This is a microseismic study of the East Pacific Rise at 9 degrees 50 minutes north to provide constraints on shallow magmatic and hydrothermal processes. The study will locate areas of seismic activity and compare them to seafloor geological features, determine the depth extent of microseismicity to delimit the region of brittle fracture, and test whether the seismicity is migrating along the ridge. Two deployments of ocean-bottom seismometers will be conducted; the first to delineate regions of high microseismicity, and the second to provide for accurate hypocenter locations.