Event 3
In the Nacar Trench, excavated across the
East Anatolian Fault Zone,
Karabacak et al. (2012:310–315) identified a
sequence of surface-rupturing earthquakes recorded
within a narrow (~8–10 m) fault zone cutting both
ophiolitic basement and overlying sedimentary units.
Event 3, the youngest event identified in the
trench, is expressed along the main fault branch
adjacent to unit b and is marked by fractures that
cut units h, i, and j before terminating beneath
the present soil. The rupture is also associated
with a ~20 cm wide fault fill between units b and
j, indicating the development of an open fracture
zone during surface faulting.
Additional fractures attributed to this event
occur elsewhere in the trench, juxtaposing
different stratigraphic units and likewise
terminating below the current soil horizon. These
relationships indicate that the rupture reached
the surface and was subsequently buried by soil
formation, marking a clear event horizon at the
base of the modern ground surface.
The geometry of the fault planes, dipping at
10–30°, indicates oblique slip with a compressional
component superimposed on strike-slip motion. The
localization of deformation along pre-existing
structures suggests that Event 3 reactivated
earlier fracture networks while propagating to the
surface, consistent with repeated use of the same
fault zone through time.
Radiocarbon and OSL dates from sedimentary units
above and below the event horizon suggest that
this rupture may correspond to the
1114 CE Marash earthquake.
