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The neotectonics of southeast Turkey, northern Syria, and Iraq: the internal structure of the Southeast Anatolian Wedge and its relationship with recent earthquakes

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Turkish Journal of Earth Sciences

Turkish J Earth Sci
(2017) 26: 105-126
© TÜBİTAK
doi:10.3906/yer-1605-21

http://journals.tubitak.gov.tr/earth/

Research Article

The neotectonics of southeast Turkey, northern Syria, and Iraq: the internal structure of
the Southeast Anatolian Wedge and its relationship with recent earthquakes
1,

1

1

2

Gürol SEYİTOĞLU *, Korhan ESAT , Bülent KAYPAK
Department of Geological Engineering, Tectonics Research Group, Ankara University, Gölbaşı, Ankara, Turkey
2
Department of Geophysical Engineering, Ankara University, Gölbaşı, Ankara, Turkey
Received: 26.05.2016

Accepted/Published Online: 10.02.2017

Final Version: 15.06.2017


Abstract: In southeastern Turkey, northern Syria, and Iraq, the Southeast Anatolian Wedge (SEAW) is recognized as lying between
the high altitude Bitlis–Zagros Suture Zone and the Sincar Mountains on the Mesopotamian plain. This wedge narrows towards the
south and contains several thrust and blind thrust zones merging with the basal thrust zone. These zones are determined mainly by
locations of fault-propagation folding that generally limit the Plio-Quaternary/Quaternary plains in the region. The positions of these
active thrust/blind thrust zones and their relationships to the right and left lateral faults may be used to explain the seismic activity of
the region.
Key words: Neotectonics, southeast Turkey, Syria, Iraq, earthquake, thrust

1. Introduction
The neotectonics of southeastern Turkey began after the
collision of Arabian and Eurasian plates along the Bitlis–
Zagros suture zone (Şengör, 1980; Şengör and Yılmaz, 1981;
Şengör et al., 1985). The collision history starts during
the Late Maastrichtian–Early Eocene and final contact of
the continents and formation of the zone of imbrications
take place in Late Miocene times (Hall, 1976; Şengör and
Kidd, 1979; Aktaş and Robertson, 1984; Yılmaz, 1993).
Recently, Robertson et al. (2016) distinguished three
main tectonic phases in Southeastern Turkey: during the
Late Campanian, Early Eocene, and Early Miocene. The
intracontinental convergence is also continuing in the
present day (Şengör and Kidd, 1979; Şaroğlu and Güner,
1981; Allen et al., 2004; Reilinger et al., 2006; Aktuğ et al.,
2016).
In contrast to the earlier evaluations of thick
continental crust (e.g., 55 km, Dewey et al., 1986), recent
studies demonstrate that eastern Turkey has a 45-kmthick crust with an accretionary complex supported by
asthenospheric cushioning (Keskin, 2003; Şengör et al.,
2003, 2008).
Tectonic studies have mainly focused on the structures

located in the north of the Bitlis–Zagros suture zone
(Yiğitbaş and Yılmaz, 1996; Oberhanslı et al., 2010; Okay
et al., 2010) but the structures of the Arabian foreland
were poorly studied (Lovelock, 1984; Biddle et al., 1987;
*Correspondence: seyitoglu@ankara.edu.tr

Perinçek et al., 1987; Gilmour and Makel, 1996) and only
the fold axes are shown on the maps (Şengör et al., 1985,
2008; Yılmaz, 1993; Okay, 2008). The Zagros foreland,
however, is relatively well studied in terms of blind
thrusting, seismicity, and GPS data (Berberian, 1995;
Hatzfeld et al., 2010; Agard et al., 2011) (Figure 1).
The existing active fault map of Turkey (Emre et al.,
2013) does not explain the correlation with all seismic
events, especially in southeastern Turkey. Most of the active
faults are of a strike–slip nature and are recognized after
major earthquakes in eastern Turkey (i.e. Çaldıran, Varto,
Bingöl). Active thrust fault lines are rare on the MTA map,
with the exception of the Bitlis Suture Zone, and the Van
and Cizre Faults, whose limited identification is probably
due to thrust-related major earthquakes. For example, the
1975.09.06 Lice earthquake (Ms: 6.7) was attributed to the
Bitlis Suture Zone (Arpat, 1977; Jackson and McKenzie,
1984). The Van Fault Zone was recognized and mapped
after the 2011.10.23 Van earthquake (Mw: 7.1) (Zahrandik
and Sokos, 2011), which taught us that blind thrusts are
important seismic sources in eastern/southeastern Turkey
and that they need to be studied in detail.
Southeastern Turkey presents several thrusts/blind
thrusts that can be determined by using asymmetrical fold

axes (Suppe, 1983; Mitra, 1990; Suppe and Medwedeff,
1990). We interpret these structures, together with
their counterparts in northern Syria and Iraq, as having

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Figure 1. Neotectonics of southeastern Turkey, northern Syria, and northern Iraq. Digital elevation model is obtained from the SRTM
3 arc-second data. Black lines are active structures outside of the SEAW. Red solid lines with triangles on the hanging wall are thrust
faults; dotted dashed lines represent the blind thrusts. Normal faults are shown by a rectangle on the hanging wall. Strike–slip faults
are shown with half arrows. Plio-Quaternary/Quaternary deposits are shown by the gray areas adapted from Günay and Şenel (2002),
Turhan et al. (2002), Ulu (2002), Şenel and Ercan (2002), Tarhan (2002), Krasheninnikov (2005), and ASGA-UNESCO (1963). DSFZ:
Dead Sea Fault Zone (Hall et al., 2005; Krasheninnikov et al., 2005), EAFZ: East Anatolian Fault Zone, NAFZ: North Anatolian Fault
Zone (Şaroğlu et al., 1992). BZSZ: Bitlis Zagros Suture Zone (Emre et al., 2013). I- Yavuzeli Blind Thrust Fault (YBT); II- Araban Blind
Thrust Fault (ABT); III- Çakırhüyük Blind Thrust Fault (ÇBT); IV- Halfeti Fault (HF); V- Adıyaman Thrust Zone (ATZ); VI- North
Karacadağ Fault (NKF); VII- Karacadağ Extensional Fissure (KEF); VIII- South Karacadağ Fault (SKF); IX- Mardin Blind Thrust Zone
(MBTZ); X- Ergani–Silvan Blind Thrust Fault (EBT); XI- Raman Thrust Fault (RTF); XII- Garzan Thrust Fault (GTF); XIII- Cizre
Thrust Fault (CTF); XIV- Silopi Blind Thrust Fault (SBT); XV- Bikhayr Blind Thrust Zone (BBTZ); XVI- Sincar–Kerkük Blind Thrust
Zone (SBTZ); XVII- Muş Thrust Fault (MTF); XVIII- Van Thrust Fault (VTF); XIX- Bozova Fault (BOF). XX- Başkale Fault (BKF);
XXI- Şemdinli–Yüksekova Fault (ŞYF); AG- Akçakale–Harran Graben; N-S: Location of regional cross section; B-B’: Magnetotelluric
data location of Türkoğlu et al. (2008). The western continuation of XVI (SBTZ) is drawn according to subsurface data presented in
Litak et al. (1997- Figure 14).

