Velocity structure of the methane hydrate formation at the Blake Outer Ridge

• Main Author: Christine Ecker
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Haskell; Methane hydrate
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.386.2741; http://sepwww.stanford.edu/data/media/public/docs/sep84/christin2.pdf

Seismic analysis of data from the Blake Outer Ridge indicates the presence of hydratebearing sediments overlaying gas-saturated sediments in this region. In an attempt to determine possible lateral and vertical variations of the hydrate and gas sediments, I performed a 2-D velocity analysis along two approximately perpendicular seismic lines. Subsequent determination of the seafloor and BSR reflection coefficients along one of the lines resulted in additional zero offset P-wave velocity and density constraints. Combining these with the average interval velocity model of this line, I performed a 1-D elastic amplitude modeling of zero offset reflections using the Thompson-Haskell reflectivity method. The results suggest that regions showing a continuous bottom simulating reflection are characterized by a thick hydrate layer that has an average velocity of 2.1 km/s overlaying low-velocity ( ≈ 1.6 km/s) sediments of considerable thickness. This result agrees well with results discussed in SEP80. In regions of discontinuous BSR, a less pronounced velocity contrast is visible, probably indicating a decrease in the hydrate concentration of the sediments.