Research > Endeavour Tomography Experiment
UPDATE COMING SHORTLY
The Endeavour Tomography experiment (ETOMO) is a collaborative experiment involving the University of Oregon (Doug Toomey and Emilie Hooft) and my group at the Univerity of Washington that is funded by the National Science Foundation as part of the Ridge2000 program. After two delays due to ship availability issues, the data acquisition was completed using the R/V Marcus G. Langseth on a cruise that extended for August 22 - September 19, 2009. Prior to the cruise, several radial Canadian environmental groups cynically tried to stop the experiment through lawsuits and misinformation but they only succeeded in delaying it by one day. You can read more about the environmental controversy here. This page focuses on the exciting science.
The goal of the tomography experiment is to test competing models regarding the controls on the segmentation and intensity of ridge crest processes and on the linkages between the distribution of hydrothermal vents and the properties of the thermal boundary layer that transports energy between the magmatic and hydrothermal systems. The recent discovery of an axial magma chamber (AMC) reflector beneath the central portion of the Endeavour segment of the Juan de Fuca ridge, as well as systematic along axis changes in seafloor depth, ridge crest morphology and hydrothermal venting provide an ideal target for testing conflicting hypotheses. The seismic experiment was designed to investigate the 3-D structure of the crust and uppermost mantle beneath the Endeavour segment, a RIDGE2000 Integrated Study Site (ISS).
|Configuration of the 3-D seismic tomography experiment showing ocean bottom seismometers from the Ocean Bottom Seismometer Instrument Pool (red and blue circles indicating WHOI and SIO instruments, respectively), airgun lines (faint black lines), vent fields (green stars) and the footprint of the axial magma chamber (bold black lines). (Full Sized Version)|
The experiment design is shown above and comprised 64 ocean bottom seismometers from the US Ocean Bottom Seismometer Instument Pool each with three orthogonal seismometers and a hydrophone and approximately 2000 km of airgun profiles obtained with the R/V Langseth's 6600 cubic inch 36 airgun array towed at depths of 9 m and 15 m. Operationally the experiment was a remarkable success. All 64 OBSs were recovered with data and there was sufficient time to reshoot the outer lines. The data collected will allow us to image four targets: (1) crustal thickness variations within 25 km of the axial high (0 to 900 kyr); (2) the 2-D (i.e., map view) structure of the uppermost mantle beneath the spreading axis; (3) the 3-D structure of the crustal magmatic system and (4) the detailed 3-D, shallow crustal thermal structure beneath the Endeavour vent field. The results of imaging will define the recent history of magma supply, the pattern of melt delivery from the mantle to the crust and the structure and segmentation of the subseafloor magmatic and hydrothermal systems.
While at sea, we also obtained a bathmetric map of the Endeavour segment using the Langseth's Simray EM120 12 kHz multibeam system. A preliminary map based on processing at sea is shown below. Preliminary grids are available from my Downloads page. The fully processed grids will be available in 2010.
|A preliminary map showing EM122 bathymetry for the Endeavour segment. Note that the vertical lines visible half way across the image are a result of a pixel registration problem which will be fixed in the final processed map (Full Sized Version)|