Earthquake Report: Turkey!

I awakened to be late to attending the GSA meeting today. I had not checked the time. 7am is too early, but i understand the time differences…

As i was logging into Zoom, my coworker emailed our Tsunami Unit group about a M7 in the eastern Mediterranean. So, I shifted gears a bit. But i had my poster to present, so i had to stay somewhat focused on that.

Today, in the wee hours (my time in California), there was a M 7.0 earthquake offshore of western Turkey in the Icarian Sea. The earthquake mechanism (i.e. focal mechanism or moment tensor) was for an extensional type of an earthquake, slip along a normal fault.

I immediately thought about some quakes/deprems that happened there several years ago. This area is an interesting and complicated part of the world, tectonically.

  • 2017.07.20 M 6.7 Turkey
  • 2017.06.12 M 6.3 Turkey/Greece
  • To the north is a strike-slip plate boundary localized along the North Anatolia fault system. This is a right lateral fault system, where the plates move side by side, relative to each other. See the introductory information links below to learn more about different types of faults.

    To the south is a convergent plate boundary (plates are moving towards each other) related to (1) the Alpide Belt, a convergent plate boundary formed in the Cenozoic that extends from Australia to Morocco. On the southern side of Greece and western Turkey, there are subduction zones where the Africa plate dives northward beneath the Eurasia and Anatolia plates.

    The region of today’s earthquake is in a zone of north-south oriented extension. This extension appears to be in part due to gravitational collapse of uplifted metamorphic core complexes.

    There are several “massifs” that were emplaced in the past, lifted up, creating gravitational potential. The normal faults may have formed as the upper crust extended. It is complicated here, so i am probably missing some details. But, with the references i provide below, y’all can read more on your own. Feel free to contact me if i wrote something incorrect. I love my peer reviewers (you).

    So, this N-S extension creates east-west oriented valleys/basins with E-W striking (trending) faults. There are south dipping faults on the north sides and north dipping faults on the south side of these valleys.

    These structures are called rifts. A famous rift is the East Africa Rift.

    There are two main rifts in western Turkey, the Büyük Menderes Graben and the Küçük Menderes Graben Systems. If we project these rifts westward, we can see another rift, the rift that forms the Gulf of Corinth in Greece, the Gulf of Corinth Rift. This is one of the most actively spreading rifts in the world.

    In addition to the large earthquake, which caused lots of building damage and also caused over a dozen deaths so far (sadly), there was recorded a tsunami on the tide gages in the region. I use the IOC website to obtain tide gage data. This is an excellent service. There are only a few national tide gage online websites that rival this one.

    It is also highly likely that there were landslides or that there was liquefaction somewhere in the region. The USGS models i present below show a high likelihood for these earthquake triggered processes.

    Below is my interpretive poster for this earthquake

    • I plot the seismicity from the past month, with diameter representing magnitude (see legend). I include earthquake epicenters from 1920-2020 with magnitudes M ≥ 7.0 in one version.
    • I plot the USGS fault plane solutions (moment tensors in blue and focal mechanisms in orange), possibly in addition to some relevant historic earthquakes.
    • A review of the basic base map variations and data that I use for the interpretive posters can be found on the Earthquake Reports page. I have improved these posters over time and some of this background information applies to the older posters.
    • Some basic fundamentals of earthquake geology and plate tectonics can be found on the Earthquake Plate Tectonic Fundamentals page.

      I include some inset figures. Some of the same figures are located in different places on the larger scale map below.