developed in the Southeast Anatolian Wedge (SEAW).
The cross-sectional geometry is very similar to that of a
tectonic wedge occurring in accretionary prisms above
subduction zones (Figure 2). The tectonic wedges mimic
a wedge-shape pile of snow in front of a snowplow. The

shape of the wedge is related to (1) the applied force, (2)
the friction on the basal thrust, (3) the internal strength
of the material in the wedge, and (4) the erosion of the
surface of the wedge (see Dahlen, 1990 for a review).
In this paper, we aim to contribute to the understanding
of the SEAW. We particularly examine major asymmetrical
folds in the region using Google Earth images, because
they would indicate the location of thrust/blind thrust
faulting. All these structures will provide information

106

about the internal structure of the SEAW that may
supply logical explanations for the thrust-related seismic
activity recorded in the instrumental period, such as the
1975.09.06 (M:6.7) Lice and 2012.06.14 (M:5.5) Şırnak–
Silopi earthquakes.
2. The structure of the SEAW in the Arabian foreland
The SEAW is located between the Bitlis–Zagros Suture
Zone (BZSZ) and Sincar Mountain in Iraq (Figure 1). Its
southern tip is represented by the Sincar–Kerkük Blind
Thrust Zone (SBTZ). The SEAW is mainly composed of
several thrust/blind thrust faults and related folds with
some strike–slip faulting. The reverse and/or thrust faults
that reach the surface are marked by continuous red lines


SEYİTOĞLU et al. / Turkish J Earth Sci

Figure 2. Tectonic wedge geometry (after Dahlen, 1990).


with triangles on the upthrust (hanging wall) side in the
maps presented in this paper. The red broken dotted lines
represent the approximate surface trace of blind thrusts
that is located in front of the forelimb. An asymmetrical
fold is determined by the short or long drainage system
together with the blunt or sharp “v” of bedding traces in
the Google Images (Figure 3).
Quaternary deposits unconformably cover various
earlier lithostratigraphical units including an Upper
Miocene unit containing mammalian fossils (Kaya et al.,
2012) in SE Turkey.
The internal structure of the SEAW is explained below,
from west to east.
Gaziantep area: to the NNW of the city of Gaziantep,
three prominent E–W trending plains are distinguished,
namely the Yavuzeli, Araban, and Çakırhüyük plains
(Figure 4a). The linear E–W trending northern border of
the Yavuzeli plain separates Quaternary deposits in the
south and Miocene limestones in the north (Ulu, 2002).
Two different drainage systems are recognized on the
limestones: south flowing drainages are shorter than the
north flowing one (Figures 4a–4c). This feature indicates
an asymmetrical anticline that may be related to a blind
thrust (Figure 4d). A similar blind thrust is reported
further to the south, just north of Kilis (Coşkun and
Coşkun, 2000). For this reason, identical structures are

expected on the north of the Araban and Çakırhüyük
plains (Figure 4a–4e). They are bounded from the west

by the NE–SW trending left lateral East Anatolian Fault
Zone and in the east the left lateral Halfeti Fault cuts
asymmetrical anticlines (Figure 4a).
The Adıyaman Thrust Zone (ATZ) is located to the
north of the Halfeti Fault (Figures 5a and 5b). The Eocene
units on the north thrust over Plio-Quaternary deposits
(Ulu, 2002) on the south along with ATZ via Narince. The
Halof dağı asymmetric anticline is located on the hanging
wall of the ATZ, as shown on the geological cross section
of Sungurlu (1974) (Figure 5c). The limbs of the Halof
dağı asymmetric anticline are clearly seen in Google Earth
images, where the anticline is seen to be partly eroded in
Pınaryayla (Figure 5d). Their control of the topography
of the region indicates that the ATZ and north dipping
normal faults must be young structures (Figure 5e).
West of Diyarbakır: to the east of Narince, between the
villages of Ceylan and Yayıklı, a branch of active faulting
is separated from the ATZ. This NW–SE trending right
lateral North Karacadağ Fault (NKF) (Emre et al., 2012)
is connected to the N–S trending Karacadağ Extensional
Fissure (KEF) (Şengör et al., 1985; Şaroğlu and Emre,
1987). We suggest that the KEF might be connected to the
Mardin Blind Thrust Zone (see next section) by a NW–SE
trending right lateral strike–slip South Karacadağ Fault

Figure 3. Blind thrust and fault-propagation fold with morphological features.

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Figure 4. (a) Neotectonic structures on the north of Gaziantep. See Figure 1 for the location. Plio-Quaternary/Quaternary deposits
are shown by the dark gray/gray areas respectively and adapted from Ulu (2002). Topography is obtained from the SRTM 3 arcsecond data. Dotted line represents the basal thrust of the SEAW. Broken dotted lines are the surface trace of blind thrusts. EAFZ:
East Anatolian Fault Zone; ÇBT: Çakırhüyük Blind Thrust Fault; ÇP: Çakırhüyük Plain; ABT: Araban Blind Thrust Fault; AP:
Araban Plain; YBT: Yavuzeli Blind Thrust Fault; YP: Yavuzeli Plain; HF: Halfeti Fault. (b) Typical drainage pattern on the hanging
wall of YBT. (c) Google Earth image of the hanging wall of YBT. South dipping beds (orange lines) of Miocene limestones and a
sharp contact with the Quaternary Yavuzeli Plain. (d) The cross section of Y-Y’ indicating asymmetrical anticline on the hanging
wall of YBT. (e) Z-Z’ topographical cross section of Çukurhüyük, Araban, and Yavuzeli plains and interpretation of the blind
thrusts.

