Equatorial Pacific magnetic anomalies identified from vector aeromagnetic data

Abstract

SUMMARY It has long been challenging to identify magnetic anomalies due to seafloor spreading in the equatorial Pacific. Here we show that Project Magnet vector aeromagnetic profiles from the equatorial Pacific record magnetic anomalies due to seafloor spreading much more clearly than do shipboard total intensity profiles. The anomalies are reliably recorded at wavelengths between ≈20 and ≈150 km in the vertical and east components, which have high coherence, differ in phase by ≈90°, and resemble synthetic magnetic anomaly profiles. From an analysis of a single near‐equatorial vector aeromagnetic profile we infer that the magnetic lineations strike ≈8°–10° counter‐clockwise of north and that magnetic anomaly 7 is located ≈400 km further east than previously estimated. The newly estimated location of anomaly 6 is consistent with a tentative estimate by Wilson from a low‐amplitude shipboard magnetic profile. Because the skewness of profiles over the seafloor formed near the paleoequator changes rapidly with paleolatitude and paleostrike, a skewness analysis of these data may provide useful bounds on the location of Pacific Plate paleomagnetic poles, and indicate that this seafloor has had little, if any, northward motion relative to the spin axis since it formed.

Birth of an intraoceanic spreading center

“…1). Our interpretation is in good agreement with the fi ndings of Wilson (1996) and Horner-Johnson and Gordon (2003) in the northwestern corner of the region as well as ages inferred from Deep Sea Drilling Project drilling in the area (Hays et al, 1972), and represents a major revision of central Pacifi c magnetic anomaly identifi cations compared to global compilations of oceanic magnetic lineations (Cande et al, 1989). Seafl oor spreading anomalies between chrons 9 and 7 (28 Ma and 25 Ma, respectively) form straight lines striking N355°E over a distance of ~900 km between the Nicaragua fracture zone to the north and the Viru fracture zone to the south (Fig.…”

A new towed marine vector magnetometer: methods and results from a Central Pacific cruise

“…A number of analytical tools in both the time/space and frequency/wavenumber domains have been developed for fully oriented vector magnetometer data acquired in marine surveys with STCM (Isezaki 1992;Seama et al 1993;Korenaga 1995;Yamamoto & Seama 2004) and in aeromagnetic surveys (Parker & O'Brien 1997;Horner-Johnson & Gordon 2003). However, orientation control for towed marine systems is limited in yaw.…”

“…Parker & O'Brien (1997) and Horner-Johnson & Gordon (2003) describe various methods which were successfully applied to aeromagnetic vector data of Project Magnet. Parker & O'Brien (1997) and Horner-Johnson & Gordon (2003) describe various methods which were successfully applied to aeromagnetic vector data of Project Magnet.…”

“…In Section 3, we describe the processing from raw data to the anomaly reconstruction for the vector and gradiometer data. Finally, in Section 6 we apply wavenumber domain analysis (based on the work of Parker & O'Brien 1997;Horner-Johnson & Gordon 2003) to estimate magnetic lineation strike and to examine the quality of the vector data. 2-D modelling and interpretation follow in Section 4.…”

Misalignment calibration of geomagnetic vector measurement system using parallelepiped frame rotation method

“…Providing that the attitude information of three axis magnetometer is known, the magnetic field components on local geography coordinate can be known: north magnetic field, vertical magnetic field, east magnetic field [12][13][14][15]. One key factor influencing the measurement result of geomagnetic measurement system is the attitude measurement accuracy.…”