Research > Endeavour Tomography

The Endeavour Tomography experiment (ETOMO) is funded by the National Science Foundation and after two delays due to ship availability issues is now scheduled for the summer of 2009.

The goal of this collaborative experiment involving the Universities of Oregon and Washington are to distinguish between competing models for what controls the segmentation and intensity of ridge crest processes are at odds on the scale of mantle and crustal magmatic segmentation, the distribution of hydrothermal venting with respect to a volcanic segment 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 reflector beneath 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.  We propose a seismic experiment to investigate the 3-D structure of the crust and topmost mantle beneath the Endeavour segment, a RIDGE2000 Integrated Study Site (ISS).  The scientific objectives are to:  (1) Determine if the segmentation and intensity of the magma-hydrothermal systems at the Endeavour ridge are related to magma supply or to the magma plumbing between the mantle and crust, and (2) Constrain the thermal and magmatic structure underlying the Endeavour hydrothermal system in order to understand the patterns of energy transfer. 

Design of the 3-D seismic tomography experiment. OBSs indicated by yellow circles. The Vent Field and Crustal Magma Chamber grids for airgun shooting (purple and yellow rec-tangles, respectively) are centered on the vent fields. Off-axis rise-parallel shooting lines are shown in red. Shot spacing described in text. Faint black lines indicate existing multichannel seismic profiles. Thick black lines show the approximate location of the axial magma chamber reflector Stars indicate vent fields. (Full Sized Version)

An active source seismic tomography experiment, using an array of 64 three-component ocean-bottom seismometers, will image the 3-D seismic structure of the crust and topmost mantle along an 80-km-long section of the Endeavour ridge.  The experiment will 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.