(SKF) (Figure 6). The overall structure of the KEF is a
releasing bend between the NW–SE trending right lateral
strike–slip North and South Karacadağ faults that play the
role of a tear fault between the ATZ and the Mardin Blind
Thrust Zone (Figure 6). While the NKF and KEF may be
clearly followed on the topography and are mapped as
Quaternary faults (Emre et al., 2012), the trace of the SKF
corresponds to the locations of the parasitic cones of the
Karacadağ volcano (Figure 6) that is drawn as a continuous
right lateral fault by using information from the shorter
strike–slip segment on the geological map given by Turhan
et al. (2002).
Mardin area: the Mardin Blind Thrust Zone (MBTZ)
can be drawn by following the asymmetrical anticline axes

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in the region. The high angle southern limbs of the anticline
are limited by Quaternary and/or Plio-Quaternary deposits

(Turhan et al., 2002) (Figures 7a and 7b). A close-up view
around the city of Mardin indicates that the city is located
on the axis of a south verging asymmetrical anticline.
Cretaceous neritic limestone is exposed in the core of this
anticline. The Eocene limestones have steep dipping beds
towards the south and are limited by the Quaternary fill of
the Mesopotamian plain (Turhan et al., 2002) (Figure 7c).
The axes of these asymmetrical anticlines are en echelon in
nature that might be the reflection of several splays of the
MBTZ (Figures 7a and 8a). The MBTZ was shown on the
maps given by Lovelock (1984) and Perinçek et al. (1987)
and in the cross section reported by Krasheninnikov


SEYİTOĞLU et al. / Turkish J Earth Sci

Figure 5. (a and b) The Adıyaman Thrust Zone (ATZ) between Adıyaman and Narince. For location see Figure 1. EAFZ: East
Anatolian Fault Zone; BZSZ: Bitlis Zagros Suture Zone. Plio-Quaternary/Quaternary deposits are shown by the dark gray/gray
areas respectively and adapted from Ulu (2002), Tarhan (2002), and Turhan et al. (2002). Topography is obtained from the
SRTM 3 arc-second data. (c) D-D’ geological cross section across the Adıyaman Thrust Zone (ATZ). Modified and simplified
from Sungurlu (1974). (d) Cross-sectional view of Halof Dağı asymmetrical anticline, Google Earth image looking east near
Pınaryayla. (e) X-X’ topographical cross section of Halof Dağı and relationship between asymmetric anticline and ATZ.

(2005). The E–W trending MBTZ bends to the NE–SW
between Nusaybin and İdil (Figure 8a) and continues
to the west of Cizre. This zone can be traced along the
border of the S and SE dipping Eocene limestone unit and
the Quaternary deposits of the Mesopotamian plain but
it cannot be followed further NE due to the Quaternary
basalt lava flow around İdil (Turhan et al., 2002) (Figure

8a).
North of MBTZ: to the north of Mardin, the Raman
Thrust Fault (RTF) is shown on geological maps (Turhan
et al., 2002; Yıldırım and Karadoğan 2011) and on the
cross section reported by Lovelock (1984). There is a
major asymmetrical fold axis on its hanging wall at Raman
Dağı (Figures 8a–8c). The steeply dipping southern limb
and shallow dipping northern limb are clearly seen on the

Google Earth images (Figures 8b and 8c). The Pleistocene
uplift of the structure, due to the RTF, is represented by
three different alluvial terraces seen only on the northern
slopes of the Dicle river north of Hasankeyf (Yıldırım and
Karadoğan, 2005) (Figure 8b).
Further to the north, the NW–SE trending Garzan
Thrust Fault (GTF) is responsible for the formation of
the Garzan asymmetric anticline (Figures 8d and 8e). The
anticline axis and thrust fault are nearly parallel to each
other, lying N 65 W. The northern limb of the anticline
dips 15° while the southern limb has a steeper dipping,
slanting up to 75°, and is locally overturned (Sanlav et al.,
1963; Ketin, 1983). The thrust fault dips 55° towards the
NE and has a 600 m vertical throw (based on correlation
of wells 43 and 47) that dies out towards the NW and SE

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Figure 6. NW–SE trending North Karacadağ (NKF) and South Karacadağ (SKF) faults and the position of Karacadağ Extensional
Fissure (KEF) as a releasing bend. See Figure 1 for location. Circles are the locations of parasitic cones of the Karacadağ volcano.
Plio-Quaternary/Quaternary deposits are shown by the dark gray/gray areas respectively and adapted from Turhan et al. (2002)
and Tarhan (2002). Topography is obtained from the SRTM 3 arc-second data.

(Sanlav et al., 1963) (Figure 8f). Further to the SE, in front
of its steeply dipping limbs, well developed Quaternary
deposits (Turhan et al., 2002) demonstrate that this is a
neotectonic structure.
Another prominent structure is the Ergani–Silvan
Blind Trust Fault (EBT) determined by the south dipping
beds that can be seen on Google Earth images. The axis
of the asymmetric anticline is parallel to the thrust zone,
which limits the Quaternary deposits particularly to the
south of Ergani (Tarhan, 2002) (Figure 9a). This thrust
zone is also the best source candidate for the 1975.09.06
(Ms: 6.7) Lice earthquake (see below).
The EBT was recognized by Gilmour and Makel (1996)
in whose study the EBT and related fault-propagation
folds were clearly seen in seismic reflection sections. The
Hazro asymmetric anticline is located on the hanging wall
of the EBT (Figures 9a–9c). The axis of the Hazro anticline
is eroded and the Silurian beds are exposed (Ketin, 1983)
(Figure 9b).
The Cizre–Silopi area: the WNW–ESE trending Cizre
Thrust Fault (CTF) is shown on the MTA’s active fault map
(Duman et al., 2012) and continues toward northern Iraq
(Figure 10a). The CTF separates into a middle Triassic–
Upper Cretaceous Cudi Group and lower–middle Eocene
units (Schmidt, 1964). In the hanging wall of the thrust,

the Cudi group creates an asymmetric anticline and the
footwall is composed of nearly vertical or overturned

