Faulted Structure of the Bottom Simulating Reflector on the Blake Ridge, Western North Atlantic

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 approx. 440-m-thick section of hydrate bearing sediment overlying and approx. 5- m-thick layer of methane gas-rich sediment. The high resolution attainable by the deep-tow seismic system reveals normal fault offsets of approx. 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 off set of the BSR itself reflects discontinuities in the pressure- temperature field across the fault zones where they intersect the BSR. Directional ambient noise, Bottom scattering, Deep-towed array geophysical system, Ocean-bottom seismometer, Towed array.