    • On the left is a map from Armijo et al. (1999) that shows the plate boundary faults and tectonic plates in the region. This M 7.0 earthquake, denoted by the blue circle.
    • In the upper left corner is a map that shows the tectonic strain in the region. Areas of red are deforming more from tectonic motion than are areas that are blue. Learn more about the Global Strain Rate Map project here.
    • To the right of the strain map is a comparison of the shaking intensity modeled by the USGS and the shaking intensity based on peoples’ “boots on the ground” observations. A modeled estimate of intensity is shown by the color overlay and labels MMI 4, 5, 6, 7. The USGS Did You Feel It observations are the colored circles (color = intensity) and labeled dyfi 6.2 for example.
    • On the upper right and right center are two maps that show (bottom) liquefaction susceptibility and (top) landslide probability. These are based on empirical models from the USGS that show the chance an area may have experienced these processes that may have happened as a result of the ground shaking from the earthquake. I spend more time explaining these types of models and what they represent in this Earthquake Report for the recent event in Albania.
    • Faults shown on these maps come from the DISS fault database from INGV and their collaborators. These data have been incorporated into the Global Earthquake Model. The red lines represent the top of the fault plane and the green shapes represent the fault planes as they dip into the Earth. Note how the North Anatolia fault, which is a vertically dipping strike-slip fault, appears to not have fault planes. Why do you think that is?
    • In the lower right corner is a map showing epicenters for earthquakes since 30 July 2020 (from EMSC).
    • Along the bottom of the poster are several tsunami plots from the region. The Bodrum tide gage is on a south facing shoreline, so the waves are not directed directly at this gage. The Kos Marina and Hrakleio gages are more directly facing the earthquake. Note which gages have larger waves. Why do you think this is so?
    • Here are the main tide gages that have decent tsunami records in the Aegean region. I offset these records vertically a modest amount for the plot, so disregard the absolute elevation values.
    • I made a crude measurements for the wave height of these tsunami records (neglecting to take into account changes in tide). The locations are shown in the map.

    Other Report Pages

    Some Relevant Discussion and Figures

    • Here is a lovely plate tectonic overview map, highlighting the plate boundary faults, as well as the crustal faults (Taymaz et a., 2007).

    • Seismicity of the Eastern Mediterranean region and surroundings reported by USGS–NEIC during 1973–2007 with magnitudes for M . 3 superimposed on a shaded relief map derived from the GTOPO-30 Global Topography Data taken after USGS. Bathymetry data are derived from GEBCO/97–BODC, provided by GEBCO (1997) and Smith & Sandwell (1997a, b).

    • Here is the tectonic map from Dilek and Sandvol (2009).

    • Tectonic map of the Aegean and eastern Mediterranean region showing the main plate boundaries, major suture zones, fault systems and tectonic units. Thick, white arrows depict the direction and magnitude (mm a21) of plate convergence; grey arrows mark the direction of extension (Miocene–Recent). Orange and purple delineate Eurasian and African plate affinities, respectively. Key to lettering: BF, Burdur fault; CACC, Central Anatolian Crystalline Complex; DKF, Datc¸a–Kale fault (part of the SW Anatolian Shear Zone); EAFZ, East Anatolian fault zone; EF, Ecemis fault; EKP, Erzurum–Kars Plateau; IASZ, Izmir–Ankara suture zone; IPS, Intra–Pontide suture zone; ITS, Inner–Tauride suture; KF, Kefalonia fault; KOTJ, Karliova triple junction; MM, Menderes massif; MS, Marmara Sea; MTR, Maras triple junction; NAFZ, North Anatolian fault zone; OF, Ovacik fault; PSF, Pampak–Sevan fault; TF, Tutak fault; TGF, Tuzgo¨lu¨ fault; TIP, Turkish–Iranian plateau (modified from Dilek 2006).

    • This is a fantastic figure, yet quite complicated. This map shows teh plate boundaries, the GPS motions, and the tectonic strain for the region (Perouse et al., 2012).
    • We use GPS sites at specific locations to measure how fast the Earth’s crust moves due to plate tectonics and other reasons. These GPS sites are almost constantly recording their geographic position. If a GPS site is moving, we can take two observations (lets say a year apart), measure their relative distance, and divide the time between the measurements to get the velocity (the speed) that this GPS site is moving. The white vectors (the arrows) show the direction those GPS sites are moving and the length of the vector represents its velocity. The black arrows show what the plate motion rates are at the plate boundaries and these are modeled using lots of different data sources (not just GPS).
    • Tectonic strain is a measure of how much the Earth’s crust is deforming over time. The higher the tectonic strain rate (i.e. red), the more tectonic stress is being accumulated in the crust and along faults. Areas of higher strain are places where there are more likely to be larger or more (or both) earthquakes.

    • Present-day kinematic and tectonic map encompassing the Central and Eastern Mediterranean, summarizing our main results and interpretations. Our kinematic model includes rigid-block motions as well as localized and distributed strain. Central-SW Aegean block (CSW AEG block) and East Anatolian block (East Anat. block) are purely kinematic and directly results from strain modeling (Figure 5). AP-IO Block is our Apulian-Ionian block with tentative tectonic boundaries. Rotation pole of this Apulian-Ionian block relative to Nubia (Nu WAp-Io) and to Eurasia (Eu WAp-Io) are shown with their 95% confidence ellipse.

