Hydrothermal seepage patterns above a buried basement ridge, eastern flank of the Juan de Fuca Ridge

proportion ofhemipelagic material, from 2 � 10 � 16 m 2 at30% hemipelagic to6 � 10 � 18 m 2 at 95% hemipelagic. Modeled seepage rates, derived from basement overpressures and sediment physical properties, range from 0 to 27 mm/yr. The average seepage rate over the entire 11 km of ridge within our study area is 1.3 mm/yr. On the basis of the model results, half of the total volume flux of seepage from the First Ridge is contributed from 25% of the study area, with flow rates � 1.1 mm/yr. Low seismic reflection amplitude anomalies are generally correlated with areas of high seepage rates. INDEX TERMS: 1815 Hydrology: Erosion and sedimentation; 1832 Hydrology: Groundwater transport; 3015 Marine Geology and Geophysics: Heat flow (benthic) and hydrothermal processes; 3022 Marine Geology and Geophysics: Marine sediments—processes and transport; 3025 Marine Geology and Geophysics: Marine seismics (0935);

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