Fethiye Burdur Fault Zone Research Articles

Evaluation of soft sediment deformation structures along the Fethiye–Burdur Fault Zone, SW Turkey

Burdur city is located on lacustrine sedimentary deposits at the northeastern end of the Fethiye–Burdur Fault Zone (FBFZ) in SW Turkey. Fault steps were formed in response to vertical displacement along normal fault zones in these deposits. Soft sediment deformation structures were identified at five sites in lacustrine sediments located on both sides of the FBFZ. The deformed sediments are composed of unconsolidated alternations of sands, silts and clay layers and show different morphological types. The soft sediment deformation structures include load structures, flame structures, slumps, dykes, neptunian dykes, drops and pseudonodules, intercalated layers, ball and pillow structures, minor faults and water escape structures of varying geometry and dimension. These structures are a direct response to fluid escape during liquefaction and fluidization mechanism. The driving forces inferred include gravitational instabilities and hydraulic processes. Geological, tectonic, mineralogical investigations and age analysis were carried out to identify the cause for these soft sediment deformations. OSL dating indicated an age ranging from 15161±744 to 17434±896 years for the soft sediment deformation structures. Geological investigations of the soft sediment deformation structures and tectonic history of the basin indicate that the main factor for deformation is past seismic activity.

Optically stimulated luminescence (OSL) dating of quartz grains within the sand dykes cutting the lacustrine deposits in the Burdur area (SW Turkey) and its tectonic interpretation

Burdur city is located on a lacustrine sedimentary deposit at the northeastern end of the Fethiye–Burdur Fault Zone (FBFZ) in SW Turkey. Fault steps were formed in response to vertical displacement along normal fault zones in these deposits. Geological, tectonic, mineralogical investigations and age analysis were carried out to identify the liquefied material. Paleoliquefaction characterized by sand and mud dykes is observed in three different locations. For this study, in order to investigate the relationship of sand and mud dykes with liquefaction, the present geologic and hydrogeologic environment, evolution of the host sediments and the paleoenvironment corresponding to duration of liquefaction were investigated. Field work was carried out and laboratory experiments were performed on the samples taken from liquefied soils and clayey lacustrine sediments cut by sand and mud dykes. The mineralogical features of the clays and age analysis of the liquefied materials were examined in the experimental studies. As a result of the X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) micrographs, the liquefied clay mineral assemblage in the soil samples contains illite. Optically stimulated luminescence (OSL) dating analysis has indicated an age ranging from 15,161 ± 744 to 17,434 ± 896 years for the liquefaction features. Assuming the groundwater level to be at critical depth, it was concluded that there was no possibility of liquefaction in most parts of the settlement during an earthquake.

Comment on “The Fethiye–Burdur Fault Zone: A component of upper plate extension of the subduction transform edge propagator fault linking Hellenic and Cyprus Arcs, Eastern Mediterranean. Tectonophysics 635, 80–99” by J. Hall, A.E. Aksu, İ. Elitez, C. Yaltırak, G. Çiftçi

• NE-trending Pliny–Strabo trench has envisaged being continued into Anatolia as strike-slip fault.

Reply to the comment by M.C. Alçiçek on “The Fethiye–Burdur Fault Zone: A component of upper plate extension of the subduction transform edge propagator fault linking Hellenic and Cyprus Arcs, Eastern Mediterranean,” Tectonophysics, 635, 80–99, by J. Hall, A.E. Aksu, İ. Elitez, C. Yaltirak and G. Çifçi

• This confirms our previous suggestions that the Fethiye-Burdur Fault Zone is a 75-90 km-wide, left-lateral, fault zone. • This is based on GPS vectors, earthquake first motions, magnetotelluric data and detailed mapping including fault kinematics.

