Seismic refraction observations north of the Brownson Deep*

Abstract

Abstract Results of several refraction profiles made on the rise to the north of the Brownson Deep are presented. Good evidence for a high-speed layer with travel-time curves showing a compressional velocity of 7.94 km/sec. and an intercept of 8.4 sec. is presented, and the presence of an overlying lower-speed layer (6.64 km/sec., intercept 8.1 sec.) is demonstrated on less complete evidence. Neither layer correlates with existing reflection data in the area. Two sets of secondary low-frequency arrivals are tentatively interpreted as a refracted shear wave and a wave that has taken a bottom and surface reflection and then a basement refraction. Evidence is presented for a newly observed forerunner of the refracted-surface reflected waves of the permanent sound channel (RSR waves) consisting of a train of nearly constant frequency waves which appear to travel between surface and bottom via the RSR path and along the bottom at the speed of sound in water at the bottom.