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Earthquakes in the “aseismic” regions of the western Pacific

1986; American Geophysical Union; Volume: 13; Issue: 3 Linguagem: Inglês

10.1029/gl013i003p00169

1944-8007

K. J. Muirhead, R. D. Adams,

High-pressure geophysics and materials

Operators of a deep ocean hydrophone array near Wake Island in the northwest Pacific Basin have located several previously unreported earthquakes within 20° of Wake Island in the "aseismic" interior of the Pacific plate, and have suggested high attenuation in the source region to explain why these events have not been reported by seismological agencies. The largest such earthquake occurred on 1983 June 29, in the Kiribati region; readings were submitted to the International Seismological Centre, but the earthquake was excluded from the final analysis because of doubt about its location and interfering arrivals from other earthquakes. Closer examination now provides a well‐determined seismological location and a magnitude of 4.7 (mb). Neither amplitudes nor frequency content of Australian records of the Kiribati earthquake support the existence of a region of abnormally high attenuation beneath the source. We suggest that the higher magnitudes reported from the hydrophone measurements result from the efficient coupling of energy from shallow intraplate earthquakes in the Pacific Basin into the P o /S o waveguide.