DIRECTIVITY ANALYSIS OF THE DEEP BOLIVIAN EARTHQUAKE OF JUNE 9, 1994

The June 9, 1994 deep Bolivian earthquake (M(W) = 8.3, d = 636 km) occ urred on a nearly horizontal rupture plane with an approximate area of 2000 km(2). The rupture plane is constrained by directivity analysis of the P wave displacement pulses recorded at local, regional, and tel eseismic distances. The fact that there are local recordings of the di splacement provides a strong constraint on the vertical extent of faul ting, which is less than similar to 10 km. The moment release had at l east four distinct episodes, or subevents. The best overall explanatio n for the subevents is rupture which initiates on the western margin o f the fault plane, propagates to the east, and then continues bilatera lly along a 350 degrees azimuth with most of the moment release occurr ing to the north. The apparent rupture velocity between subevents is v ery low, approximately 1-2 km/s.