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Eocene units (Figure 10b). To the NE of Silopi, the tilted
Miocene beddings are in contact with Quaternary alluvial
fan deposits (Günay and Şenel, 2002) that indicate the
Silopi Blind Thrust Fault (SBT) and this structure continues
to the east towards Derker Ajam (northern Iraq) (Figure
10a). Further south, the anticline at the Bikhayr mountains
(Ameen, 1991) in the south of Zaho (Iraq) and south of
Al-Malikiyah (Syria) indicates another blind thrust zone
named the Bikhayr Blind Thrust Zone (BBTZ). This can be
traced from Tepke (Syria) (Kent, 2010) to Dohuk (Iraq) via
Dayrabun (Iraq). No certain relationship between these
structures has been established by using Google Earth
images but the BBTZ, the MBTZ, and the CTF overlap
each other around Al-Malikiyah and İdil (Figure 10a). All
the structures in the Cizre–Silopi area are assumed to be
connected by a basal thrust and their relationships with
each other and with the topography are shown in Figure
10c.
The Sincar and Abdülaziz Mountains: Sincar Mountain
in Iraq is located 92 km south of the Mardin Blind Thrust
Zone (Figures 1 and 11a). The overall structure of Sincar
Mountain is a closed anticline, but a more detailed look
reveals that it has a small syncline on the axis of a huge
anticline (Figure 11b). The drainage pattern and shape of
V’s of the bedding in both limbs of the anticline indicate

that the northern limb has a higher dip value than the
southern limb (see also the subsurface data reported by


SEYİTOĞLU et al. / Turkish J Earth Sci

Figure 7. (a) Mardin Blind Thrust Zone (MBTZ) having several segments. Broken dotted lines are the surface trace of the blind
thrust. Plio-Quaternary/Quaternary deposits are shown by the dark gray/gray areas respectively and adapted from Turhan et al.
(2002). Topography is obtained from the SRTM 3 arc-second data. (b) Google Earth image immediately south of Mardin. Rule
of V’s indicates south dipping beds (orange lines) and sharp contact with the Plio-Quaternary deposits (c) W-W’ topographical
cross section of Mardin area and simplified asymmetric anticline and its relationship with the interpreted blind thrusting.

Brew et al., 1999), which is dissimilar to the dip features
of the anticlines in southeast Turkey; this is probably
due to back thrusting under the northern limb of the
Sincar anticline (Figure 11c). We evaluate that the Sincar
anticline was created by the Sincar–Kerkük Blind Thrust
Zone (SBTZ), representing the southernmost tip of the
SEAW. This is followed towards the south of Musul via
Tel Afer to the east (Kent, 2010) and towards Abdülaziz
Mountain to the west (Figure 1). Abdülaziz Mountain has
a similar, but less prominent, structure (Sawaf et al., 1993;
Kent and Hickman, 1997; Rukieh et al., 2005) to Sincar
Mountain (Brew et al., 1999; 2001). The northern margin
of Abdülaziz Mountain is limited by a south dipping thrust
fault (Sawaf et al., 1993; Kent and Hickman, 1997; Kazmin,
2005) that can be interpreted as a back thrusting similar
to that of Sincar Mountain. The geomorphological map
of Syria compiled by K Mirzayev (Krasheninnikov, 2005)
indicates that Abdülaziz Mountain is surrounded by upper

Quaternary and recent alluvial fans.

The western edge of Abdülaziz Mountain is probably
connected to the Akçakale–Harran graben, with strike–
slip faulting (the Abba fault of Lovelock, 1984) that is
subparallel to the Bozova Fault (BOF). In this case, it is
interesting to see that a more evolved and similar structure
developed with the NKF, the KEF, and the SKF (Figure 1).
All the observations explained above demonstrate that
there is the SEAW in front of the BZSZ and its southern tip
is located in the Sincar–Kerkük Blind Thrust Zone.
3. Morphometric analysis (mountain front sinuosity)
In order to evaluate the tectonic activity along thrust/blind
thrust faults, mountain front sinuosity (Smf ) values were
determined as morphometric analysis (Figure 12). Smf is
defined as
Smf = Lmf/Ls,
where Lmf is the length of the mountain front along the mountain
range–basin boundary and Ls is the straight-line length of the
same front (Figure 12a) (Bull and McFadden, 1977).

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Figure 8. (a) Eastern continuation of the Mardin Blind Thrust Zone (MBTZ) and the positions of Cizre Thrust Fault (CTF), Raman Thrust Fault (RTF), and
Garzan Thrust Fault (GTF). For location see Figure 1. Broken dotted lines represent the surface trace of the blind thrusts. Plio-Quaternary/Quaternary deposits are
shown by the dark gray/gray areas and adapted from Turhan et al. (2002), Günay and Şenel (2002), and Tarhan (2002). Topography is obtained from the SRTM 3
arc-second data. (b) The detail of Raman Thrust Fault at the north of Hasankeyf. The traces of bedding (orange lines) on the Google Earth image indicate Raman

asymmetric anticline. The terraces located on the northern slopes of Dicle River (oldest -T1: 60–80 m, T2: 30–50 m, youngest -T3: 8–10 m from the valley floor) are
adapted from Yıldırım and Karadoğan (2005). (c) The relationship asymmetric Raman anticline and Raman Thrust Fault on the V-V’ topographical cross section.
(d) Close up Google Earth image of Garzan Thrust Fault. (e) The traces of bedding (orange lines) indicate asymmetrical anticline on the Google Earth image
according to rule of V’s. (f) C-C’ geological cross section across the GTF (after Sanlav, 1963; Ketin, 1983).

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Figure 9. (a) Map of Ergani–Silvan Blind Thrust (EBT). Eastern part of the EBT is adapted from Gilmour and Makel (1996).
See Figure 1 for location. Broken dotted line represents the surface trace of the blind thrusts. Plio-Quaternary/Quaternary
deposits are shown by the dark gray/gray areas and adapted from Turhan et al. (2002) and Tarhan (2002). Topography is
obtained from the SRTM 3 arc-second data. (b) Geological cross section of Hazro asymmetric anticline (Ketin, 1983). (c)
Relationship between Hazro asymmetric anticline and Ergani–Silvan Blind Thrust Fault.