The Fethiye–Burdur Fault Zone: A component of upper plate extension of the subduction transform edge propagator fault linking Hellenic and Cyprus Arcs, Eastern Mediterranean

The Hellenic and Cyprus Arcs, that mark the convergent boundary of the African and Aegean–Anatolian plates, are offset along a subduction transform edge propagator (‘STEP’) fault running NE–SW along the Pliny and Strabo Trenches. The continuation of the fault to the northeast through the Rhodes Basin and into SW Anatolia is assessed. Seismic reflection profiles show that the structural architecture of the northern sector of the Rhodes Basin includes a large crustal-scale fold–thrust belt which is overprinted by numerous faults with small extensional stratigraphic separations. A protracted episode of convergence in the Miocene resulted in the development of a prominent NE–SW-striking and NW-verging fold–thrust belt in the Rhodes Basin. The absence of evaporites in the Rhodes Basin and several seaward prograded vertically stacked Quaternary delta successions resting at 2500–3500m water depth collectively suggest that the Rhodes Basin must have remained above the depositional base of marine evaporite environment during the Messinian and that the region must have subsided very rapidly during the Pliocene-Quaternary. During the Pliocene-Quaternary, a NE–SW-trending belt developed across the Rhodes Basin: while the structural framework of this belt was characterised by reactivated thrusts in the central portion of the basin, a prominent zone of NE–SW-striking and NW- and SE-dipping faults with extensional separations developed in the northern portion of the basin. Two seismic profiles running parallel to the present-day coastline provide the much needed linkage between the Fethiye–Burdur Fault Zone onland and the reactivated thrusts in central Rhodes Basin, and show that the Pliocene-Quaternary zone of high-angle faults with extensional separations clearly link with the similarly trending and dipping strike–slip faults onland in the Eşen Valley, thus providing the continuity between the Pliny–Strabo Trenches in the southwest and the Fethiye–Burdur Fault Zone in the northeast. Mapping of many faults in parts of the Fethiye–Burdur Fault Zone shows evidence for sinistral strike–slip but total displacement across the fault zone is at maximum a few tens of kilometres. The STEP fault thus appears to have diminishing displacement associated with it as it propagates upwards into the upper plate from its originating tear in the subducting plate.

Tectonic activity inferred from velocity field of GNSS measurements in Southwest of Turkey

Turkey occupies a critical segment in the Alpine-Himalayan orogenic belt that is characterized by many active fault lines. Numerous earthquakes of varying magnitudes have occurred on these fault lines over the years. A significant portion of these earthquakes have been recorded along the Fethiye Burdur Fault Zone (FBFZ). Unfortunately, the latest earthquakes that happened on the FBFZ led to a large loss of human life and extensive economic losses. Southwest Anatolia, including the FBFZ, is monitored by 44 Global Navigation Satellite System (GNSS) stations, comprised of 16 permanent and 28 campaign stations. Measurements have been conducted by combining observations from 2003 to 2006 (Erdogan et al. in J. Earthq. Eng. 12(2):109–118, 2008) with new observations from 2009 and 2010. The combined processes have yielded an updated velocity field of the region. In addition, the effects of the post 2007 earthquakes on the GNSS stations were also investigated. The strain analysis based on the observations made between 2003 and 2010 display high consistency with the earthquakes that occurred in the region. Also, it was observed that the strain analysis is in accordance with the North-South opening created as a result of the African plate being submerged under the Anatolian plate in the southern of the island of Crete.

Plio-Quaternary Stress State in the Burdur Basin, SW-Turkey

This study defines the Plio-Quaternary to present day stress regime in the Burdur Basin, located at the northeastern end of the Fethiye–Burdur Fault Zone in SW Turkey. This fault length, which is considered the landward continuation of the Pliny-Strabo trench, is an important feature in SW Turkey. The inversion slip vectors measured on fault planes indicate a consistent normal faulting stress regime during Plio-Quaternary time, continuing into recent times as indicated by earthquake focal mechanism inversions. Both states have consistent NW–SE trending horizontal minimum stress axes (σ3). The orientation of fault sets is predominantly around the NE–SW direction in the major Fethiye–Burdur Fault Zone, making the extension NW–SE. The mean stress ratio is 0.74 indicating a triaxial stress state, which is clearly different from radial extension. The NW–SE extension is probably responsible for the formation of the Burdur Basin during Plio-Quaternary time. This extension, which is probably caused by slab-pull force due to the subduction process along the Cyprus arc, produces a dominant normal motion along the FBFZ.

