A BROAD-BAND 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 dee p 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 an d temporal characteristics of their ruptures. We model relative arriva l times and amplitudes of coherent subevents in P waveforms, and perfo rm waveform analyses. We resolve: (1) short rupture durations relative to their seismic moments, 12 and 40 s for the Fiji and Bolivia earthq uakes, respectively; (2) small areas of main moment: release, for both earthquakes 30x40 km(2); (3) high stress drops compared to shallow ea rthquakes, with the stress drop of the Bolivia event (283 MPa) being s ignificantly higher than the stress drop of the Fiji event (26 MPa); ( 4) small changes in mechanism (up to 10 degrees changes in fault plane orientation); and (5) a steeply dipping rupture plane for the Fiji ea rthquake, and a shallowly dipping rupture plane for the Bolivia earthq uake. Details of the ruptures are difficult to resolve using teleseism ic P waveforms.