Mountain front sinuosity is related to erosional
processes and tectonic activity. Tectonically active fronts
generally have straight mountain range–piedmont (basin)
junctions. Smf values lower than 1.4 indicate high tectonic
activity (Rockwell et al., 1984; Keller, 1986).
In the present study, we performed Smf analysis on the
mountain fronts that are related to the thrust/blind thrust
fault segments (Figures 12b–12m). The analysis shows
that the Smf values of most of the segments are lower than
1.4 (Figure 12n). This result indicates that the faults are
tectonically active in the region supported by the thrustrelated seismic activity (see next section and Table), where
the GPS results show 17.8 ± 1.1 mm/year contraction
(Reilinger et al., 2006). Only some parts of the MBTZ have
values higher than 1.4 and these segments can accordingly

be evaluated as tectonically less active (Figure 12k).

4. Seismotectonics of southeastern Turkey, northern
Syria, and Iraq
The epicenter distribution of the earthquakes from the
Boğaziçi University Kandilli Observatory and Earthquake
Research Institute (KOERI, 1900–2015) strongly
documents some clusters in the region (Figure 13). It can
easily be recognized that the left-lateral strike–slip East
Anatolian Fault Zone (EAFZ) and the right-lateral North
Anatolian Fault Zone (NAFZ) are the main sources of
earthquake occurrences in the region.
The second important earthquake cluster in the area
is related to the 2011.10.23 Van earthquake (Mw: 7.1),
which was created by a blind thrust (see below). It is
important to note that until this recent Van earthquake,
only the 1975.09.06 Lice earthquake (Ms: 6.7) was known
as a major event related to thrust faulting in the region.

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Figure 10. (a) Map of the Cizre Thrust Fault (CTF), the Silopi Blind Thrust Fault (SBT), the Bikhayr Blind Thrust Zone (BBTZ), and
the eastern end of Mardin Blind Thrust Zone (MBTZ). For location see Figure 1. Broken dotted lines are the surface trace of the blind
thrusts. Plio-Quaternary/Quaternary deposits are shown by the dark gray/gray areas and adapted from Günay and Şenel (2002) and
Turhan et al. (2002). Topography is obtained from the SRTM 3 arc-second data. (b) Geological cross section across the CTF (Schmidt,
1964). (c) T-T’ topographical cross section and relative positions of the CTF, the SBT, and the BBTZ. Dotted line represents the basal
thrust of the SEAW.


For this reason, Ambraseys (1989) refers to the existence
of a quiescent period during the 20th century. Before the
2011 Van earthquake, seismicity data give an impression
that right- and left-lateral strike–slip faults produced most
of the earthquakes in the south of the BZSZ (Figure 13).
The third earthquake cluster is related to the right lateral
Bozova Fault and the marginal faults of the Akçakale/
Harran Graben, the forth seismic intensity seems to be
related to the dextral Yüksekova–Şemdinli Fault, and the
fifth seismic intensity can be recognized around Silopi.
The 2012.06.14 Şırnak–Silopi earthquake (Mw: 5.1) (see
below) indicates that the E–W thrusting (Bikhayr Blind
Thrust Zone) is also a major neotectonic structure capable
of producing major seismic events (Figure 13).

114

In the NE of Syria, the sixth seismic cluster of moderate
earthquakes is located around Haseki. This cluster is
probably related to a NW–SE trending right-lateral tear
fault in the Sincar–Kerkük Blind Thrust Zone. It should
be noted that our evaluation contradicts the interpretation
given by Abdul-Wahed and Al-Tahhan (2010), whose
study suggested E–W trending left-lateral strike–slip
faulting in this region.
The focal depths of all catalog events (from 1900 to
2015) for this region indicate that generally most of the
events occurred in the crust (upper 30 km). However, we
observe that there are several deep earthquakes located as

far down as 170 km. Their quantity is very low relative to
the crustal events. Especially after the year 2000, which saw


SEYİTOĞLU et al. / Turkish J Earth Sci

Figure 11. (a) Location of the Sincar–Kerkük Blind Thrust Zone (SBTZ). See Figure 1 for the location. Broken dotted lines are
the surface trace of the blind thrusts. Quaternary deposits are shown by the gray areas and adapted from ASGA-UNESCO (1963).
Topography is obtained from the SRTM 3 arc-second data. (b) Cross-sectional view of Google Earth image of Sincar Mountain.
Looking east. Note a small syncline on the top of the mountain. (c) Topographical cross section of Sincar Mountain and the
relationship between anticline structure and thrusting (after Brew et al., 1999).

the start of the Turkish national seismic network expansion
studies, the rate of such deeper events is gradually reduced;
this is due to increased quality and quantity of observation.
To be able to interpret the internal structure of the
SEAW, many focal mechanism solutions referring to
selected earthquakes were either calculated or collected
from several catalogs and publications. A full data set is
presented in the Table.
We calculated the focal mechanism solutions for
selected events in the region (Figure 13; Table). We selected
magnitudes (ML) of the events varying in a range between
3.4 and 4.9. These events occurred between 2004 and 2015.
They were firstly relocated and then their source parameters
were calculated by using a moment tensor inversion
method. Therefore we processed the time domain regional
moment tensor inversion following Herrmann et al. (2011)
in order to obtain the source depth, moment magnitude
and strike, and dip and rake angles of a shear-dislocation

source, using three-component broadband waveforms.

The waveform data pole-zero files were retrieved from the
KOERI data archive. The main idea in this method is to
fit synthetic waveforms to observed seismograms at local
and regional stations. The synthetic Green’s functions were
computed as suggested in Herrmann et al. (2011). Both
the observed and Green’s function ground velocities were
cut from a range of 5–10 s before the P-wave’s first-arrival
to a range of 110–180 s after it. In the inversion process
a three-pole causal Butterworth bandpass filter changing
with a 0.02–0.11 Hz band range was used for the events.
Additionally, an optional microseism rejection filter was
applied to enhance the signal-to-noise ratio when needed.
We eliminated noisy and problematic signals; furthermore,
waveform data recorded by stations beyond 700 km were
deselected. After the moment tensor inversion process, we
determined the source parameters of 28 events. They are
given in the Table and shown in Figure 13.
The overall epicentral distributions and available focal
mechanism solutions of the earthquakes demonstrate that

115


SEYİTOĞLU et al. / Turkish J Earth Sci

Figure 12. Mountain front sinuosity related to the thrusts/blind thrusts. (a) Definition of Smf (Bull and McFadden, 1977). (b)
Yavuzeli Blind Thrust (YBT). (c) Araban Blind Thrust (ABT). (d) Çakırhüyük Blind Thrust (ÇBT). (e–f) Mardin Blind Thrust
Zone (MBTZ). (g) Ergani–Silvan Blind Thrust (EBT). (h) Bikhayr Blind Thrust Zone (BBTZ). (i) Silopi Blind Thrust (SBT). (j)

Sincar–Kerkük Blind Thrust Zone (SBTZ). (k) Adıyaman Thrust Zone (ATZ). (l) Raman Thrust Fault (RTF) and Garzan Thrust
Fault (GTF). (m) Cizre Thrust Zone (CTZ). (n) Tectonic activity values of the faults.

