Mid-Ocean Ridges: A Connected System Hydrothermal circulation links ocean, seafloor, and crust, including vent communities How is fluid circulation controlled by faulting, fracture systems, and magma chamber? How does crust evolve? –Layer 2A –Magma chamber 3-D seismic reflection can tie seafloor geology to subsurface at m resolution Nedimovic et al. (2008) Carbotte et al. (2006), Van Ark et al. (2007)

2-D Seismic Survey over Endeavour Segment Along-axis and cross-axis seismic lines acquired in 2002 (Carbotte et al, 2006) 2-D surveys have much lower resolution than 3-D Microseismicity studies around vent fields (Wilcock et al., 2002)

Along-Axis Seismic Line Reflector from layer 2A: alteration boundary or top intrusives Underlying axial magma lens correlates with seismicity under vent fields Melt reflector is out-of-plane of 2-D profile: correct positioning requires 3-D Van Ark et al. (2007)

Cross-Axis Seismic Line Reflector from layer 2A: alteration boundary or top intrusives or both Underlying restricted axial magma lens dips to east, and sometimes correlates with seismicity under vent fields Van Ark et al. (2007)

Seismicity Above Axial Magma Chamber Seismicity pattern consistent with fracturing above inflating magma sill Inflation of AMC facilitates heat transfer, and may control seafloor vent distribution Can these faults be imaged by 3-D surveys? Wilcock et al. (2009)

Streamer Tomography and Hydrothermal Circulation High resolution seismic velocity models from towed streamer recording Fluid migration in oceanic crust inferred from velocities and disruption of reflector at base of layer 2A Newman et al. (in prep)

3-D / 4-D Seismic Proposal (Carbotte, Nedimovic et al.) Endeavour is focus of a broad range of geoscience studies Understanding seafloor and ocean processes requires detailed knowledge of subsurface 3-D seismic reflection surveys can image structures at a “geological scale” Long-term monitoring also requires knowledge of subsurface changes from repeat surveys Velocity models can be used for earthquake location

3-D / 4-D Seismic Proposal (Carbotte, Nedimovic et al.) 3-D seafloor topography and fine-scale structure require 3-D seismic imaging –Relation between faulting and magma distribution –Controls on hydrothermal venting by faults, crack systems, and melt –3-D fluid circulation constraints Baseline 3-D survey for long-term site monitoring of seismicity, fluid chemistry, microbiology etc. by NEPTUNE Canada –Subsurface evolution by differencing of monitoring surveys (10 year intervals?) Possible survey sites: Endeavour vent fields, Axial Volcano, East Pacific Rise –Long-term monitoring of Endeavour by Neptune Canada EPR OSC Kent et al. (2001) 3-D Result with 1980s Technology