SOURCE INVERSION OF THE 1993 AND 1995 GULF OF AQABA EARTHQUAKES

The teleseismic body waves of two earthquakes were inverted to their s ources so as to obtain a rupture process for each. The events of Augus t 3, 1993 (M-s = 6.1) and November 22, 1995 (M-s = 7.2) took place at the southern end of the Dead Sea fault system (DSFS), which has been s eismically quiet for the last few centuries. The inversion results sho w that the rupture of the 1995 event originated in the vicinity of the 1993 event and propagated to the north where the major moment release of two subevents took place, the first being 20 km and the second bei ng 40 km away. The seismic moment of the first and second subevents we re M, = 7.4 x 10(18) Nm and M-o = 38 x 10(19) Nm, respectively. Despit e their proximity, they show completely different focal mechanisms. Th e first subevent has a predominantly normal faulting mechanism like th e 1993 event which probably took place on the faults forming the pull- apart basins beneath the Gulf of Aqaba. The major subevent shows a pre dominantly left-lateral strike-slip mechanism which clearly identifies the DSFS as accommodating the motion between Africa and Arabia. We at tribute the abrupt change of the mechanisms of the 1993 and 1995 event s to segmentation of the DSFS beneath the Gulf of Aqaba which probably gave rise to an extensional regime. The locations of the 1993 and 199 5 earthquakes, their aftershock distribution and the spatial distribut ion of the subevents of the 1995 earthquake, show end-to-end migration of sources from south to north. Taking into account the long seismic quiescence of the DSFS and the source inversion results, one may concl ude that the area to the north of the rupture zone of the 1995 event i s prone to a large earthquake.