Three-dimensional seismic imaging of the Blake Ridge methane hydrate province: Evidence for large, concentrated zones of gas hydrate and morphologically driven advection

Current estimates for the amount of methane trapped below gas hydrate provinces remain highly speculative, and explanations for how this methane is injected into the atmosphere are wide-ranging and unverified. Blake Ridge, one of the largest passive margin gas hydrate provinces on Earth, is traditionally characterized as an expansive yet dilute reservoir of methane hydrate with no significant fluid advection. Previous 2-D seismic analysis and Ocean Drilling Program Leg 164 drilling results show evidence for both concentrated zones of hydrate and possible fluid flow; however, the extent of these phenomena remains ambiguous. Here we analyze high-resolution 3-D seismic data collected at Blake Ridge in 2000 and map seismic indicators of concentrated hydrate and fluid flow. We also use the seismic data to map the base of the gas hydrate stability in 3-D. Our analysis demonstrates that the gas hydrate phase boundary varies significantly in areas of high sedimentation and erosion, suggesting a dynamic hydrate system. Furthermore, evidence of localized bottom-simulating reflector shoaling, particularly at a sediment wave bounding surface, indicates ongoing advection. The analysis reveals that the Blake Ridge gas hydrate system is significantly more dynamic than previous studies suggest, and we hypothesize that fluctuating sedimentation and erosion patterns cause hydrate phase-boundary instability that triggers fluid flow.