REGIONAL HEAT-FLOW IN WESTERN ANATOLIA USING SILICA TEMPERATURE ESTIMATES FROM THERMAL SPRINGS

Regional trends of variation of heat flow in western Anatolia have been outlined using the silica temperature estimator on thermal springs. Silica heat-flow values from 187 springs have been calculated. The data are corrected for local long-term mean annual surface temperature. A mean value of heat flow for the western part of Anatolia of 107 +/- 45 mW m(-2) has been obtained, which is about 60% above the world average

The importance of topographic corrections on magnetotelluric response data from rugged regions of Anatolia

Topographic irregularities cause some distortions of magnetotelluric (MT) fields. In the vicinity of a topographic feature, the TM-mode distortion increases with the height and inclination of the slope. It is well-known that TM-mode (E(perpendicular to)) topographic effects are much greater than TE-mode (E(parallel to)) distortions

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 in), whereas the second is the resistive (500-7500 ohm in) and brittle upper crust. The thickness of the uppermost conductive units, the Lycian nappes, is found to be 3.5-4 kin in the northwest and 0.5 kin in the southeast. The total thickness of the autochthon that forms the resistive upper crust varies from 7-16 kin beneath the Lycian nappes to 11-20 kin 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 NIT 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 (similar to250 ohm in) 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 in), indicating a viscoelastic character

Geoelectromagnetic and geothermic investigations in the Ihlara Valley geothermal field

The Ihlara Valley is situated within a volcanic are that is formed by the collision of the eastern Mediterranean plate system with the Anatolian plate. In this study we will present data from a reservoir monitoring project over the Ihlara-Ziga geothermal field, located 22 km east of Aksaray, in central Anatolia

Magnetotelluric data in western Turkey: Dimensionality analysis using Mohr circles

During the summer of 1996, wideband (0.003125-2000 s) magnetotelluric (MT) data were collected from 52 sites across western Turkey, with a site spacing of similar to 5 km. The extensional regime is dominant as a result of the convergence of the African and Arabian plates against the Eurasian plate, and western Turkey is characterized with east-west oriented, "continental escape" tectonics. To contribute to the knowledge of the geological structures along the profile, the dimensionality characteristics of the MT impedance tensors are computed, taking real and imaginary parts of the tensor elements separately. The rotationally invariant parameters of central impedance (d(3)) and anisotropy angle (lambda) are also computed, the two being good dimensionality indicators. Pseudosections of these parameters reveal the presence of major geological structures in western Turkey, such as the zone between the Menderes Massif and the Bornova Flysch zone, the Izmir-Ankara Suture zone, the western part of the North Anatolian fault zone, and grabens (Demirci, Gordes, and Bigadic), which are the characteristic of the region. Interpretation of the full set of Mohr circles shows a strong anisotropy and high central impedance anomalies, while changes are shown in geological strike direction at estimated depths of about 7-8 km, 15-20 km, and 35-40 km along the profile from south to north. These anomalies are indicative of changes in the thickness of upper crust