KM2401

KM2401

Here we request 4 days of ship time and additional 4 days of transit yo complete the multibeam coverage of the area of the Haxby Gravity Rolls. A brief report of the KM2401 follows. The objective of this study is to determine the origin of Haxby gravity lineaments, which are small, periodic undulations (150-250 km wavelength) in the gravity field. They are observed on the Pacific plate in areas with seafloor is devoid of large volcanoes and other topographic structures. We deployed 40 ocean bottom broadband magnetotelluric instruments to measure variations in mantle conductivity in the litho- sphere and asthenosphere, and mapped the seafloor topography and sonar backscatter, in a 130 km by 600 km area northeast of the Marquesas islands in the Pacific Ocean basin. By correlating the measured conductivity and bathymetry with the gravity anomalies, we will be able to distinguish between multiple competing models attempting to explain the Haxby lineaments. During the cruise we deployed 40 instruments. One failed to be recovered and 39 were recovered and had good data. We planned to map an area 600 by 200 km but only had time for 600 X 130 km because ship speed was curtailed due to a need to conserve fuel so the mapping time and, thus area covered, was reduced by 5.8 days. Nevertheless this combined MT/bathymetry data recovery is excellent. Other data collected include magnetic field during mapping and gravity during the entire cruise. In addition, multiple instruments on the ship recorded ocean surface temperature and other meteorological data.