Funda Bilim

A tectonic interpretation of the Marmara Sea, NW Turkey from geophysical data

Recent scientific investigations have revealed the deep structure and fault mechanisms in the Marmara Sea and surroundings. However, magnetic and gravity anomalies display interesting features which were not resolved in detail. In this paper, simple two-dimensional magnetic and gravity models are constructed utilizing parameters such as the density contrast and susceptibilities obtained from a borehole, seismic sections and field susceptibility measurements, respectively. The gravity model shows the existence of horst-like structures, as suggested previously. The top of the magnetic bodies in the Marmara Sea is close to the sea bottom. In general, these magnetic bodies are fault-related. The gravity model complies with the seismic base map, which was constructed previously. The magnetic anomalies of anomalous regions of the Cinarcik andWestern Basins demonstrate slight anticlockwise block rotations, while large anticlockwise block rotation is observed in the eastern extremity of the Marmara Sea. Geophysical data and modeling results suggest that the origin and evaluation of the Marmara Sea began with the possibility of emplacement of horst-like structures in the Central Ridge during the Palaeozoic or earlier followed by block rotations and intrusion of the magnetic material into the upper crust with sediment deposition and faulting. It can also be suggested that the horst-like structures in the central Marmara act to diffuse the propagation of the Northern Boundary Fault (NBF). This aspect is correlated with the focal mechanisms of the major earthquakes.

Identifying block rotations from remanent magnetization effect: Example from northern Central Turkey

One of the difficulties in interpreting magnetic anomaly data is the distortion caused by rock body magnetization. There have been several successful studies carried out on the estimation of body magnetization based on the correlation of the Bouguer and magnetic anomaly data. A number of other significant research projects have aimed at identifying the effect of remanent magnetization in magnetic data only. In this paper, we present a threedimensional method for determining the body magnetization direction by means of comparing the amplitude of the analytic signal with the horizontal gradient of pseudogravity of magnetic anomaly using the correlation coefficient equation. The method has been successfully applied to test cases and is applied here to the aeromagnetic anomalies located in northern Central Turkey. Anomalies displaying individual polarities were separated out and correlated with themselves using the correlation coefficient equation. Counter-clockwise rotations in the range of 3° and 174° were determined. Clockwise rotations were determined in the range of 19° and 153°. The inclination of the body magnetization directions for one of the blocks was estimated to be 68.4°, while all other blocks had a low inclination angle of body magnetization in the range of 32° to 57°. These results may imply that these blocks gained their magnetizations when Turkey was at low latitudes. Possible buried faults are also identified. The results reported here comply with the new mobilistic theory.

Cumhuriyet Üniversitesi, Mühendislik Fakültesi Binasının Yer Radarı (GPR) Yöntemi ile Hasarsız İncelenmesi

Yuksek frekansli Yer radari (GPR) yontemi binalarin hasarsiz incelenmesinde cok kullanisli oldugunu ortaya koymaktadir. GPR hizli, sessiz ve binada bir bozulmaya sebep olmadigi icin ozellikle tarihsel binalarin incelenmesi icin kullanisli bir yontemdir. Bu makale, Cumhuriyet Universitesi Muhendislik Fakultesi B Binasinin ana tasiyici unsurlarindan bazi perde duvarlarin Yer Radari (GPR) yontemi ile incelenmesini sunmaktadir. GPR olcumunde 1600 MHz anten kullanilmistir. Calismada, secilen perde duvarlardaki yatay ve dusey donatilarin kalinliklari, konumlari ve asinma zonlari belirlenmistir. Ayrica makale yuksek frekansli GPR yonteminin binalarin hasarsiz incelenmesinde etkisini vurgulamaktadir

Determination of block rotations and the Curie Point Depths of magnetic sources along the NW–SE-trending Sülüklü–Cihanbeyli-Gölören and Şereflikoçhisar-Aksaray Fault Zones, Central Anatolia, Turkey

The Şereflikoçhisar-Aksaray Fault (SAF) and Sülüklü–Cihanbeyli–Gölören Fault (SCGF) zones are located at the eastern and the western margins of the Salt Lake Basin-SLB (Tuzgölü Basin), central Anatolia, Turkey. These fault zones display intense magnetic anomalies along their trends and the positive amplitudes of these anomalies may reach up to 650 nT. In this paper, the body magnetisation directions are estimated from the selected five different magnetic anomalies with positive and negative peaks along these fault zones. Results of calculations indicated that local clockwise rotations are in the range of 34°E and 70°E. These magnetic anomalies were mainly created by the buried intrusive rocks. Locations of buried causative sources along the fault zones were determined from the analytic signal transformation of magnetic anomaly data. Curie Point Depths (CPDs) are also estimated from the aeromagnetic data to determine the thermal structure of the study area and they are correlated with the SAF and SCGF zones. It was found that the depth of magnetic crust varies from 11 to 22 km, consistent with the tectonic fault zones in the study area. The average value was determined as 16.7 km. These depths were correlated with the deep seismic reflection data and depths obtained from two windows in the seismic section, GTRS-87-801 are consistent with the CPDs. Shallow CPDs of magnetic sources are located along the SAF and SCGF to the east and west of the Lake Tuzgölü (Salt Lake) and it may be suggested that magnetic sources are probably located at the upper part of the crust.