Investigation of Fethiye-Marmaris Bay (SW Anatolia): seismic and morphologic evidences from the missing link between the Pliny Trench and the Fethiye-Burdur Fault Zone

New (2009) multi-beam bathymetric and previously published seismic reflection data from the NE-SW-oriented Fethiye Bay and the neighboring N-S-oriented Marmaris Bay off SW Anatolia were evaluated in order to interpret the seafloor morphology in terms of the currently still active regional tectonic setting. This area lies between the Pliny Trench, which constitutes the eastern sector of the subduction zone between the African and Eurasian plates in the Eastern Mediterranean, and the Fethiye-Burdur Fault Zone of the Anatolian Plate. The bathymetric data document the very narrow shelf of the Anatolian coast, a submarine plain between the island of Rhodes and Marmaris Bay, and a large canyon connecting the abyssal floor of the Rhodes Basin with Fethiye Bay. The latter are here referred to as the Marmaris Plain and Fethiye Canyon, respectively. Several active and inactive faults have been identified. Inactive faults (faults f1) delineate a buried basin beneath the Marmaris Plain, here referred to as the Marmaris Basin. Other faults that affect all stratigraphic units are interpreted as being active. Of these, the NE-SW-oriented Marmaris Fault Zone located on the Marmaris Plain is interpreted as a transtensional fault zone in the seismic and bathymetric data. The transtensional character of this fault zone and associated normal faults (faults f3) on the Marmaris Plain correlates well with the Fethiye-Burdur Fault Zone on land. Another important fault zone (f4) occurs along the Fethiye Canyon, forming the northeastern extension of the Pliny Trench. The transpressional character of faults f4 inferred from the seismic data is well correlated with the compressional structures along the Pliny Trench in the Rhodes Basin and its vicinity. These observations suggest that the Marmaris Fault Zone and faults f3 have evolved independently of faults f4. The evidence for this missing link between the Pliny Trench and the Fethiye-Burdur Fault Zone implies possible kinematic problems in this tectonic zone that deserve further detailed studies. Notably, several active channels and submarine landslides interpreted as having been triggered by ongoing faulting attest to substantial present-day sediment transport from the coast into the Rhodes Basin.

Testing a logic tree approach for archaeoseismology to the ancient city of Pınara (SW Turkey)

Geologists, seismologists, as well as archaeologists increasingly apply archaeoseismological investigations to study possible natural causes of damage of a site and to assess the regional seismic hazard risks. Archaeoseismological investigations enable the obtaining of diverse data on past earthquakes and allow for an application of different methods. Furthermore, archaeoseismology provides the opportunity to study past earthquakes in regions where limited instrumental and historical data are available. Therefore, this approach contributes to a regional assessment of seismic hazard. The increasing application and importance of archaeoseismology requires a comprehensive and systematic approach. The logic tree methodology for archaeoseismology is an evaluation method which offers a standard procedure to identify and evaluate archaeoseismological information and to provide comparable values for seismic hazard assessment. This study tests the logic tree methodology for archaeoseismology to Pınara to assess the city’s potential to have recorded earthquakes, and the methodology’s value. The ancient city of Pınara (SW Turkey, 500 BC–900 AD) is situated in the Eşen basin in the southern extremity of the seismically active Fethiye-Burdur fault zone. The present seismic quiescence of the Eşen basin contradicts the geological and historical records which indicate that fault and earthquake activity must have been recurrent. With the application of the logic tree approach to Pınara, geological and archaeoseismological evidence of seismic activity is evaluated in six stages. The end solution of the logic tree provides a value between 0 and 1. This archaeological quality factor (AQF) reflects the reliability and relative significance of Pınara for archaeoseismological investigation and seismic hazard assessment respectively. Pınara’s preferred end solution (P es1) of 0.06 and the AQF of 0.12 are obtained by the logic tree method and reflect the high probability of recorded palaeoearthquakes in Pınara. In sum, the logic tree for archaeoseismology provides a concept with reliable criteria to assess the earthquake hypothesis in general, and the findings suggest the assumed low seismic hazard potential of this area needs serious reconsideration.

Geological, Geomorphological and Archaeoseismological Observations Along the Cibyra Fault and Their Implications for the Regional Tectonics of SW Turkey

In this paper, the Cibyra segment of the Fethiye-Burdur Fault Zone (FBFZ) is investigated using direct field evidence, which helps clarify the controversial behaviour of this zone. The remains of the ancient city of Cibyra which is located on the Cibyra Fault provide invaluable data in documenting traces of fault deformations and related palaeoearthquakes. Slickensides on fault planes, deflected stream beds and terraces, fault-parallel elongated ridges along the Cibyra Fault are the clearest surface evidence for left-lateral faulting. Archaeoseismological evidence in the ancient city is consistent with the geological and geomorphological observations along the fault. Based on detailed field observations, it can be concluded that the Cibyra Fault reactivated in AD 417 and probably after the 7th century AD, causing extensive damage in Cibyra. Based on geological and geomorphological field evidence, fault offsets and deformed archaeological relics, it can be suggested that the Cibyra Fault is an active left-lateral fault capable of producing earthquakes of considerable magnitude. Furthermore, as the trend of the Cibyra Fault is consistent with the FBFZ it is concluded that NNE-SSW-trending faults in southwestern Turkey are active and the motion on them is left lateral.

