Auxiliary Material for Paper 2008GC002354 A record of eruption and intrusion at a fast spreading ridge axis: Axial summit trough of the East Pacific Rise at 9-10 degrees N S. Adam Soule Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA Javier Escartin Groupe Geosciences Marines, Institute de Physique du Globe de Paris, Centre National de la Researche Scientifique, Paris, France Daniel J. Fornari Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA Soule, S. A., J. Escartin, and D. J. Fornari (2009), A record of eruption and intrusion at a fast spreading ridge axis: Axial summit trough of the East Pacific Rise 9-10 degrees N, Geochem. Geophys. Geosyst., 10, Q10T07, doi:10.1029/2008GC002354. Introduction: This supplementary material includes longitude and latitude picks of the boundary (2008gc002354-ts01.txt) and centerline (2008gc002354-ts02.txt) of the axial summit trough. In addition, we include measurements of fault dip angles within the study area that provide constraints on estimates used in models described in the paper. We have tabulated dip angles for AST bounding faults and for an off-axis fault at the EPR from near-bottom multibeam bathymetry and along-track bathymetric profiles. SM2000 multibeam bathymetry data collected over the AST [Soule et al., 2008 - G-cubed] show fault dip angles from 45 degrees to 75 degrees with a mean of 60 degrees (2008gc002354-fs01.eps). We note that these data are gridded at 50 cm horizontal resolution and that this gridding limits the maximum fault dip measurable for a given fault offset. High-resolution bathymetry profiles from TowCam altimetry are used to calculate fault dip angles at the AST margins along the ridge axis and for a near-axis fault near 9 degrees 53'N. We calculate fault dip angles from the best-fit slope to the collection of points defining the entire fault surface and the slope between two to three points defining the steepest portion of the fault. In both data sets, small sections of a given fault (i.e. steps) provide maximum dip angles; fitting a line to a larger section of the fault provide minimum dip angles. Dip angles measured from a fault step, especially one defined by two adjacent points, may include noise within the bathymetry record and result in greater dips than are actually present. Dip angles measured over a collection of points defining the entire fault surface may include mass-wasted material or lava flows that have draped the fault resulting in a lower than expected dip angle. From these data, we conclude that AST bounding faults are rarely vertical in the study area, are typically modified (by talus, draping lava flows, etc.), and that mean fault dips of ~60 degrees-70 degrees are representative. Vertical fractures do not appear to be important component of the total fault length, but we note that if vertical fractures are present and compise up to 25% of the total fault length, below which faults are ~60 degrees, mean fault dip including the deep and shallow protions do not exceed 70 degrees. 1. 2008gc002354-ts01.txt Table S1. Picks of the AST boundary mapped from sidescan sonar data at 50 m intervals along the ridge axis. The points that make up the boundary of each AST segment are listed in serial order, down (N-S) one side of the AST and up (S-N) the other. 1.1 Column "lon", decimal degrees, longitude of pick. 1.2 Column "lat", decimal degrees, latitude of pick. 1.3 Column "id", integer, unique identifier of separate AST segments. 2. 2008gc002354-ts02.txt Table S2. Picks of the AST centerline mapped from sidescan sonar data at 50 m intervals along the ridge axis. 2.1 Column "lon", decimal degrees, longitude of pick. 2.2 Column "lat", decimal degrees, latitude of pick. 2.3 Column "id", integer, unique identifier of separate AST segments. 3. 2008gc002354-fs01.eps Figure S1. SM2000 multibeam bathymetry over the AST at 9 degrees 50'N collected after the 2005-06 eruption [Soule et al., 2008] is gridded at 50-cm horizontal resolution. Profiles across the AST (A-D) are used to estimate fault dip angle which ranges from <50 degrees (when using the collection of depths that define the total offset) to >70 degrees (when looking at small, steep steps within the fault offset). 4. 2008gc002354-fs02.eps Figure S2. Example of TowCam estimates of fault dip from a near-axis (600 m east of ridge axis at ~9 degrees 55'N) inward facing normal fault. TowCam bathymetry data is calculated from a pressure sensor depth and down-looking altimeter height collected at 1 Hz (roughly 10-cm along-track resolution). Light blue lines reflect raw seafloor bathymetry data that contain high-frequency noise on the order of 10'b1cm. Dark blue line is bathymetry data that has been low-pass filtered. Bold red lines show a linear fit to the collection of points across the entire fault offset. Bold blue lines show linear fit to 2-3 points defining a step on the fault surface. 5. 2008gc002354-fs03.eps Figure S3. Example of TowCam estimates of fault dips crossing the AST (AT11-7_CT03 at ~9 degrees 50'N) shown at five times vertical exaggeration. TowCam bathymetry data is calculated from a pressure sensor depth and down-looking altimeter height collected at 1 Hz (roughly 10-cm along-track resolution). Light blue lines reflect raw seafloor bathymetry data that contain high-frequency noise on the order of 10 plus/minus cm. Dark blue line is bathymetry data that has been low-pass filtered. Bold red lines show a linear fit to the collection of points across the entire fault offset. Bold blue lines show linear fit to 2-3 points defining a step on the fault surface. 6. 2008gc002354-fs04.eps Figure S4. Example of TowCam estimates of fault dips crossing the AST (AT11-7_CT13 at ~9 degrees 32'N) shown at ten times vertical exaggeration. TowCam bathymetry data is calculated from a pressure sensor depth and down-looking altimeter height collected at 1 Hz (roughly 10-cm along-track resolution). Light blue lines reflect raw seafloor bathymetry data that contain high-frequency noise on the order of 10 plus/minus cm. Dark blue line is bathymetry data that has been low-pass filtered. Bold red lines show a linear fit to the collection of points across the entire fault offset. Bold blue lines show linear fit to 2-3 points defining a step on the fault surface. 7. 2008gc002354-fs05.eps Figure S5. Example of TowCam estimates of fault dips crossing the AST (AT11-10_CT13 at ~9 degrees 29'N) shown at two times vertical exaggeration. TowCam bathymetry data is calculated from a pressure sensor depth and down-looking altimeter height collected at 1 Hz (roughly 10-cm along-track resolution). Light blue lines reflect raw seafloor bathymetry data that contain high-frequency noise on the order of 10 plus/minus cm. Dark blue line is bathymetry data that has been low-pass filtered. Bold red lines show a linear fit to the collection of points across the entire fault offset. Bold blue lines show linear fit to 2-3 points defining a step on the fault surface. 8. 2008gc002354-ts03.txt Table S3. Table containing fault dips measured from multibeam bathymetry and TowCam bathymetry profiles. All faults are inward-facing normal faults. 8.1 Column "lon", decimal degrees, longitude of fault crossing. 8.2 Column "lat", decimal degrees, latitude of fault crossing. 8.3 Column "face", dip-direction of fault. 8.4 Column "dip", degrees, dip-angle of fault. 8.5 Column "length%", percentage of entire fault exposure length in the direction of fault dip used for measurement. 100% is the entire fault, smaller length percentages reflect short, fault steps. 8.6 Column "pos", position of the fault relative to the ridge axis (AST or off-axis). 8.7 Column "source", name of data source (e.g., TowCam deployment).