    • This is the Ersoy et al. (2014) map showing their interpretation of the modern deformation in the northern Aegean Sea and western Turkey.

    • Geological map showing the distribution of the Menderes Extensional Metamorphic Complex (MEMC), Oligocene–Miocene volcanic and sedimentary units and volcanic centers in the Aegean Extensional Province (compiled from geological maps of Greece (IGME) and Turkey (MTA), and adapted from Ersoy and Palmer, 2013). Extensional deformation field with rotation (rotational extension) is shown with gray field, and simplified from Brun and Sokoutis (2012), Kissel et al. (2003) and van Hinsbergen and Schmid (2012). İzmir–Balıkesir Transfer zone (İBTZ) give the outer limit for the rotational extension, and also limit of ellipsoidal structure of the MEMC. MEMC developed in two stages: the first one was accommodated during early Miocene by the Simav Detachment Fault (SDF) in the north; and the second one developed during Middle Miocene along the Gediz (Alaşehir) Detachment Fault (GDF) and Küçük Menderes Detachment Fault (KMDF). Extensional detachments were also accommodated by strike-slip movement along the İBTZ (Ersoy et al., 2011) and Uşak–Muğla Transfer Zone (Çemen et al., 2006; Karaoğlu and Helvacı, 2012). Other main core complexes in the Aegean, the Central Rhodope (CRCC), Southern Rhodope (SRCC), Kesebir–Kardamos Dome (KKD) and Cycladic (CCC) Core Complexes are also shown. The area bordered with dashed green line represents the surface trace of the asthenospheric window between the Aegean and Cyprean subducted slabs (Biryol et al., 2011; de Boorder et al., 1998). See text for detail.

    • This is a great figure showing another interpretation to explain the extension in this region (slab rollback and mantle flow) from Brun and Sokoutis (2012).

    • Mantle flow pattern at Aegean scale powered by slab rollback in rotation around vertical axis located at Scutary-Pec (Albania). A: Map view of fl ow lines above (red) and below (blue) slab. B: Three-dimensional sketch showing how slab tear may accommodate slab rotation. Mantle fl ow above and below slab in red and blue, respectively. Yellow arrows show crustal stretching.

  • Below is a series of figures from Jolivet et al. (2013). These show various data sets and analyses for Greece and Turkey.
  • Upper Panel (A): This is a tectonic map showing the major faults and geologic terranes in the region. The fault possibly associated with today’s earthquake is labeled OU on the map, for the Ula-Oren fault.
  • Lower Panel (B): This shows historic seismicity for the region. Note the general correlation with the faults in the upper panel.

  • A: Tectonic map of the Aegean and Anatolian region showing the main active structures
    (black lines), the main sutures zones (thick violet or blue lines), the main thrusts in the Hellenides where they have not been reworked by later extension (thin blue lines), the North Cycladic Detachment (NCDS, in red) and its extension in the Simav Detachment (SD), the main metamorphic units and their contacts; AlW: Almyropotamos window; BD: Bey Daglari; CB: Cycladic Basement; CBBT: Cycladic Basement basal thrust; CBS: Cycladic Blueschists; CHSZ: Central Hellenic Shear Zone; CR: Corinth Rift; CRMC: Central Rhodope Metamorphic Complex; GT: Gavrovo–Tripolitza Nappe; KD: Kazdag dome; KeD: Kerdylion Detachment; KKD: Kesebir–Kardamos dome; KT: Kephalonia Transform Fault; LN: Lycian Nappes; LNBT: Lycian Nappes Basal Thrust; MCC: Metamorphic Core Complex; MG: Menderes Grabens; NAT: North Aegean Trough; NCDS: North Cycladic Detachment System; NSZ: Nestos Shear Zone; OlW: Olympos Window; OsW: Ossa Window; OSZ: Ören Shear Zone; Pel.: Peloponnese; ÖU: Ören Unit; PQN: Phyllite–Quartzite Nappe; SiD: Simav Detachment; SRCC: South Rhodope Core Complex; StD: Strymon Detachment; WCDS: West Cycladic Detachment System; ZD: Zaroukla Detachment. B: Seismicity. Earthquakes are taken from the USGS-NEIC database. Colour of symbols gives the depth (blue for shallow depths) and size gives the magnitude (from 4.5 to 7.6).

