The neotectonics of southeast Turkey, northern Syria, and Iraq

22 Pages·2017·39.9 MB·English

Turkish Journal of Earth Sciences Turkish J Earth Sci
(2017) 26: 105-126
http://journals.tubitak.gov.tr/earth/ © TÜBİTAK
doi:10.3906/yer-1605-21
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 2
Gürol SEYİTOĞLU *, Korhan ESAT , Bülent KAYPAK
1
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 Perinçek et al., 1987; Gilmour and Makel, 1996) and only
The neotectonics of southeastern Turkey began after the the fold axes are shown on the maps (Şengör et al., 1985,
collision of Arabian and Eurasian plates along the Bitlis– 2008; Yılmaz, 1993; Okay, 2008). The Zagros foreland,
Zagros suture zone (Şengör, 1980; Şengör and Yılmaz, 1981; however, is relatively well studied in terms of blind
Şengör et al., 1985). The collision history starts during thrusting, seismicity, and GPS data (Berberian, 1995;
the Late Maastrichtian–Early Eocene and final contact of Hatzfeld et al., 2010; Agard et al., 2011) (Figure 1).
the continents and formation of the zone of imbrications The existing active fault map of Turkey (Emre et al.,
take place in Late Miocene times (Hall, 1976; Şengör and 2013) does not explain the correlation with all seismic
Kidd, 1979; Aktaş and Robertson, 1984; Yılmaz, 1993). events, especially in southeastern Turkey. Most of the active
Recently, Robertson et al. (2016) distinguished three faults are of a strike–slip nature and are recognized after
main tectonic phases in Southeastern Turkey: during the major earthquakes in eastern Turkey (i.e. Çaldıran, Varto,
Late Campanian, Early Eocene, and Early Miocene. The Bingöl). Active thrust fault lines are rare on the MTA map,
intracontinental convergence is also continuing in the with the exception of the Bitlis Suture Zone, and the Van
present day (Şengör and Kidd, 1979; Şaroğlu and Güner, and Cizre Faults, whose limited identification is probably
1981; Allen et al., 2004; Reilinger et al., 2006; Aktuğ et al., due to thrust-related major earthquakes. For example, the
2016). 1975.09.06 Lice earthquake (Ms: 6.7) was attributed to the
In contrast to the earlier evaluations of thick Bitlis Suture Zone (Arpat, 1977; Jackson and McKenzie,
continental crust (e.g., 55 km, Dewey et al., 1986), recent 1984). The Van Fault Zone was recognized and mapped
studies demonstrate that eastern Turkey has a 45-km- after the 2011.10.23 Van earthquake (Mw: 7.1) (Zahrandik
thick crust with an accretionary complex supported by and Sokos, 2011), which taught us that blind thrusts are
asthenospheric cushioning (Keskin, 2003; Şengör et al., important seismic sources in eastern/southeastern Turkey
2003, 2008). and that they need to be studied in detail.
Tectonic studies have mainly focused on the structures Southeastern Turkey presents several thrusts/blind
located in the north of the Bitlis–Zagros suture zone thrusts that can be determined by using asymmetrical fold
(Yiğitbaş and Yılmaz, 1996; Oberhanslı et al., 2010; Okay axes (Suppe, 1983; Mitra, 1990; Suppe and Medwedeff,
et al., 2010) but the structures of the Arabian foreland 1990). We interpret these structures, together with
were poorly studied (Lovelock, 1984; Biddle et al., 1987; their counterparts in northern Syria and Iraq, as having
* Correspondence: [email protected]
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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). about the internal structure of the SEAW that may
The cross-sectional geometry is very similar to that of a supply logical explanations for the thrust-related seismic
tectonic wedge occurring in accretionary prisms above activity recorded in the instrumental period, such as the
subduction zones (Figure 2). The tectonic wedges mimic 1975.09.06 (M:6.7) Lice and 2012.06.14 (M:5.5) Şırnak–
a wedge-shape pile of snow in front of a snowplow. The Silopi earthquakes.
shape of the wedge is related to (1) the applied force, (2)
the friction on the basal thrust, (3) the internal strength 2. The structure of the SEAW in the Arabian foreland
of the material in the wedge, and (4) the erosion of the The SEAW is located between the Bitlis–Zagros Suture
surface of the wedge (see Dahlen, 1990 for a review). Zone (BZSZ) and Sincar Mountain in Iraq (Figure 1). Its
In this paper, we aim to contribute to the understanding southern tip is represented by the Sincar–Kerkük Blind
of the SEAW. We particularly examine major asymmetrical Thrust Zone (SBTZ). The SEAW is mainly composed of
folds in the region using Google Earth images, because several thrust/blind thrust faults and related folds with
they would indicate the location of thrust/blind thrust some strike–slip faulting. The reverse and/or thrust faults
faulting. All these structures will provide information that reach the surface are marked by continuous red lines
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Figure 2. Tectonic wedge geometry (after Dahlen, 1990).
