Launching the SeaSpy gradiometer system during a recent cruise on the R/V Revelle.

Several fundamental tectonic problems of the equatorial Pacific remain unsolved due to the lack of magnetic anomaly data. A basic limitation encountered with the use of the standard proton precession magnetometer (or any total field instrument) is that total field anomalies over approximately north-south striking bodies are very small at low magnetic latitudes. Another problem encountered with magnetic surveys near the magnetic equator are the diurnal variations associated with the external field. The combined effects of these large diurnal variations and the low amplitude total field anomalies have severely limited the study of crustal anomalies on the equatorial East Pacific Rise (EPR). We have been using two new survey methods to overcome these problems: a total field magnetic gradiometer that allows removal of external field variations and a vector magnetometer. This latter sensor has the advantage that the vector components of the anomalous field are always greater than (or equal to) the total field anomalies and that the vector components can be used to assess the two dimensionality of the magnetic source.



Results from a test deployment of a new towed vector magnetometer system. Top two plots compare the total field anomaly data collected by a proton precession magnetometer (PPM) and the vector magnetometer (MRU6). Bottom plots show comparison of vector components (Hx = along track and Hz = vertical) from previous aeromagnetic survey and from the MRU6.

Related references:

Gee, J.S. and S.C. Cande, 2002, A surface-towed vector magnetometer, Geophys. Res. Lett., vol. 29, 10.1029/2002GL015245 (4 pages).

Recent and ongoing research projects:

1. A paleointensity record from the ocean crust
2. Mapping sea surface magnetic anomalies
3. Characterizing the time-averaged magnetic field
4. Long term variations in geomagnetic intensity
5. Magnetization of meteorites and lunar samples
6. Applications of magnetic data to fabric development in cumulates