  • Upper Panel (C): These red arrows are Global Positioning System (GPS) velocity vectors. The velocity scale vector is in the lower left corner. The main geodetic (study of plate motions and deformation of the earth) signal here is the westward motion of the North Anatolian fault system as it rotates southward as it traverses Greece. The motion trends almost south near the island of Crete, which is perpendicular to the subduction zone.
  • Lower Panel (D): This map shows the region of mid-Cenozoic (Oligo-Miocene) extension (shaded orange). It just happens that there is still extension going on in parts of this prehistoric extension.

  • C: GPS velocity field with a fixed Eurasia after Reilinger et al. (2010) D: the domain affected by distributed post-orogenic extension in the Oligocene and the Miocene and the stretching lineations in the exhumed metamorphic complexes.

  • Upper Panel (E): This map shows where the downgoing slab may be located (in blue), along with the volcanic centers associated with the subduction zone in the past.
  • Lower Panel (F): This map shows the orientation of how seismic waves orient themselves differently in different places (anisotropy). We think seismic waves travel in ways that reflects how tectonic strain is stored in the earth. The blue lines show the direction of extension in the asthenosphere, green lines in the lithospheric mantle, and red lines for the crust.

  • E: The thick blue lines illustrate the schematized position of the slab at ~150 km according to the tomographic model of Piromallo and Morelli (2003), and show the disruption of the slab at three positions and possible ages of these tears discussed in the text. Velocity anomalies are displayed in percentages with respect to the reference model sp6 (Morelli and Dziewonski, 1993). Coloured symbols represent the volcanic centres between 0 and 3 Ma after Pe-Piper and Piper (2006). F: Seismic anisotropy obtained from SKS waves (blue bars, Paul et al., 2010) and Rayleigh waves (green and orange bars, Endrun et al., 2011). See also Sandvol et al. (2003). Blue lines show the direction of stretching in the asthenosphere, green bars represent the stretching in the lithospheric mantle and orange bars in the lower crust.

  • Upper Panel (G): This is the map showing focal mechanisms in the poster above. Note the strike slip earthquakes associated with the North Anatolian fault and the thrust/reverse mechanisms associated with the thrust faults.

  • G: Focal mechanisms of earthquakes over the Aegean Anatolian region.

    • Here is another map showing the GPS plate motion rates from Perouse et al. (2012). Note the scale on the two map panels are different. The rates on the map on the right are much faster than the rates in Africa.

    • Input GPS velocities of the model. Velocities are in Eurasia fixed reference frame with their respective 95% confidence ellipse. Velocity vectors are color coded relative to the study they have been taken from (see paper for more details). (a) GPS velocities of the entire Nubian plate used to constrain the Nubia–Eurasia relative motion. Nubia–Eurasia rotation pole defined in this and previous studies are shown with their 1s confidence ellipse: circle, Calais et al. [2003]; diamond, Le Pichon and Kreemer [2010]; open square, D’Agostino et al. [2008]; triangle, Argus et al. [2010]; filled square, Reilinger et al. [2006]; red star, present study. Parameters of these rotation poles are summarized in Table 2. (b) Focus on the GPS velocities in the Central and Eastern Mediterranean region.

    • Here is a map that shows historic earthquake mechanisms (Perouse et al., 2012).

    • Input seismic moment tensors of the model. Fault plane solutions are from the Harvard CMT catalog (from 1976 to 2007) and the Regional Centroid Moment Tensor (RCMT) catalog (from 1995 to 2007). Location and hypocenter depth of the events are relocalized according to the Engdahl et al. [1998] catalog.

    Those Rifts

    • First we can see this map that highlights all the grabens mapped in the region. A graben is basically a block of Earth that has moved relatively down, forming a valley.
    • These grabens are bound on at least one side by a normal fault (shown here with stippled lines pointing in the direction that the faults dip into the Earth.

    • Outline geological map of western Anatolia showing Neogene and Quaternary basins [simplified from Bingo1 (1989).

    • Here is a map of the western part of the Buyuk Menderes Graben valley (Bozcurt 2000). The main reason to show this is because it shows the location of the cross-section shown next (in the box labeled “Figure 6b”).
    • The island labeled Chios here is also called Samos on other maps.

    • Simplified geological map of the northern margin of the Btiytik Menderes Graben in the area between Germencik and Umurlu.

    • Here is the cross section that shows their interpretation of the tectonic faults in the subsurface.

