Source processes and seismotectonic implications of the 1995 and 1996 Cyprus, Eastern Mediterranean region, earthquakes

The teleseismic body waves of two earthquakes were inverted for their sourc es to obtain a rupture process for each. The February 23, 1995 (M-s = 5.8) and October 9, 1996 (M-s = 6.8) events took place to the northwest and sout hwest of Cyprus. Both the earthquakes generated complex body waveforms whic h were inverted using the method of Kikuchi and Kanamori (1991). The invers ion results suggest that the 1995 and 1996 events were multiple events asso ciated with subevents taking place on different faults located nearby the s ource regions. Three subevents were necessary to explain the waveforms of t he 1995 earthquake. The first subevent showed a predominantly normal faulti ng mechanism while the second subevent, located 20 km to the north of the f irst subevent, had a strike-slip mechanism with dip-slip component. Despite the difference in mechanisms both the subevents had slip vectors oriented nearly E-W. The last subevent was located in the proximity of the first sub event and had a normal faulting mechanism with a slip vector in N-S directi on. The different depths and slip-vector directions of the first and third subevents may suggest strain partitioning with depth in the source region o f the 1995 event. The complex waveforms of the 1996 earthquake were modeled with three subevents, too. Combining the hypocentral distribution of the a ftershocks with the inversion results revealed that the first subevent took place on a fault plane dipping about 20 degrees to the east-southeast. The mechanism of the first subevent, together with the azimuthal pulse-width d istribution suggest that the sense of motion on the fault plane was right-l ateral strike-slip and unilateral rupture propagation. We estimate from the major subevent a slip rate of 10 mm/year for the African plate. The second and third subevents were located 35 km to the southeast of the main shock and had a predominantly normal faulting mechanism with slip vectors in nort h-northwest direction. The rupture process analysis of the 1995 and 1996 ev ents suggests that the region to the west of Cyprus experiences extensional tectonics. (C) 1999 Elsevier Science B.V. All rights reserved.