E–W trending thrusts and NW–SE trending right-lateral
and NE–SW trending left-lateral strike–slip faulting are
active structures in the region.
4.1. Major thrust-related earthquakes in E and SE Turkey
In order to understand the internal structure of the SEAW,
it would be useful to closely examine thrust-related
earthquakes. The first Van earthquake, which is located
outside of SEAW, is reviewed; then the thrust-related Lice
and Şırnak–Silopi earthquakes inside the SEAW will be
examined.
2011.10.23 (Mw: 7.1) Van earthquake
Field reports (Akyüz et al., 2011; Emre et al., 2011;
Erdik et al., 2012) and seismological reports (Zahrandik
and Sokos, 2011) that followed the 2011.10.23 Van
Earthquake confirm that the source of the earthquake is
a north dipping thrust fault. Some researchers conclude
that the fault responsible for the 2011.10.23 Van
earthquake (Mw: 7.1) is a blind fault, and related to this

116

surface deformations can be seen in the north of the city
of Van (Özkaymak et al., 2011; Akyüz et al., 2011; Emre
et al., 2011; Doğan and Karakaş, 2013). Although most
observers agree on the source of the fault, which has been
given different names (the Van Fault, the Bardakçı–Saray
Thrust Fault, the Everek Reverse Fault), Koçyiğit (2013) is

opposed to the blind fault evaluation and concludes that
all major aftershocks were produced by separate individual
faults in the region.
1975.09.06 (Ms: 6.7) Lice earthquake
Arpat (1977) presented detailed field observations and
concluded that the 1975 Lice earthquake was related to
reverse faulting, evidenced by the ground cracks (17–19
cm), left lateral displacements (13–14 cm), and the 60-cm
up-throw of the surface along a distance of 300 m. The
deformations were mapped around the village of Yünlüce
in the Miocene Lice Formation; this formation is the
autochthonous unit in the footwall of a major thrust fault


16:32:51:0 37.75

16:44:11:0 37.80

1996/01/04

1996/01/11

1996/07/09

2000/11/15

2004/10/05

2005/01/25


4

5

6

7

8

9

10 2005/01/25

00:17:38:0 36.84

15:05:37.0 38.41

21:49:22.1 36.56

23:03:36.2 36.55

15:28:07.3 36.64

14:35:46.8 36.33

43.48

43.51


41.25

42.95

39.34

40.62

40.79

39.80

0.2

0.3

5

48

3.8

3.8

2.5

3.8

10


4.9

4.5

3.4

5.4

4.8

4.6

4.7

4.3

6.7

ML

ML

ML

Ms

ML

ML


ML

ML

Ms

Ms

1995/04/22

40.72

6.5

45

45

Abdul-Wahed
and Al-Tahhan 161
(2010)
Abdul-Wahed
and Al-Tahhan 146
(2010)

This Study

This Study

This Study


125

60

307

90

85

81

64

50

Abdul-Wahed
and Al-Tahhan 161
(2010)

100

45

Abdul-Wahed
and Al-Tahhan 141
(2010)

ISC


54

244

Jackson and
McKenzie
(1984)

64

304

KOERI

-170

10

160

111

-170

-180

-175

-175


54

147

Dip1 Rake1
(°)
(°)

3

09:20:11.0 38.47

26

Reference

1975/09/06

41.56

MTyp

2

12:22:10.5 39.17

Mag.

1966/08/19


Depth
(km)

1

Lon.
(°E)

Str1
(°)

Lat.
(°N)

Date
(y/m/d)

#

Time
(GMT)

Fault plane parameters

Earthquake parameters

35

329


40

239

51

71

66

46

114

50

Str2
(°)

80

80

70

33

85


90

85

85

50

61

Dip2
(°)

Table. Earthquake parameters and focal mechanism solutions of the major seismic events in the research area.

0

175

10

54

-45

-45

-50

-50


128

30

Rake2
(°)

350

194

355

175

357

16

17

353

359

358

Pazm
(°)


7

3

7

17

36

30

30

33

3

2

Pplg
(°)

260

285

262


46

106

126

122

103

94

266

7

11

21

65

24

30

24

27


62

41

Tazm Tplg
(°)
(°)

This Study

This Study

This Study

Tan (2004)

Abdul-Wahed
and Al-Tahhan
(2010)

Abdul-Wahed
and Al-Tahhan
(2010)

Abdul-Wahed
and Al-Tahhan
(2010)

Abdul-Wahed
and Al-Tahhan

(2010)

Jackson and
McKenzie
(1984)

McKenzie
(1972)

Reference

Beach Ball

SEYİTOĞLU et al. / Turkish J Earth Sci

117


118

17:11:02:0 37.92

17:15:13:0 38.01

17:52:13:0 37.93

00:04:51:0 38.60

11:16:19:0 37.74


12:22:28:0 37.61

15:11:52:0 37.69

01:23:27:0 37.75

13:05:14:0 37.76

21:41:03:0 36.98

02:56:00:0 37.65

11 2005/01/25

12 2005/01/25

13 2005/01/25

14 2005/01/26

15 2005/01/26

16 2005/01/26

17 2005/01/26

18 2005/01/27

19 2005/01/29


20 2005/05/29

21 2006/05/21

Table. (Continued).