    • Geological cross-section of the northern margin of the Bt~yt~k Menderes Graben (see Fig. 6b for location) based on fig. llb of Cohen et al. (1995). This cross-section indicates a total of c. 5 km of extension. Assuming a uniform extension rate, the age of the fault zone is (c. 5 km/1 mm a -1) 5 Ma. More details in the paper.

    • Here is a low-angle oblique illustrative view of the Graben forming basin common in the region (Emre and Sozbilir, 2007..

    • Let’s now venture offshore into the ocean. This map shows some geologic units, some mapped crustal faults, and some seismic lines (Ocakoglu et al., 2005). These seismic lines are shown as rows of dots.
    • Each straight dotted line represents a path that a research vessel took to make observations about the subsurface using seismic waves. The 30 Oct 2020 M 7.0 earthquake was to the north of Samos.
    • None of the seismic lines are optimally located to look for the fault that ruptured earlier today, but they may help us learn about what might be possible here.

    • Geology map of the study area (simplified from MTA 1: 500,000 scale geology map) and location of the seismic lines. Active faults are marked onland with bold lines.

    • Here are some seismic lines (seismic reflection profiles), whose locations are shown on the above map. The upper two panels are relevant (see line 10 on the map). These are consistent with normal faults on the north side of the basin.

    • Time migrated seismic sections, offshore Teke and Karaburun, showing active normal faults marked with white lines and strike-slip faults with black lines (see Fig. 3A for locations). Vertical exaggeration is ~2. Observed vertical displacement on the seafloor and basement surface by normal fault (marked with bold circle on Line-10) looks the same, thus this normal fault is Quaternary age. On line-18, vertical displacement seen on basement units are greater than displacement on Pliocene–Quaternary deposits due to fault marked with a bold circle thus this normal fault can be interpreted as Later Miocene–Pliocene age.

    • I include this map to show that there are lots of faults in this area. This is their final fault map based on the interpretations of many seismic lines.

    • (A) The correlations between offshore and onshore active fault systems in the study region. N–S, NE–SW and NW–SE oriented lines and dashed-lines show interpreted active strike-slip faults and their possible extensions. These faults are annotated with dNT for those at north and dST for those at south. E–W oriented lines and dashed lines show interpreted active normal faults and their possible continuations, with footwalls indicated by the plus symbol. (B) Simplified active fault map of the study area. The bold lines show the master active faults. (C) Pureshear model can explain the development of active structures in the study area.

    • Below are a map and a cross section further to the east, in the eastern part of the Büyük Menderes Graben (Kaya, 2015). They were studying geotherm water in the region as it relates to the fault geometry and other factors. and, well, who doesn’t like a little pre-planning at a hot spring?

    • Geological map of western Turkey showing the Menderes massif and its subdivision into the AG Alasehir graben, the BMG Büyük Menderes graben, the CMM Central Menderes massif, the KMG Küçük Menderes graben, the NMM Northern Menderes massif and the SMM Southern Menderes massif, modified from Sengör and Bozkurt (2013).

    • Here is the cross-section, showing normal faults bounding the graben.

    • (a) A conceptual model of geothermal circulation in the study area, (b) a deep seismic profile with the N–S direction taken from a 30 km west of study area (Nazilli region) (Çifçi et al., 2011). Roman numerals indicate the different sedimentary sequences.

    • Let’s look at this yet another way. Below is a map and series of cross sections along the Küçük Menderes Graben (KMG). Rojay et al. (2005) take a look at the Plio-Quaternary history of the KMG. The KMG is the rift to the north of the Buyuk Menderes Graben.

    • Simplified geological map of the KMG showing the positions of geological cross-sections.

    • Here is a series of cross sections along this basin, locaions are shown on the previous map.

    • Series of geological cross-sections showing various sectors of the KMG depicting horst and graben structures overprinted onto the huge synclinal structure (see Fig. 3 for positions of geological cross-sections).

    • Here is their model of how the regional deformation is driven by the metamorphic core complex process.

    • Schematic tentative cross-sections showing the Miocene to Quaternary evolution of the KMG (modified from Erinç [66]). Note the continuing extension since Miocene.

    Regional Cross Sections

    • The following three figures are from Dilek and Sandvol, 2006. The locations of the cross sections are shown on the map as orange lines. Cross section G-G’ is located in the region of today’s earthquake.
    • Here is the map (Dilek and Sandvol, 2006). I include the figure caption below in blockquote.