Late cenozoic stress field in the Cameli Basin, SW Turkey

A history of deformation has been determined for the Cameli Basin located in the western part of the major Fethiye–Burdur Fault Zone, interpreted as the on-land continuation of Pliny–Strabo fault system (e.g., eastern boundary of the Hellenic Arc). Inversion of fault slip vectors affecting Mio-Pliocene to Quaternary formations in the Cameli Basin, in the southwestern segment of the transtensional Fethiye–Burdur Fault Zone, yields two different normal faulting stress regimes characterized by a roughly orthogonal set of extensional axes; a NW–SE (N129 ± 19 °E) σ 3 axis and a NE–SW (N50 ± 16 °E) σ 3 axis. The orientation of fault sets is predominantly around the NE–SW direction in the major Fethiye–Burdur Fault Zone, making the extension NW–SE. The mean R values are 0.74 and 0.69 for both extensions indicating a triaxial stress state, which is clearly different from radial extension and from transitional to strike-slip stress state. The NW–SE extension is probably responsible for the formation of the Cameli Basin during Mio-Pliocene time. In contrast, the inversion of focal mechanism solutions of shallow earthquakes occurring within the Cameli basin identifies a present-day, predominantly extensional stress regime, characterized by an approximately N–S (N184 °E) σ 3 axis, which has an R value of 0.637 indicating a triaxial stress state. The nearly orthogonal extensional stress regimes seem to have been acting contemporaneously with each other at different intensities from the Mio-Pliocene onwards in SW Turkey. This may be attributed to the geodynamic effects related to the subduction of the African plate beneath Anatolia, diffusing along Hellenic and Cyprus arcs and in the west-southwestward extrusion of Anatolia. Our hypothesis is that the cause of the early NW–SE extension is the slab-pull force due to the subduction process along the Cyprus arc, considered to be dominant up to Plio-Quaternary. The later NE–SW to present-day ∼ N–S extension, dominant since the Plio-Quaternary, is related to the combined forces of the Anatolian extrusion and the subduction process along the Hellenic arc.

A VLF survey using current gathering phenomena for tracing buried faults of Fethiye–Burdur Fault Zone, Turkey

Fethiye–Burdur Fault Zone (FBFZ) produces moderate to large earthquakes which can severely affect the surrounding cities spreading towards the basins of the region. In this study, with the aim of feature city planning, very low frequency electromagnetic (VLF) survey was carried out across (FBFZ) to locate subsurface faults covered by basin fills. VLF parameters such as the apparent resistivity, phase (VLF-R response) real and imaginary parts of tipper (VLF-EM response) were obtained using GBZ, a well known radio station in England at Oxford, which give a strong signal in our survey area with a suitable frequency (19.6 kHz) for our purposes. VLF method is called as VLF-EM, when it is only relying on the measurement of horizontal and vertical magnetic fields. However, when it includes measurement of horizontal electric field, providing resistivity values, it is referred as VLF-R method. In this study, the direction of horizontal electric field is perpendicular to fault strike describing the H-polarization mode. Although this mode produces strong VLF-R (resistivity) response, we also obtained quite clear and characteristic VLF-EM anomalies along some of the survey profiles. Both VLF-R and VLF-EM responses with the contribution of the vortex and gathered (direct) currents, in E and H-polarization modes, are reviewed and VLF anomalies observed over FBFZ are discussed. In FBFZ, current gathering anomalies become stronger in the presence of high conductivity contrast and in the presence of parallel fault branches separating the medium into resistors in series. In these conditions, changing electrical charge at the contacts of faults cause successive variations in E-field. As a result VLF-R response is strengthened and also secondary magnetic field which causes VLF-EM anomalies may be enhanced, in H-polarization mode. Interpretation of resistivity, phase and tipper data with current density pseudosections, over our survey lines, showed the location of buried faults of FBFZ beneath the sedimentary covers of the basins.

