Till beneath ice stream B: 1. Properties derived from seismic travel times

摘要: Seismic experiments conducted on ice stream B, part of the marine sheet West Antarctica, show a meters-thick layer immediately beneath 1000-m-thick ice. A seismic experiment consisting wide-angle reflection profiling along line parallel to flow was determine properties this layer. Inversion travel times yields compressional wave speed less than 1700 m s−1 and shear 160 for These very low speeds imply that material in is highly porous saturated with water at high pore pressure. Based other saturated, unconsolidated sediments, we believe porosity substantially greater 0.32, probably around 0.4, an excess overburden pressure over only 50 kPa (0.5 bar) characterize location.