    • Simplified tectonic map of the Mediterranean region showing the plate boundaries, collisional zones, and directions of extension and tectonic transport. Red lines A through G show the approximate profile lines for the geological traverses depicted in Figure 2. MHSZ—mid-Hungarian shear zone; MP—Moesian platform; RM—Rhodope massif; IAESZ— Izmir-Ankara-Erzincan suture zone; IPS—Intra-Pontide suture zone; ITS—inner Tauride suture zone; NAFZ—north Anatolian fault zone; KB—Kirsehir block; EKP—Erzurum-Kars plateau; TIP—Turkish-Iranian plateau.

    • Here are cross sections A-D (Dilek and Sandvol, 2006). I include the figure caption below in blockquote.

    • Simplified tectonic cross-sections across various segments of the broader Alpine orogenic belt.

    • (A) Eastern Alps. The collision of Adria with Europe produced a bidivergent crustal architecture with both NNW- and SSE-directed nappe structures that involved Tertiary molasse deposits, with deep-seated thrust faults that exhumed lower crustal rocks. The Austro-Alpine units north of the Peri-Adriatic lineament represent the allochthonous outliers of the Adriatic upper crust tectonically resting on the underplating European crust. The Penninic ophiolites mark the remnants of the Mesozoic ocean basin (Meliata). The Oligocene granitoids between the Tauern window and the Peri-Adriatic lineament represent the postcollisional intrusions in the eastern Alps. Modified from Castellarin et al. (2006), with additional data from Coward and Dietrich (1989); Lüschen et al. (2006); Ortner et al. (2006).
    • (B) Northern Apennines. Following the collision of Adria with the Apenninic platform and Europe in the late Miocene, the westward subduction of the Adriatic lithosphere and the slab roll-back (eastward) produced a broad extensional regime in the west (Apenninic back-arc extension) affecting the Alpine orogenic crust, and also a frontal thrust belt to the east. Lithospheric-scale extension in this broad back-arc environment above the west-dipping Adria lithosphere resulted in the development of a large boudinage structure in the European (Alpine) lithosphere. Modified from Doglioni et al. (1999), with data from Spakman and Wortel (2004); Zeck (1999).
    • (C) Western Mediterranean–Southern Apennines–Calabria. The westward subduction of the Ionian seafloor as part of Adria since ca. 23 Ma and the associated slab roll-back have induced eastward-progressing extension and lithospheric necking through time, producing a series of basins. Rifting of Sardinia from continental Europe developed the Gulf of Lion passive margin and the Algero-Provencal basin (ca. 15–10 Ma), then the Vavilov and Marsili sub-basins in the broader Tyrrhenian basin to the east (ca. 5 Ma to present). Eastward-migrating lithospheric-scale extension and
      necking and asthenospheric upwelling have produced locally well-developed alkaline volcanism (e.g., Sardinia). Slab tear or detachment in the Calabria segment of Adria, as imaged through seismic tomography (Spakman and Wortel, 2004), is probably responsible for asthenospheric upwelling and alkaline volcanism in southern Calabria and eastern Sicily (e.g., Mount Etna). Modified from Séranne (1999), with additional data from Spakman et al. (1993); Doglioni et al. (1999); Spakman and Wortel (2004); Lentini et al. (this volume).
    • (D) Southern Apennines–Albanides–Hellenides. Note the break where the Adriatic Sea is located between the western and eastern sections along this traverse. The Adria plate and the remnant Ionian oceanic lithosphere underlie the Apenninic-Maghrebian orogenic belt. The Alpine-Tethyan and Apulian platform units are telescoped along ENE-vergent thrust faults. The Tyrrhenian Sea opened up in the latest Miocene as a back-arc basin behind the Apenninic-Maghrebian mountain belt. The Aeolian volcanoes in the Tyrrhenian Sea represent the volcanic arc system in this subduction-collision zone environment. Modified from Lentini et al. (this volume). The eastern section of this traverse across the Albanides-Hellenides in the northern Balkan Peninsula shows a bidivergent crustal architecture, with the Jurassic Tethyan ophiolites (Mirdita ophiolites in Albania and Western Hellenic ophiolites in Greece) forming the highest tectonic nappe, resting on the Cretaceous and younger flysch deposits of the Adria affinity to the west and the Pelagonia affinity to the east. Following the emplacement of the Mirdita- Hellenic ophiolites onto the Pelagonian ribbon continent in the Early Cretaceous, the Adria plate collided with Pelagonia-Europe obliquely starting around ca. 55 Ma. WSW-directed thrusting, developed as a result of this oblique collision, has been migrating westward into the peri-Adriatic depression. Modified from Dilek et al. (2005).