From palaeotectonics to neotectonics in the Neotethys realm: The importance of kinematic decoupling and inherited structural grain in SW Anatolia (Turkey)

In order to asses young, i.e. “neotectonic” fault kinematics and the relation with plate-tectonic processes in SW Turkey we focused on the questions: 1) what produced the structural grain, i.e. how and when are faults generated, 2) what was/is the kinematic behaviour of these faults and 3) during which period(s) were these faults active? Firstly, the distribution of faults has been investigated using a lineament analysis performed on satellite imagery and digital elevation models. We define five main tectonic domains in SW Turkey: 1 and 2) the Northern and Southern Western Anatolian extensional provinces; 3) the eastern Hellenic arc (including Rhodes Island and the submarine Anaximander mountains); 4) The Lycian Taurides and 5) the western limb of the Isparta Angle. Lineament analysis reveals dominance of three lineament groups, i.e. NNE-, ENE-, and WNW-trending, in all identified domains. Variations in the relative importance of lineament groups exist and are attributed to the specific tectonic evolution of each domain. A synthesis of recently published field data shows that the onset of activity of related fault groups is neither synchronous, nor uniform. The “structural grain” for the neotectonic deformation in SW Turkey is formed during the last stage of palaeotectonic deformation (stage 1), which is dominated by the onset of the Menderes Massif exhumation along a top-N major detachment, the Datça break-away fault [Seyitoğlu, G., Işık, V., and Çemen, İ., 2004. Complete Tertiary exhumation history of the Menderes massif, western Turkey: an alternative working hypothesis. Terra Nova, 16, 358–364.], and related SE-ward sliding of the Lycian Nappes in the footwall of this fault. This stage is characterized by spatially variable types of deformation that are delineated by, from NW to SE, the Datça Fault around the Menderes–Lycian contact zone and the Lycian frontal thrust zone, respectively. The kinematic decoupling along these structures explains the co-existence of top-N detachment type extension in the Western Anatolian Extensional province and ongoing nappe emplacement and piggy-back development in the Lycian Taurides. The decoupling also explains the lateral complexity of deformation associated with later neotectonic deformation. From late Miocene onward, stage 2 NNE–SSW extension dominated the Western Anatolian Extensional province, influenced by combined Anatolian extrusion and Hellenic subduction roll-back. Contemporaneously, bidirectional ESE–WNW and NNE–SSW extension controls the Lycian Taurides due to the effects of Hellenic arc expansion superposed on extrusion-roll-back extension. The zone of kinematic decoupling is characterized by structural complexity, with local transpressional features. During stage 3 (post-Late Pliocene), the same types of extension prevail in the Western Anatolian Extensional province and the Lycian Taurides, although a third tectonic regime becomes gradually more important. This regime is associated with a tectonic escape in the Hellenic arc that induced forearc slivers to be sheared of the expanding arc along (mostly) sinistrally displacing ENE-trending strike-slip zones. Several of these zones have been identified in the coastal zones of SW Turkey, either through recent seismicity or field observations and are especially focused in the Lycian Taurides domain. Here, they form what is classically referred to as the Fethiye–Burdur Fault Zone, which becomes gradually penetrated from the SW by oblique- or strike-slip zones, exemplifying the time-transgressive nature of the tectonic escape mechanism. Zones of kinematic decoupling remain persistent throughout the entire Early Miocene–Recent tectonic evolution of SW Turkey and explain the existence of differently deforming tectonic domains.

Different stress states in the Burdur–Isparta region (SW Turkey) since Late Miocene times: a reflection of a transient stress regime

The Burdur–Isparta region is a transitional zone between two distinct neotectonic domains in Turkey: the Burdur graben system as the northeastern part of the Fethiye–Burdur fault zone and the Kovada graben at the apex of the Isparta angle. Each domain represents a particular stress regime. Fault data from unconsolidated Pliocene and Quaternary deposits were combined with stress states deduced from pre-Pliocene consolidated rocks in order to reconstruct the stress field evolution in the study area since Late Miocene. Different stress states were identified. They were put in a stratigraphic framework and U/Th dating of fault-related calcite precipitates proved to be an additional tool in constraining the history of the stress states. The reconstructed history reflects a transient stress regime. The evolving stress field indicates that the influence of the Kovada stress regime fades through time and that the influence of the Burdur stress regime is gaining importance, suggesting a northeastwards progression of the Fethiye–Burdur fault zone.

