Shear Wave Velocity Structure from Interface Waves at Two Deep Water Sites in thePacific Ocean

摘要

The shear wave velocity structure of two deep ocean sites has been studied bydetonating explosives on the ocean floor and examining the slowly moving Stoneley waves that were generated at the ocean floor interface. At the southern California site, the structure was found to be uniform insofar as the relatively sparse sampling can resolve. At the central California site, the velocities and velocity gradients were found to be variable over the space of 1 or 2 km. At both sites, the shear wave velocity at the seafloor is very low, between 27 and 32 m/s. The shear wave velocity gradient at the southern California site in the top 1 m of the sediments is 5.2 m/s(sm), and 3.1 m/s(sm) in the next 100 m. At the northern site, the velocity gradient for the top 1 m varies between 5.0 m/(sm) and 8.0 m/(sm), and for the next 20 m it varies between 4.5 m/(sm) and 7.0 m/(sm).