A broadband P wave analysis of the large deep Fiji Island and Bolivia Earthquakes of 1994

The complex broadband P-wave displacement recordings of the 570 km deep March 9, 1994, M_w 7.6 Fiji Island and the 660 km deep June 9, 1994, M_w 8.2 Bolivia earthquakes are analyzed to estimate the spatial and temporal characteristics of their ruptures. We model relative arrival times and amplitudes of coherent subevents in P waveforms, and perform waveform analyses. We resolve: (1) short rupture durations relative to their seismic moments, 12 and 40 s for the Fiji and Bolivia earthquakes, respectively; (2) small areas of main moment release, for both earthquakes 30 × 40 km²; (3) high stress drops compared to shallow earthquakes, with the stress drop of the Bolivia event (283 MPa) being significantly higher than the stress drop of the Fiji event (26 MPa); (4) small changes in mechanism (up to 10° changes in fault plane orientation); and (5) a steeply dipping rupture plane for the Fiji earthquake, and a shallowly dipping rupture plane for the Bolivia earthquake. Details of the ruptures are difficult to resolve using teleseismic P waveforms.