    • (E) Dinarides–Pannonian basin–Carpathians. The Carpathians developed as a result of the diachronous collision of the Alcapa and Tsia lithospheric blocks, respectively, with the southern edge of the East European platform during the early to middle Miocene (Nemcok et al., 1998; Seghedi et al., 2004). The Pannonian basin evolved as a back-arc basin above the eastward retreating European platform slab (Royden, 1988). Lithospheric-scale necking and boudinage development occurred synchronously with this extension and resulted in the isolation of continental fragments (e.g., the Apuseni mountains) within a broadly extensional Pannonian basin separating the Great Hungarian Plain and the Transylvanian subbasin. Steepening and tearing of the west-dipping slab may have caused asthenospheric flow and upwelling, decompressional melting, and alkaline volcanism (with an ocean island basalt–like mantle source) in the Eastern Carpathians. Modified from Royden (1988), with additional data from Linzer (1996); Nemcok et al. (1998); Doglioni et al. (1999); Seghedi et al. (2004).
    • (F) Arabia-Eurasia collision zone and the Turkish-Iranian plateau. The collision of Arabia with Eurasia around 13 Ma resulted in (1) development of a thick orogenic crust via intracontinental convergence and shortening and a high plateau and (2) westward escape of a lithospheric block (the Anatolian microplate) away from the collision front. The Arabia plate and the Bitlis-Pütürge ribbon continent were probably amalgamated earlier (ca. the Eocene) via a separate collision event within the Neo-Tethyan realm. BSZ—Bitlis suture zone; EKP—Erzurum-Kars plateau. A slab break-off and the subsequent removal of the lithospheric mantle (lithospheric delamination) beneath the eastern Anatolian accretionary complex caused asthenospheric upwelling and extensive melting, leading to continental volcanism and regional uplift, which has contributed to the high mean elevation of the Turkish-Iranian plateau. The Eastern Turkey Seismic Experiment results have shown that the crustal thickness here is ~ 45–48 km and that the Turkish-Iranian plateau is devoid of mantle lithosphere. The collision-induced convergence has been accommodated by active diffuse north-south shortening and oblique-slip faults dispersing crustal blocks both to the west and the east. The late Miocene through Plio-Quaternary volcanism appears to have become more alkaline toward the south in time. The Pleistocene Karacadag shield volcano in the Arabian foreland represents a local fissure eruption associated with intraplate extension. Data from Pearce et al. (1990); Keskin (2003); Sandvol et al. (2003); S¸engör et al. (2003).
    • (G) Africa-Eurasia collision zone and the Aegean extensional province. The African lithosphere is subducting beneath Eurasia at the Hellenic trench. The Mediterranean Ridge represents a lithospheric block between the Africa and Eurasian plate (Hsü, 1995). The Aegean extensional province straddles the Anatolide-Tauride and Sakarya continental blocks, which collided in the Eocene. NAF—North Anatolian fault. South-transported Tethyan ophiolite nappes were derived from the suture zone between these two continental blocks. Postcollisional granitic intrusions (Eocone and Oligo-Miocene, shown in red) occur mainly north of the suture zone and at the southern edge of the Sakarya continent. Postcollisional volcanism during the Eocene–Quaternary appears to have migrated southward and to have changed from calc-alkaline to alkaline in composition through time. Lithospheric-scale necking, reminiscent of the Europe-Apennine-Adria collision system, and associated extension are also important processes beneath the Aegean and have resulted in the exhumation of core complexes, widespread upper crustal attenuation, and alkaline and mid-ocean ridge basalt volcanism. Slab steepening and slab roll-back appear to have been at work resulting in subduction zone magmatism along the Hellenic arc.
    • Here is another cross section that shows the temporal evolution of the tectonics of this region in the area of cross section G-G’ above (Dilek and Sandvol, 2009).

    • Late Mesozoic–Cenozoic geodynamic evolution of the western Anatolian orogenic belt as a result of collisional
      and extensional processes in the upper plate of north-dipping subduction zone(s) within the Tethyan realm. See text
      for discussion.


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