Seismicity of the interiors of plates in the Pacific Basin



Historical listings of instrumentally recorded earthquakes raise serious questions about the validity and usefulness of the long-held presumption that the interiors of ocean plates are aseismic stable masses. Unusual distributions of epicenters within these regions may indicate stress patterns resulting from plate motions, or may indicate nascent subduction zones, ridge systems, or hot spots.

Data recorded on ocean-bottom hydrophones and seismometers in an earlier investigation [Walker and McCreery, 1988] revealed 28 intraplate earthquakes in the deep interior of the Northwestern Pacific Basin that were unreported by the worldwide network of land-based seismic stations. The data sources included drum recordings of hydrophones near Wake and Enewetok islands in operation for different time intervals from 1963 through 1969, tape recordings from a 9-element 1500-km-long linear array of hydrophones in operation for 2 months in 1981, and tape recordings from September 1982 through 1985 of an 8-element hydrophone array near Wake Island.