauser gradiometer. A new processing scheme has been applied to the data of all sensors containing a band pass filter in time domain in order to limit purely on wavelengths related to seafloor spreading anomalies. Those pre-processed total magnetic field data entered the anomaly reconstruction free of external temporal variations by summing up the gradiometer differences. Euler rotations by inclinometer angles provided the vertical component of the vector magnetometers. Furthermore, vector magnetometer data enabled processing in the spectral domain (multitaper method applied here). Fitting synthetic anomaly patterns to the observed data is much more straightforward for the vertical component than for the small total field anomalies of about half amplitude. Furthermore, synthetic models are better constrained because they have to predict simultaneously all components. In summary, marine vector magnetometers are an important step ahead in marine magnetics due to additional component information and increased possibilities in analysis and modelling, especially in regions where total field anomalies are small.
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 1550 Spatial variations attributed to seafloor spreading (3005)
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005