Analysis of Bottom Simulating Reflections in the Blake Ridge 2D Seismic Reflection Data

Abstract

During the summer of 2023 I participated in a 2D seismic cruise on Blake Ridge. In this thesis, I analyze seismic reflection Lines 1001 and 1003 that were processed during the cruise. My interpretation is focused on identifying evidence for natural gas hydrate in near seafloor sediments. Gas hydrate is an ice-like substance that contains a highly concentrated source of methane. In seismic data, I look for and map bottom simulating reflections, which serve as indicators for the presence of gas hydrate. These reflections appear at the bottom of the gas hydrate stability zone. Line 1001 contains a clear, continuous BSR. Using the TgradBSR, an application that estimates the depth of the BSR, I calculated the thermodynamic base of gas hydrate stability. This requires pressure, salinity, seafloor temperature data, and the geothermal gradient. Using two different geothermal gradients from Ocean Drilling Program Leg 164, Site 994 and 995, two estimates of the BSR depth were calculated. The observed BSR depth was shallower than the two estimates. The change in the seafloor temperature and the P-wave velocities may have affected the depth of the BSR to some extent, but the greatest factor affecting the depth of the BSR was the geothermal gradient. Using a higher geothermal gradient of 39.6 °C/km, compared to Sites 994 and 995, the estimated BSR depth matches the observed BSR depth.A five-year embargo was granted for this item.Academic Major: Earth Science