FAULTED STRUCTURE OF THE BOTTOM SIMULATING REFLECTOR ON THE BLAKE RIDGE, WESTERN NORTH-ATLANTIC

High-resolution multichannel seismic data collected from the Blake Rid ge in the western North Atlantic by the Naval Research Laboratory's De ep Towed Acoustics/Geophysics System (DTAGS) show that the bottom simu lating reflector (BSR) in this area is the reflection from the interfa ce between an approximately 440-m-thick section of hydrate-bearing sed iment overlying an approximately 5-m-thick layer of methane gas-rich s ediment. 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 ini tially concentrated beneath the hydrate-bearing sediment, enabling hyd rate to form throughout sediment above the BSR. Because the BSR repres ents a methane gas-methane hydrate phase boundary rather than a lithol ogic or diagenetic horizon, the observed offset of the BSR itself refl ects discontinuities in the pressure-temperature field across the faul t zones where they intersect the BSR.