Seismicity of the South Pacific ocean

Abstract

A map of earthquake epicenters is presented for the South Pacific Ocean for the period 1957 to 1963. For much of this region the accuracy in locating epicenters has been improved by nearly an order of magnitude in comparison with that of previous studies. In several areas of the South Pacific the seismic activity is confined to narrow zones that are less than 50 km wide. Near 55°S and between 122° and 135°W the pattern of epicenters is offset approximately 1000 km. Seismic and bathymetrie data indicate that a fracture zone intersects the Easter Island ridge in this region. Epicentral data suggest that several other fracture zones may be present in the South Pacific and eastern Indian oceans. Regions of relatively high seisrnicity on the oceanic ridges may be related to the presence of fracture zones that intersect the crest of the ridge. Seismic activity along these fracture zones is restricted almost exclusively to the region between the displaced crests of the oceanic ridge. A number of topo-graphic profiles across the oceanic ridges in the South Pacific and eastern Indian oceans are compared with the epicentral determinations.