Akademik Veri Yönetim Sistemi
73. Türkiye Jeoloji Kurultayı, Ankara, Türkiye, 24 - 28 Mayıs 2021, ss.67-69
On Friday, January 24, 2020 at 20.55 local time, an earthquake with a magnitude of
Mw = 6.8 has occurred in Sivrice district of Elazığ. The focal mechanism solution is consistent
with pure left-lateral strike-slip faulting; the location of the epicenter and fault mechanism
suggest deformation along the Pütürge Segment of the East Anatolian Fault Zone. A 10-day
fieldwork was carried out along the Pütürge Segment to study surface deformation; the geometry
of the surface rupture and other seismic geomorphological structures were mapped and
studied. The field data is also correlated with satellite images. This paper therefore presents
classification of seismic geomorphological structures and discuss intimate relationship between
fault geometry and stress field in the region.
Seismic geomorphological deformation and related features of the Sivrice (Elazığ) earthquake
are observed in the area between Gezin (Elazığ) and Ormaniçi (Pütürge) villages; they
are classified into two as seismotectonic and seismo-gravitational features. Surface rupture
and cracks, uplifted and subsiding topography and elongated pressure ridges are common
seismotectonic surface features. Seismo-gravitational surface features include structures related
to mass movements, lateral spreading and liquefaction. Field observations confirm that
seismo-gravitational structures develop along both Gezin-Sivrice-Doğanbağı and Doğanbağı-
Çevrimtaş-Ilıncak-Koldere-Ormaniçi sections of the Pütürge Segment while surface rupture Koldere-
Ormaniçi section. Small-scale landslides, rock falls, feather cracks along asphaltic roads,
and laterally discontinues ground failure-related features are common seismo-gravitational
structures that developed along the fault zone. In addition, small-scale lateral spreading and
liquefaction structures are common especially in areas where fault-perpendicular streams
meet the Karakaya Dam reservoir. The surface rupture is mapped as stepping and overlapping
en echelon fractures along elongated pressure ridge between Çevrimtaş and Doğanbağ villages,
to northwest of Ilıncak village, along 1.5-km-long pressure ridge between Topaluşağı and
Doğanyol, across the elongated hill that developed on an alluvial fan to the northwest of Doğanyol
and in the area between Koldere and Ormaniçi villages. Surface fractures deforming
the pressure ridges are all aligned parallel to the long axes of the ridges. They also display
reverse components and define small-scale pop-up structures.
Interferometric SAR (DInSAR) studies indicate a 10-cm uplift in the northwestern block of
the fault and a 6-cm subsidence in the southeast block. The difference in vertical movements
between two blocks of the fault is interpreted to suggest that at least 30-km-long section of the
Pütürge Segment in the area between southwest of Sivrice and Pütürge is broken during the
main shock. Although the focal mechanism solution of the main shock gives pure left-lateral
strike-slip faulting, there is no significant left-lateral displacement observed during the fieldwork.
This can be explained by followings: (i) left-lateral strike-slip displacement was not
able to reach the surface; (ii) left-lateral torque movement of the fault around a vertical axis
during the earthquake, (iii) restraining bend nature of the Pütürge Segment, or (iv) the presence
of Pütürge metamorphics along the fault strike. It is also important to note that along most
part of the Pütürge Segment where surface rupture is observed, talus, colluvial or alluvial fan
sediments are exposed; unconsolidated and/or poorly consolidated nature of these sediments
may also be counted as one of the main reason for not observing horizontal displacement on
the surface.