with triangles on the upthrust (hanging wall) side in the expected on the north of the Araban and Çakırhüyük
maps presented in this paper. The red broken dotted lines plains (Figure 4a–4e). They are bounded from the west
represent the approximate surface trace of blind thrusts by the NE–SW trending left lateral East Anatolian Fault
that is located in front of the forelimb. An asymmetrical Zone and in the east the left lateral Halfeti Fault cuts
fold is determined by the short or long drainage system asymmetrical anticlines (Figure 4a).
together with the blunt or sharp “v” of bedding traces in The Adıyaman Thrust Zone (ATZ) is located to the
the Google Images (Figure 3). north of the Halfeti Fault (Figures 5a and 5b). The Eocene
Quaternary deposits unconformably cover various units on the north thrust over Plio-Quaternary deposits
earlier lithostratigraphical units including an Upper (Ulu, 2002) on the south along with ATZ via Narince. The
Miocene unit containing mammalian fossils (Kaya et al., Halof dağı asymmetric anticline is located on the hanging
2012) in SE Turkey. wall of the ATZ, as shown on the geological cross section
The internal structure of the SEAW is explained below, of Sungurlu (1974) (Figure 5c). The limbs of the Halof
from west to east. dağı asymmetric anticline are clearly seen in Google Earth
Gaziantep area: to the NNW of the city of Gaziantep, images, where the anticline is seen to be partly eroded in
three prominent E–W trending plains are distinguished, Pınaryayla (Figure 5d). Their control of the topography
namely the Yavuzeli, Araban, and Çakırhüyük plains of the region indicates that the ATZ and north dipping
(Figure 4a). The linear E–W trending northern border of normal faults must be young structures (Figure 5e).
the Yavuzeli plain separates Quaternary deposits in the West of Diyarbakır: to the east of Narince, between the
south and Miocene limestones in the north (Ulu, 2002). villages of Ceylan and Yayıklı, a branch of active faulting
Two different drainage systems are recognized on the is separated from the ATZ. This NW–SE trending right
limestones: south flowing drainages are shorter than the lateral North Karacadağ Fault (NKF) (Emre et al., 2012)
north flowing one (Figures 4a–4c). This feature indicates is connected to the N–S trending Karacadağ Extensional
an asymmetrical anticline that may be related to a blind Fissure (KEF) (Şengör et al., 1985; Şaroğlu and Emre,
thrust (Figure 4d). A similar blind thrust is reported 1987). We suggest that the KEF might be connected to the
further to the south, just north of Kilis (Coşkun and Mardin Blind Thrust Zone (see next section) by a NW–SE
Coşkun, 2000). For this reason, identical structures are 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 arc-
second 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 in the region. The high angle southern limbs of the anticline
releasing bend between the NW–SE trending right lateral are limited by Quaternary and/or Plio-Quaternary deposits
strike–slip North and South Karacadağ faults that play the (Turhan et al., 2002) (Figures 7a and 7b). A close-up view
role of a tear fault between the ATZ and the Mardin Blind around the city of Mardin indicates that the city is located
Thrust Zone (Figure 6). While the NKF and KEF may be on the axis of a south verging asymmetrical anticline.
clearly followed on the topography and are mapped as Cretaceous neritic limestone is exposed in the core of this
Quaternary faults (Emre et al., 2012), the trace of the SKF anticline. The Eocene limestones have steep dipping beds
corresponds to the locations of the parasitic cones of the towards the south and are limited by the Quaternary fill of
Karacadağ volcano (Figure 6) that is drawn as a continuous the Mesopotamian plain (Turhan et al., 2002) (Figure 7c).
right lateral fault by using information from the shorter The axes of these asymmetrical anticlines are en echelon in
strike–slip segment on the geological map given by Turhan nature that might be the reflection of several splays of the
et al. (2002). MBTZ (Figures 7a and 8a). The MBTZ was shown on the
Mardin area: the Mardin Blind Thrust Zone (MBTZ) maps given by Lovelock (1984) and Perinçek et al. (1987)
can be drawn by following the asymmetrical anticline axes and in the cross section reported by Krasheninnikov
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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 Google Earth images (Figures 8b and 8c). The Pleistocene
between Nusaybin and İdil (Figure 8a) and continues uplift of the structure, due to the RTF, is represented by
to the west of Cizre. This zone can be traced along the three different alluvial terraces seen only on the northern
border of the S and SE dipping Eocene limestone unit and slopes of the Dicle river north of Hasankeyf (Yıldırım and
the Quaternary deposits of the Mesopotamian plain but Karadoğan, 2005) (Figure 8b).
