THE COMPLEX RUPTURE PROCESS OF THE 1996 DEEP FLORES, INDONESIA EARTHQUAKE (M-W 7.9) FROM TELESEISMIC P-WAVES

From an analysis of broadband teleseismic P-waveforms we resolve the c omplex rupture characteristics of the 17 June 1996, Flores earthquake (M-w 7.9, depth 590 km). This earthquake was unusual because of its la rge rupture length and the variation in rupture velocity and stress dr op. The 20 s rupture propagated westward at 2-3 km/s to a distance of 20-30 km, and eastward at 4 km/s over 75 km. Average static stress dro p was about 15 MPa, but the stress drop during the episode of main mom ent release was a factor of four higher. The oblique normal faulting m echanism is consistent with the stress expected as the slab descends a long a highly curved trench. Significant rupture complexity is also re ported for the deep 1994 M-w 7.7 Fiji and M-w 8.2 Bolivia earthquakes and is evident in the source-time functions of many smaller earthquake s at depths > 300 km. Thus source complexity of deep earthquakes appea rs no less common than for shallow earthquakes, and requires the exist ence of significant heterogeneity in the physical properties that cont rol deep earthquake rupture.