Variations in shear-wave splitting in young Pacific seafloor

Analysis of SKS phases recorded by ocean-bottom seismometers in the GLIMPSE Experiment has expanded the region of in situ measurements of shear-wave splitting in young seafloor near the southern East Pacific Rise. Average splitting times at individual GLIMPSE sites range from 1.1 to 2.2 s with fast direction azimuths trending approximately in the direction of absolute plate motion and fossil spreading for the Pacific plate. The GLIMPSE study area at 12 to 14degreesS is adjacent to the MELT Experiment. The new observations demonstrate that splitting delays are not uniform on the Pacific plate and that the contrast between the Nazca and Pacific plates is not a fundamental consequence of the asymmetric plate motion. The variations in degree of splitting could be caused by small-scale convection, variations in water content, or rate of deformation in the asthenospheric return flow to the East Pacific Rise.