Neotectonic development of the Çameli Basin, southwestern Anatolia, Turkey

Abstract This study of the Çameli Basin presents a detailed basin evolution combined with structural analysis and provides the first detailed time-stratigraphic framework for the neotectonic development of Neogene grabens along the Fethiye-Burdur Fault Zone in southwestern Anatolia. During the Early Tortonian, the Çameli Basin was established as a broad fault-bounded fluviolacustrine basin that experienced NW-SE extension. By Mid-Pliocene time, continued NW-SE extension resulted in the formation of a new intrabasinal fault zone that split the basin longitudinally into two compartments. The development of a new generation of normal faults further split the basin into four narrow half-graben compartments at the end of the Late Pliocene. Structural analysis of basin-bounding and intrabasinal faults related to this three-stage basin development shows that NW-SE extension apparently persisted from Late Miocene to early Quaternary time. The youngest (i.e. Holocene), deformation is characterized by dextral shear along NE-SW-trending strikeslip faults and continuing NW-SE extension. The Late Miocene foundering of the basin was related to extension in the northerly hinterland zone of the still-emplacing Lycian nappes, whereas outward growth of the Hellenic Arc in response to the westward Anatolian extrusion is the main cause for NW-SE extension from the Pliocene onward. Dextral strike-slip faulting is localized and is associated with the activity of NW-SE-trending faults that accommodated NE-SW extension. The simultaneous activity of these faults suggests the existence of biaxial extensional tectonics, as initially proposed for the Burdur-Dinar area. Sinistral strike-slip faulting, continuing along the eastern Hellenic Arc, penetrated the southernmost part of Turkey but has not yet reached the Çameli Basin area. Our biostratigraphically well-constrained tectonosedimentary model for the evolution of the Çameli Basin provides a reliable time-stratigraphic framework for NE-SW extension in the ‘Fethiye-Burdur Fault Zone’ of SW Anatolia. We believe that this fault zone represents a broad zone of isolated or interconnected NE-SW-trending basins that formed under prevailing NW-SE extension, rather than being a significant strike-slip fault zone.

Magnetotelluric images of the crust and mantle in the southwestern Taurides, Turkey

Inversion of the magnetotelluric data across the southwestern Taurides reveals two subzones of crust with varying thicknesses: conductive lower crust (<75 Ω m), overlain by resistive (>350 Ω m) upper crust, with four resistive cores (>2000 Ω m) separated by three relatively conductive vertical zones. The first and second vertical zones coincide with surface faults interpreted in Anatolia, such as Fethiye Burdur Fault Zone. The third one is the most conductive and lies in continuity with the Strabo Fault Zone in the Mediterranean Sea. A hypocentral cross section of earthquakes along the profile shows more dense seismic activity in the second resistive core where the conductive crust is not present beneath it. The depth of the crust/upper mantle boundary varies between 30 and 50 km and has an undulating character. The resistivity of the upper mantle reaches 500–1000 Ω m.

The Deep Resistivity Structure of Southwestern Turkey: Tectonic Implications

Magnetotelluric data along two profiles, across the Lycian nappes and the Beydag autochthon of the southwestern Taurides in the eastern Mediterranean region images shallow and deep crustal structures. Inversion of the magnetotelluric data from profiles K and H reveals two subzones of the crust of varying thickness; the first is the conductive and viscoelastic lower crust (< 75 ohm m), whereas the second is the resistive (500-7500 ohm m) and brittle upper crust. The thickness of the uppermost conductive units, the Lycian nappes, is found to be 3.5-4 km in the northwest and 0.5 km in the southeast. The total thickness of the autochthon that forms the resistive upper crust varies from 7-16 km beneath the Lycian nappes to 11-20 km beneath the Korkuteli region along profile K. The depth to the upper/lower crust boundary varies from 10 to 30 km in the region. The resistive upper crust is interrupted by more conductive vertical zones. One of these zones along profile K coincides with the Fethiye Burdur fault zone (FBFZ), one of the most prominent geological structures in the region. The FBFZ lies in continuity with the Pliny and the Strabo subduction zones in the Mediterranean Sea. Projections of all the vertical resistivity discontinuities in the MT images onto the gravity map with the main surface faults show an alignment parallel to the FBFZ, and the Pliny and the Strabo trenches. The Bouguer gravity map shows a low gravity zone between the towns of Fethiye and Burdur. This gravity low also coincides with the alignment of projections of vertical high conductivity zones onto the map. Almost no earthquakes occur in the conductive lower crust, whereas significant earthquakes occur in the resistive upper crust, and the resistive lithospheric upper mantle (~250 ohm m) in the southeastern part of the region along the profile K. In contrast, in the northwestern part of the profile, the upper mantle is conductive (80 ohm m), indicating a viscoelastic character.

