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- MakaleYalnız künye2024Edge detection and depth estimation of Lake Sapanca, Eastern Marmara Region, from high-resolution magnetic data
Aktaş, Gülten
The present study aims to determine submarine structural elements by analysing high-resolution magnetic data sets and to examine the impact of geological surface structures characterizing Lake Sapanca. Lake Sapanca is located on the northern branch of the North Anatolian Fault Zone. The study area and its immediate surroundings are located within the most active tectonic structure of Turkey. A magnetic study was carried out in Sapanca Lake to reveal the structural elements that caused the formation of the lake. Diurnal corrections were applied to the magnetic data. During the analysis of the marine magnetic data set, there are variations in the mean field level of the magnetic field caused by the routing effects of ship noise on the measurements. To eliminate this noise effect, directional correction was performed. Then, de-stripping correction was also applied. It is essential to estimate the boundaries and depths of the structural features of the region. In order to elucidate the structural features of the region, different techniques such as tilt angle derivative, the total horizontal derivative of tilt angle derivative, Euler 2D deconvolution, horizontal gradient magnitude, and source edge detection were applied to magnetic data. 2-D modelling using GM-SYS in Oasis Montaj were performed. These techniques identified and mapped the edges of anomalous sources related to magnetic data corresponding to geological elements in the study area. The results allow us to image the submarine lineaments for the survey area. These structural lineaments are in E–W, NE–SW and NW–SE trends. These lineaments in our results are quite compatible with the faults in previous geophysical results. The E–W trending lineaments are related to the E–W trending faults in the region.
- MakaleYalnız künye2023Interpretation of the tectonic structure of Gemlik Bay using magnetic data
Aktaş, Gülten; Hisarlı, Z. Mümtaz; Demirel, A. Sinan
The aim of this study was to determine the effects of the main faults and many small-scale faults and submarine structures within Gemlik Bay, on the middle strand of the North Anatolian Fault in the southeast of the Sea of Marmara. In order to produce a fault map for the study area and research tectonic structures, magnetic data were obtained using a cesium vapor magnetometer on a total of 30 profiles (340 km) with N-S and E-W orientation within the bay. Diurnal corrections were applied to obtain the necessary minimization of diurnal variations in the magnetic data. Heading correction and micro-leveling corrections were applied to remove small boat effects, and the reduction to the pole method was applied for greater differentiation of the magnetic data. Magnetic data were analyzed using advanced potential field processing techniques. Euler deconvolution technique was applied to define the extension and depth of the determined lineaments. Boundaries of structures in the region were determined using source edge detection, tilt derivative, the tilt angle of the total horizontal gradient amplitude (TAHG), and a novel edge detector based on the softsign function (SF) techniques. In order to reveal the tectonic evolution of Gemlik Bay, the structures obtained from the analysis results were interpreted and a fault map was produced. The results of the study identified the Armutlu Fault in the north, the Gemlik Fault in the east, the Zeytinbağı Fault and Mudanya Fault in the southwest and the Gençali Fault in the south within Gemlik Bay. These five essential faults significantly affected the region tectonically. These faults correlated well with the location of some previously-known major tectonic structures. Moreover, these important faults following the morphology of the bay indicate that Gemlik Bay was opened by a pull-apart basin mechanism.
- MakaleYalnız künye2023Hydrocarbon reservoir depth identification in the eastern black sea basin: Implications from euler deconvolution and gravity tensor invariants
Doğru, Fikret; Maden, Nafiz
The Black Sea Basin (BSB) consisting of Eastern Black Sea (EBS) and Western Black Sea (WBS) basins which separated by the Mid Black Sea High (MBSH) is formed by the collision of Eurasia and Arabian-African Plates. Petroleum and gas hydrate contents of the BSB have been discussed by using different geological and geophysical research. In this study, the gravity gradient tensor and invariant data based on the Bouguer gravity anomaly of the EBS basin were evaluated to define the hydrocarbon reservoirs. Afterwards, Euler deconvolution technique is applied to the invariant to reveal the depth of subsurface bodies. Furthermore, the significant invariant anomalies are compared with known oil seepage and petroleum wells. The depth values of oil trace closest to the known Sürmene and Hopa drill holes were computed as 4809 m, and 4455 m according to the structural index values of SI = 2.
- MakaleYalnız künye2021High-resolution total field magnetic anomaly maps of Lake İznik (NW Turkey): assessment of faults which play important roles in tectonics of the lake
Aktaş, Gülten; Hisarli, Z. Mümtaz; Demirel, A. Sinan
In total, 380 km of marine magnetic data were processed and interpreted to reveal the main tectonic elements that control the formation of the lake. Lake İznik, which is an approximately rectangular-shaped active tectonic basin with 32 km length and 12 km width, is located between two segments of the North Anatolian Fault in the northeast Marmara region, Turkey. The purpose of this study is to identify the tectonic elements that played a role in the formation of Lake İznik with the help of new magnetic data and to reveal the tectonic evolution of the region by using other previously collected geophysical data. The Euler deconvolution, tilt angle, analytic signal and source edge detection methods were applied to the total field magnetic data for Lake İznik and its surroundings to determine the boundaries and depths to the source of magnetism. From the structural map obtained as a result of the review of this data, linearity in the magnetic data was detected along the NW–SE direction in the north of Lake İznik, N–S direction in the west and east, and E–W direction in the south. These lineaments were correlated with a limited amount of seismic data obtained from previous studies and were associated with faults. This linearity in NW–SE direction in the north was evaluated as the continuation of the Orhangazi fault and it is thought to play a significant role in the tectonic evolution of Lake İznik. When the results obtained from this study and the paleomagnetic results for the Eocene volcanic rocks in the study area are evaluated together, Lake İznik was connected with Gemlik Bay and the Marmara Sea during the Eocene–Pleistocene and Orhangazi Fault disconnected Lake İznik from Gemlik Bay in the Pleistocene–Holocene. It was deduced that the lake basin is a pull-apart basin developed up to the present day.