it cannot be followed further NE due to the Quaternary Further to the north, the NW–SE trending Garzan
basalt lava flow around İdil (Turhan et al., 2002) (Figure Thrust Fault (GTF) is responsible for the formation of
8a). the Garzan asymmetric anticline (Figures 8d and 8e). The
North of MBTZ: to the north of Mardin, the Raman anticline axis and thrust fault are nearly parallel to each
Thrust Fault (RTF) is shown on geological maps (Turhan other, lying N 65 W. The northern limb of the anticline
et al., 2002; Yıldırım and Karadoğan 2011) and on the dips 15° while the southern limb has a steeper dipping,
cross section reported by Lovelock (1984). There is a slanting up to 75°, and is locally overturned (Sanlav et al.,
major asymmetrical fold axis on its hanging wall at Raman 1963; Ketin, 1983). The thrust fault dips 55° towards the
Dağı (Figures 8a–8c). The steeply dipping southern limb NE and has a 600 m vertical throw (based on correlation
and shallow dipping northern limb are clearly seen on the 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 Eocene units (Figure 10b). To the NE of Silopi, the tilted
of its steeply dipping limbs, well developed Quaternary Miocene beddings are in contact with Quaternary alluvial
deposits (Turhan et al., 2002) demonstrate that this is a fan deposits (Günay and Şenel, 2002) that indicate the
neotectonic structure. Silopi Blind Thrust Fault (SBT) and this structure continues
Another prominent structure is the Ergani–Silvan to the east towards Derker Ajam (northern Iraq) (Figure
Blind Trust Fault (EBT) determined by the south dipping 10a). Further south, the anticline at the Bikhayr mountains
beds that can be seen on Google Earth images. The axis (Ameen, 1991) in the south of Zaho (Iraq) and south of
of the asymmetric anticline is parallel to the thrust zone, Al-Malikiyah (Syria) indicates another blind thrust zone
which limits the Quaternary deposits particularly to the named the Bikhayr Blind Thrust Zone (BBTZ). This can be
south of Ergani (Tarhan, 2002) (Figure 9a). This thrust traced from Tepke (Syria) (Kent, 2010) to Dohuk (Iraq) via
zone is also the best source candidate for the 1975.09.06 Dayrabun (Iraq). No certain relationship between these
(Ms: 6.7) Lice earthquake (see below). structures has been established by using Google Earth
The EBT was recognized by Gilmour and Makel (1996) images but the BBTZ, the MBTZ, and the CTF overlap
in whose study the EBT and related fault-propagation each other around Al-Malikiyah and İdil (Figure 10a). All
folds were clearly seen in seismic reflection sections. The the structures in the Cizre–Silopi area are assumed to be
Hazro asymmetric anticline is located on the hanging wall connected by a basal thrust and their relationships with
of the EBT (Figures 9a–9c). The axis of the Hazro anticline each other and with the topography are shown in Figure
is eroded and the Silurian beds are exposed (Ketin, 1983) 10c.
(Figure 9b). The Sincar and Abdülaziz Mountains: Sincar Mountain
The Cizre–Silopi area: the WNW–ESE trending Cizre in Iraq is located 92 km south of the Mardin Blind Thrust
Thrust Fault (CTF) is shown on the MTA’s active fault map Zone (Figures 1 and 11a). The overall structure of Sincar
(Duman et al., 2012) and continues toward northern Iraq Mountain is a closed anticline, but a more detailed look
(Figure 10a). The CTF separates into a middle Triassic– reveals that it has a small syncline on the axis of a huge
Upper Cretaceous Cudi Group and lower–middle Eocene anticline (Figure 11b). The drainage pattern and shape of
units (Schmidt, 1964). In the hanging wall of the thrust, V’s of the bedding in both limbs of the anticline indicate
the Cudi group creates an asymmetric anticline and the that the northern limb has a higher dip value than the
footwall is composed of nearly vertical or overturned southern limb (see also the subsurface data reported by
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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 The western edge of Abdülaziz Mountain is probably
of the anticlines in southeast Turkey; this is probably connected to the Akçakale–Harran graben, with strike–
due to back thrusting under the northern limb of the slip faulting (the Abba fault of Lovelock, 1984) that is
Sincar anticline (Figure 11c). We evaluate that the Sincar subparallel to the Bozova Fault (BOF). In this case, it is
anticline was created by the Sincar–Kerkük Blind Thrust interesting to see that a more evolved and similar structure
Zone (SBTZ), representing the southernmost tip of the developed with the NKF, the KEF, and the SKF (Figure 1).
