The Makapuu Ocean Bottom Seismograph, located 10 km off the southeast coast of Oahu in the Hawaiian Islands, recorded 359 events from July 30, 1976 to March 30, 1977. Sixty-five epicenter locations indicate that most of these events are Hawaii Island activity; however, events apparently unrelated to Hawaii Island volcanic activity occur near the Hawaiian Ridge including: (1) an unusual event near Niihau Island (ML>4.0); (2) three events (ML?3--3.5) near Maui and Kahoolawe islands indicating active faulting or perhaps extension of rift zones; (3) events south of the Hawaii Island, several corresponding to seamounts with historical seismic activity that may be related to submarine volcanism and associated periods of slumping and readjustment; (4) an offshore earthquake northeast of Oahu (ML ~4.0) that was felt along the coast of the island. About 40% of the events not associated with Hawaii Island were undetected by land-based stations. This study indicates that the Hawaiian Ridge may be more seismically active then previously thought. |