Faulted structure of the bottom simulating reflector on the Blake Ridge, western North Atlantic

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Abstract
High-resolution multichannel seismic data collected from the Blake Ridge in the western North Atlantic by the Naval Research Laboratory's Deep Towed Acoustics/Geophysics System (DTAGS) show that the bottom simulating reflector (BSR) in this area is the reflection from the interface between an approximately 440-m-thick section of hydrate-bearing sediment overlying an approximately 5-m-thick layer of methane gas-rich sediment. The high resolution attainable by the deep-tow seismic system reveals normal-fault offsets of approximately 20 m in the BSR. These growth faults may provide a path for vertical migration of methane initially concentrated beneath the hydrate-bearing sediment, enabling hydrate to form throughout sediment above the BSR. Because the BSR represents a methane gas-methane hydrate phase boundary rather than a lithologic or diagenetic horizon, the observed offset of the BSR itself reflects discontinuities in the pressure-temperature field across the fault zones where they intersect the BSR.