The Anaximander Mountains: a clue to the tectonics of southwest Anatolia

AbstractThe offshore Anaximander Mountains are an important link between the Hellenic and Cyprus arcs. They were formed by southeastward rifting from Turkey in post‐Miocene time. Gravity data have shown that the eastern part of the Anaximander Mountains is different from the western part; multibeam mapping seems to confirm that the eastern Anaximander Mountains have affinity with the Florence Rise structure (western Cyprus Arc). Faulting along and across the latter feature is characterized in the seismic data by anastomosing faults and pop‐up flower structures. It is likely that progressive adjustment to incipient collision developed into a broad zone of NW–SE transpressive wrenching extending towards south Turkey. In contrast, the western mountains are more directly related to the opening of the Rhodes Basin and the Finike Basin, as transtension may have dominated in southwest Turkey since the Pliocene. The connection with onshore Turkey is still unclear, but could be related to the Fethiye–Burdur Fault Zone that defines the western boundary of the complex Isparta Angle. The Anaximander Mountains and the Isparta Angle form together a tectonic accommodation zone between the active deformation in southwestern Turkey and the Aegean region and the tectonically quieter Cyprus region. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Active tectonics of the Eastern Mediterranean region: deduced from GPS, neotectonic and seismicity data

This paper reviews the main tectonic features of the Eastern Mediterranean region combining the recent information obtained from GPS measurements, seismicity and neotectonic studies. GPS measurements reveal that the Arabian plate moves northward with respect to Eurasia at a rate of 23 ± 1 mm/yr, 10 mm/yr of this rate is taken up by shortening in the Caucasus. The internal deformation in Eastern Anatolia by conjugate strike-slip faulting and E-W trending thrusts, including the Bitlis frontal thrust, accommodates approximately a 15 mm/yr slip rate. The Northeast Anatolian fault, which extends from the Erzincan basin to Caucasus accommodates about 8 ± 5 mm/yr of left-lateral motion. The neotectonic fault pattern in Eastern Anatolia suggests that the NE Anatolian block moves in an E-ENE direction towards the South Caspian Sea. According to the same data, the Anatolian-Aegean block is undergoing a counter-clockwise rotation. However, from the residuals it appears that this solution can only be taken as a preliminary approximation. The Eulerian rotation pole indicates that slip rate along the North Anatolian fault is about 26 ± 3 mm/yr. This value is 10 mm/yr higher than slip rates obtained from geological data and historical earthquake records and it includes westward drift of the Pontides of a few millimetres/year or more. GPS measurements reveal that the East Anatolian fault accommodates an 11 ± 1 mm/yr relative motion. GPS data suggest that Central Anatolia behaves as a rigid block, but from neotectonic studies, it clearly appears that it is sliced by a number of conjugate strike-slip faults. The Isparta Angle area might be considered a major obstacle for the westward motion of the Anatolian block (Central and Eastern Anatolia). The western flank of this geological structure, the Fethiye-Burdur fault zone appears to be a major boundary with a slip rate of 15-20 mm/yr. The Western Anatolian grabens take up a total of 15 mm/yr NE-SW extension. The fact that motions in Central Anatolia relative to Eurasia, are 15-20 mm/yr while in Western Anatolia and Aegean Sea they are 30-40 mm/yr could suggest that Western Anatolia decouples from Central Anatolia and the Isparta Angle by the Fethiye-Burdur fault zone and Eski?ehir fault. It is also hypothesized that the differentiation of tectonic styles and velocities in the Anatolian-Aegean block are related to differences between the slabs lying under the Cyprus and Hellenic arcs.