43.61

42.05

43.76

43.68

43.54

44.25

43.79

44.19

43.32

43.46

44.41

6.9


3.1

9.9

6.8

2.5

13.5

5.4

9.3

0.1

1.9

14

3.9

4.3

3.9

4.1

4


4

4.1

4.1

4.3

4.1

4.4

ML

ML

ML

ML

ML

ML

ML

ML

ML


ML

ML

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

194

272


300

115

207

180

120

170

41

143

92

77

66

90

90

80

55


90

75

76

54

74

128

123

-15

10

165

-50

-155

45

164

127


-143

300

35

30

25

300

304

30

65

135

270

350

40

40

75


80

75

51

65

47

75

50

55

20

40

-180

180

10

-133

0


159

15

50

-20

256

339

254

250

254

149

348

292

88

207

316


23

14

11

7

4

58

17

17

0

2

37

142

226

346

340


163

243

252

38

358

113

217

44

56

11

7

18

2

17

42


21

60

12

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

SEYİTOĞLU et al. / Turkish J Earth Sci



10:21:24:0 37.58

08:12:36:0 37.28

22:50:53:0 37.67

09:08:57:0 37.27

23:19:57:0 37.17

20:53:22:0 36.18

13:13:02:0 37.26

10:41:21.0 38.779 43.351 15

03:17:04:0 38.4983 40.7248 5.4

25 2007/09/22

26 2007/09/24

27 2007/11/09

28 2008/05/11

29 2009/03/01

30 2009/03/10


31 2011/10/23

32 2012/04/28

43.56

42.32

43.32

44.38

43.84

42.93

43.97

5

3.7

5.4

8.7

3.6

16


0.6

5

24 2007/09/21

41.09

13:56:25:0 36.50

9.8

23 2006/11/16

42.6

03:48:34:0 37.91

22 2006/05/21

Table. (Continued).

4.7

7.1

4.3

4.3


4.3

4.2

4

4.4

4.5

4.2

4.9

ML

Mw

ML

ML

ML

ML

ML

ML


ML

ML

ML

318

236

Zahradnik
and Sokos
(2011)

This Study

164

129

145

190

104

191

255


136

200

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

This Study

69

46

86

85


90

55

76

60

80

85

85

131

70

-135

170

-155

-50

-164

145


-55

-170

-50

70

84

70

220

55

314

10

300

359

45

296

45


48

45

80

65

51

75

60

36

80

40

30

110

-5

5

0


-133

-15

35

-163

-5

-172

19

160

37

175

13

159

327

245

199


1

145

14

1

33

4

17

58

21

0

44

11

37

272

67


288

84

277

253

237

155

318

270

259

49

76

27

11

17

2


0

45

27

4

29

This Study

Zahradnik
and Sokos (2011)

This Study

This Study

This Study

This Study

This Study

This Study

This Study


This Study

This Study

SEYİTOĞLU et al. / Turkish J Earth Sci

119


120

08:22:15:0 38.85

21:34:59:0 36.8215 42.2828 5

07:59:39:0 37.2875 38.644 5

35 2014/09/28

36 2014/12/23

37 2015/11/10

41.00

5

18.9

01:10:27:0 36.49


34 2013/08/02

43.48

05:52:51.0 37.1572 42.4437 11.68

33 2012/06/14

Table. (Continued).

3.6

4.1

4

4.5

5.1

ML

ML

ML

ML

Mw


This Study

This Study

This Study

This Study

AFAD

35

120

301

309

333

75

76

76

66

52


-40

159

164

108

141

137

215

35

90

90

52

70

75

30

60


-161

15

15

55

45

349

168

348

25

210

38

4

0

19

5


91

76

258

250

306

15

24

21

64

52

This Study

This Study

This Study

This Study

AFAD


SEYİTOĞLU et al. / Turkish J Earth Sci


SEYİTOĞLU et al. / Turkish J Earth Sci

Figure 13. Earthquake activity of southeastern Turkey, northern Syria, and Iraq between 1900 and 2015. Earthquake
epicenter data (purple dots) are provided by the Boğaziçi University Kandilli Observatory and Earthquake Research Institute
(KOERI). Digital elevation model is obtained from the SRTM 3 arc-second data. Black lines are active structures outside
of the SEAW. Red solid lines with triangles on the hanging wall are thrust faults; dotted dashed lines represent the blind
thrusts. Normal faults are shown by a rectangle on the hanging wall. Strike–slip faults are shown with half arrows. Red focal
mechanism solutions are from different sources (see Table for references). Black focal mechanism solutions are produced
in this study. See Table for details. N-S cross section in which earthquake data inside the dotted area are plotted. NAFZ:
North Anatolian Fault Zone, EAFZ: East Anatolian Fault Zone, BZSZ: Bitlis–Zagros Suture Zone, XVIII: Van Thrust Fault,
XIX: Bozova Fault, AG: Akçakale–Harran Graben, XXI: Şemdinli–Yüksekova Fault, XV: Bikhayr Blind Thrust Zone, XVI:
Sincar–Kerkük Blind Thrust Zone.

representing the BZSZ (Arpat, 1977). The focal mechanism
solution of the 1975.09.06 Lice earthquake indicates a 54°
NW dipping fault surface at 10-km depth (Jackson and
McKenzie, 1984). This requires a distant surface rupture
around 7 km south of the epicenter. The reverse faults
mapped by Arpat (1977) after the 1975 earthquake are only
600 m south of the epicenter. For this reason, Arpat’s (1977)
observations should be evaluated as surface deformations
caused by the earthquake and they cannot be regarded as
a major surface break of the earthquake produced by a
regional thrust fault. If the depth and dip of fault values
(Jackson and McKenzie, 1984) are taken into account,
the thrust fault responsible for the 1975 Lice earthquake

should be traced at the surface south of the epicenter.
Interestingly, this location somewhat corresponds to the
newly determined the Ergani–Silvan Blind Thrust Fault (in
this paper) and this should then be evaluated as a possible
source of the 1975.09.06 Lice earthquake (Figure 14a).

