HR: 1340h
AN: T33A-0512    [Abstracts]
TI: Upper Crustal Evolution Along the Juan de Fuca Ridge Flanks and its Relation to Sedimentation and Tectonic History
AU: * Nedimovic, M
EM: mladen@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory of Columbia University, 61 Route 9W, P. O. Box 1000, Palisades, NY 10964 United States
AU: Carbotte, S
EM: carbotte@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory of Columbia University, 61 Route 9W, P. O. Box 1000, Palisades, NY 10964 United States
AU: Newman, K
EM: knewman@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory of Columbia University, 61 Route 9W, P. O. Box 1000, Palisades, NY 10964 United States
AU: Diebold, J
EM: johnd@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory of Columbia University, 61 Route 9W, P. O. Box 1000, Palisades, NY 10964 United States
AU: Babcock, J
EM: jbabcock@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Harding, A
EM: aharding@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Kent, G
EM: gkent@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Canales, P
EM: canales@whoi.edu
AF: Woods Hole Ocenographic Institution, 360 Woods Hole Rd, Woods Hole, MA 02543 United States
AU: Detrick, R
EM: rdetrick@whoi.edu
AF: Woods Hole Ocenographic Institution, 360 Woods Hole Rd, Woods Hole, MA 02543 United States
AB: To study upper crustal evolution along the Juan de Fuca (JDF) ridge flanks we gather velocity structure information by analyzing multichannel seismic (MCS) data collected during the 2002 EW0207 cruise. We first produce about 6000 constant offset stack super CMP gathers, each formed by combining 12 adjacent CMP gathers. Then we select for analysis some 300 of the produced super gathers that are located over a relatively smooth igneous basement and are characterized by high signal-to-noise ratio. Finally, we use JDSEIS software to model in 1D the identified travel time arrivals. The obtained results accurately reveal regional 2A velocity increases and 2A thickness changes associated with crustal alteration that are clearly linked to the patterns of sedimentation across the JDF ridge. Shorter wavelength variations, superimposed on the long-term systematic trends, are also apparent. These local variations in the thickness of layer 2A appear to be associated with the abyssal hill topography inherited from crustal accretion, and are perhaps spatially tied to the principal inward facing scarps. We also observe local increase in 2A velocity associated with propagator wakes along the eastern sedimented ridge flank, with the most prominent velocity anomaly at Endeavour transect. Despite the great density of our layer 2A velocity analysis done on super CMP gathers, detailed upper crustal velocity information cannot be accurately extracted from our modeling because of the limitations of the employed 1D approach. Continuous high-resolution velocity investigations along the ridge flanks, where topography and crustal structure often rapidly change laterally, require advanced velocity analysis techniques such as is 2D waveform tomography, methodology that we plan to apply in the near future. Detailed, high-resolution velocity images are essential for evaluating patterns of upper crustal heterogeneity and their linkages to long-term hydrothermal circulation systems.
DE: 7220 Oceanic crust
DE: 7245 Mid-ocean ridges
SC: Tectonophysics [T]
MN: Fall Meeting 2005