SEAW. This is followed towards the south of Musul via All the observations explained above demonstrate that
Tel Afer to the east (Kent, 2010) and towards Abdülaziz there is the SEAW in front of the BZSZ and its southern tip
Mountain to the west (Figure 1). Abdülaziz Mountain has is located in the Sincar–Kerkük Blind Thrust Zone.
a similar, but less prominent, structure (Sawaf et al., 1993;
Kent and Hickman, 1997; Rukieh et al., 2005) to Sincar 3. Morphometric analysis (mountain front sinuosity)
Mountain (Brew et al., 1999; 2001). The northern margin In order to evaluate the tectonic activity along thrust/blind
of Abdülaziz Mountain is limited by a south dipping thrust thrust faults, mountain front sinuosity (S ) values were
mf
fault (Sawaf et al., 1993; Kent and Hickman, 1997; Kazmin, determined as morphometric analysis (Figure 12). S is
mf
2005) that can be interpreted as a back thrusting similar defined as
to that of Sincar Mountain. The geomorphological map S = L /L,
mf mf s
of Syria compiled by K Mirzayev (Krasheninnikov, 2005) where L is the length of the mountain front along the mountain
mf
indicates that Abdülaziz Mountain is surrounded by upper range–basin boundary and L is the straight-line length of the
s
Quaternary and recent alluvial fans. 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 4. Seismotectonics of southeastern Turkey, northern
processes and tectonic activity. Tectonically active fronts Syria, and Iraq
generally have straight mountain range–piedmont (basin) The epicenter distribution of the earthquakes from the
junctions. S values lower than 1.4 indicate high tectonic Boğaziçi University Kandilli Observatory and Earthquake
mf
activity (Rockwell et al., 1984; Keller, 1986). Research Institute (KOERI, 1900–2015) strongly
In the present study, we performed S analysis on the documents some clusters in the region (Figure 13). It can
mf
mountain fronts that are related to the thrust/blind thrust easily be recognized that the left-lateral strike–slip East
fault segments (Figures 12b–12m). The analysis shows Anatolian Fault Zone (EAFZ) and the right-lateral North
that the S values of most of the segments are lower than Anatolian Fault Zone (NAFZ) are the main sources of
mf
1.4 (Figure 12n). This result indicates that the faults are earthquake occurrences in the region.
tectonically active in the region supported by the thrust- The second important earthquake cluster in the area
related seismic activity (see next section and Table), where is related to the 2011.10.23 Van earthquake (Mw: 7.1),
the GPS results show 17.8 ± 1.1 mm/year contraction which was created by a blind thrust (see below). It is
(Reilinger et al., 2006). Only some parts of the MBTZ have important to note that until this recent Van earthquake,
values higher than 1.4 and these segments can accordingly only the 1975.09.06 Lice earthquake (Ms: 6.7) was known
be evaluated as tectonically less active (Figure 12k). 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 In the NE of Syria, the sixth seismic cluster of moderate
of a quiescent period during the 20th century. Before the earthquakes is located around Haseki. This cluster is
2011 Van earthquake, seismicity data give an impression probably related to a NW–SE trending right-lateral tear
that right- and left-lateral strike–slip faults produced most fault in the Sincar–Kerkük Blind Thrust Zone. It should
of the earthquakes in the south of the BZSZ (Figure 13). be noted that our evaluation contradicts the interpretation
The third earthquake cluster is related to the right lateral given by Abdul-Wahed and Al-Tahhan (2010), whose
Bozova Fault and the marginal faults of the Akçakale/ study suggested E–W trending left-lateral strike–slip
Harran Graben, the forth seismic intensity seems to be faulting in this region.
related to the dextral Yüksekova–Şemdinli Fault, and the The focal depths of all catalog events (from 1900 to
fifth seismic intensity can be recognized around Silopi. 2015) for this region indicate that generally most of the
The 2012.06.14 Şırnak–Silopi earthquake (Mw: 5.1) (see events occurred in the crust (upper 30 km). However, we
below) indicates that the E–W thrusting (Bikhayr Blind observe that there are several deep earthquakes located as
Thrust Zone) is also a major neotectonic structure capable far down as 170 km. Their quantity is very low relative to
of producing major seismic events (Figure 13). the crustal events. Especially after the year 2000, which saw
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