2012.06.14 (Mw: 5.1) Şırnak–Silopi earthquake
According to the preliminary report by the Disaster
and Emergency Management Presidency of Turkey
(AFAD), the focal mechanism solution (based on P wave
first motion) of the Şırnak–Silopi earthquake (2012.06.14;
Mw: 5.1) indicates thrust faulting with a depth of 11.6 km
(AFAD, 2012a). While the foreshock (2012.06.14–05:50)
and main shock (2012.06.14–05:52) indicate thrusting, its
aftershock (2012.06.15–23:48) has a strike–slip character
(AFAD, 2012b). Neither the preliminary nor the monthly
AFAD reports provide the name of the faults responsible
for these seismic events. The information about location,
depth, and focal mechanism solutions suggests that the
fault responsible for the Şırnak–Silopi earthquake is the
Bikhayr Blind Thrust Fault (Figure 14b).
5. Discussion
Türkoğlu et al.’s (2008) magnetotelluric data point out
a low resistivity area in the south of the BZSZ and the
area’s thickness is reduced towards the south (Figures

121


SEYİTOĞLU et al. / Turkish J Earth Sci


Figure 14. (a) Relationship of the 1975.09.06 Lice Earthquake and the Ergani–Silvan Blind Thrust (EBT). (b)
Relationship between the 2012.06.14 Cizre-Silopi Earthquake and the Bikhayr Blind Thrust Zone (BBTZ).
BZSZ: Bitlis–Zagros Suture Zone, CTF: Cizre Thrust Fault, SBT: Silopi Blind Thrust.

15a and 15b). A regional cross section made with seismic
data indicates that the SEAW can be correlated with the
magnetotelluric data (Figure 15c).
After examining thrust-related earthquakes in the
region, it can be seen that north dipping thrust surfaces
have a range of dip angle of 46°–66°. These values are very
high for the basal thrust angle of a tectonic wedge when
they are compared to the low surface angle value of the
SEAW. For this reason, it can be speculated that seismic
activity occurs generally on the splays of faults separated
from the basal thrust (Figure 15c). The other explanation
for the absence of focal mechanism solutions showing low
angle thrust fault surfaces is the probable ductile shearing
on the basal thrust as suggested by Berberian (1995) for the
Zagros foreland. The seismic activity of the SEAW might be

122

triggered by both the northward movement of the Arabian
plate (Aktuğ et al., 2016) and the surface uplift of eastern
Anatolia due to asthenospheric cushioning (Şengör et al.,
2008) obeying the critical taper model of Dahlen (1990).
The nodal planes of the focal mechanism solutions
obtained from the thrust-related earthquakes (i.e.
1975.09.06 Lice and 2012.06.14 Şırnak–Silopi earthquakes)

are parallel to the regional asymmetrical anticline axes at
the surface. This pattern is an indication of active blind
thrust faults in the SEAW. The general linear morphology
between the asymmetric anticlines and Plio-Quaternary/
Quaternary deposits supports this argument. The lack
of detailed Quaternary stratigraphy and morphometric
analyses in the region prevents any assignment about
shortening and uplift rates across the SEAW.


SEYİTOĞLU et al. / Turkish J Earth Sci

Figure 15. (a) An enlarged magnetotelluric cross section by Türkoğlu et al. (2008) indicating that low resistivity areas have a wedge
shape. (b) The regional MT cross section from Türkoğlu et al. (2008). For location see Figure 1. (c) The regional topographic cross
section with earthquake hypocenter data (purple dots) indicating SEAW on the south of BZSZ. Please note the surface slope that is
identical with the ideal tectonic wedge shown in the Figure 2. (d) The overall structure of east and southeast of Anatolia. EAAC: East
Anatolian Accretionary Complex (Şengör et al., 2008), BM: Bitlis Massif (Oberhansli et al., 2010), SEAW: Southeast Anatolian Wedge
(this paper), BZSZ: Bitlis Zagros Suture Zone, XVII: Muş Thrust Fault, XII: Garzan Thrust Fault, XI: Raman Thrust Fault, XIII: Cizre
Thrust Fault, IX: Mardin Blind Thrust Fault, XVI: Sincar–Kerkük Blind Thrust Zone.

The overall and simplified structure shown by the map
view is composed of E–W trending thrusts and NW–SE
right lateral and NE–SW left-lateral strike–slip faulting.
The seismicity in the region demonstrates that all of
the structures mentioned above are active and working
together. The strike–slip faulting generally plays a role in
tear faulting. When releasing bend and releasing stepover
structures are developed along the strike–slip system,
the Karacadağ extensional fissure and Akçakale–Harran
graben locations fit these structures. This is one of the

important outcomes of the newly proposed neotectonic
framework of the region that explains every major
structure in the area, such as the position of the Sincar and

Abdülaziz mountains uplifting in the Mesopotamian plain
at the southern tip of the SEAW.
6. Conclusion
In the north of the BZSZ, the East Anatolian Accretionary
Complex has previously been determined (Şengör et al., 2003,
2008). After defining the SEAW in the south of the BZSZ
with this paper, the overall structure of east and southeast
Anatolia has emerged (Figure 15d). The internal structure
of the SEAW is composed of several fault-propagation folds
on the hanging wall of thrust/blind thrust faults, which is
similar to the Zagros foreland, and their relationship with
the Quaternary deposits has been demonstrated.

123


SEYİTOĞLU et al. / Turkish J Earth Sci
This paper provides a new neotectonic framework
for SE Turkey, northern Iraq, and Syria. This represents
a milestone in our developing understanding of the
relationship between the active structures and seismic
activity in the region, which was previously evaluated as
a simple fold belt, and where the structures observed in
these countries were not seen binding each other in the
previous studies.
Until the 2011.10.23 Van earthquake (Mw: 7.1) the

only known major thrust-related earthquake in the
instrumental period was the 1975.09.06 Lice earthquake
(Ms: 6.7), and earth scientists had a perception that the
deformation in SE Anatolia mainly accommodated with
strike–slip faulting. The Van earthquake teaches us that
blind thrusts are among the most important sources of
major earthquakes in the region. This paper demonstrates
that the internal structure of the SEAW contains many

thrusts/blind thrusts, some of which may be potential
sources of future earthquakes, as suggested in the cases
of the 1975.09.06 Lice and 2012.06.14 Şırnak–Silopi
earthquakes. Configuration of the fault lines in this paper
should be further analyzed in the field and the active
tectonic map of the region must be revised accordingly.
Acknowledgments
The first author wishes to thank Mark Brandon for several
discussions on the mechanism of the wedges during his
sabbatical leave (2011–2012) at Yale University, where
the main idea of this paper was propagated. Fruitful
discussions with Turkish Petroleum geologists Remzi
Aksu, Nuray Şahbaz, and Mert Türesin were also useful.
This paper benefited from the valuable comments of
Mustapha Meghraoui and an anonymous referee for which
we are grateful.

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