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Öğe 3D modelling and structural investigation of the central Volcanics in Slovakia using magnetic data(2013) Bektaş, Özcan; Büyüksaraç, Aydin; Rozimant, KamilThe Central volcanics, located in central part of Slovakia, is characterized by intense andesitic volcanic activity that resulted in the formation of stratavolcanoes and dome complexes of Middle and Late Miocene age. The basement area has been affected tectonically resulting in the formation of horst and graben structures. The Central Slovakian Volcanic Field (CSVF) exhibits a very complex magnetic anomaly. A 3-km upward continued magnetic map indicates a deep-seated source for this magmatism. The pseudogravity transformation of the upward continued anomaly has also been constructed. This anomaly was modelled by a 3D-method. The anomalous body lies between the depths of 4.4 to 8.5 km beneath the surface of the CSVF. Volcanic structures and some lineaments are presented on the maxima of the horizontal gradient of the pseudogravity anomaly map. They are well correlated with the structural map of CSVF.Öğe Achieving Intensity Distributions of 6 February 2023 Kahramanmaraş (Türkiye) Earthquakes from Peak Ground Acceleration Records(MDPI, 2024) Büyüksaraç, Aydın; Işık, Ercan; Bektaş, Özcan; Avcıl, FatihOn 6 February 2023, two large earthquakes struck southern Türkiye on the same day, resulting in a considerable loss of life and property damage over a large region that included 11 cities. After these disasters, there was a requirement to define the soil-related intensity distribution, aside from manufacturing defects caused by buildings. The modified Mercalli intensity (MMI) scale results in the same intensity value (XI) when decimal values are not mathematically considered, even though the fundamental data in the AFAD and USGS sources differ. In this study, an equation based on the MMI–PGA relationship was obtained and tested with ten previously developed equations to calculate the earthquake intensity. Seven of these selected equations, depending on the earthquake magnitude, were calculated comparatively. The equation most compatible with the earthquakes that occurred on 6 February 2023 was obtained in this study. In addition, it was decided that three similar equations could also be used. Intensity distribution maps were created according to the calculated MMI values. In this way, it has been observed that different earthquake intensity values are more sensitive, reliable, objective, and sustainable.Öğe Archaeo-geophysical Investigations in Ahlat Seljuk Square Cemetery, Bitlis, Eastern Anatolia TURKIYE(2023) Büyüksaraç, Aydın; Kulaz, Mehmet; Bektaş, Özcan; Dumankaya, Oktay; Ekinci, Yunus Levent; Koşaroğlu, SinanGeophysical methods are frequently used in archaeological sites to obtain significant priori information. These methods assist archaeological excavation strategies by indicating the anomaly zones that may be associated with buried remains. Archaeo-geophysical methods are based on measuring the physical parameter contrast (e.g. magnetic susceptibility, dielectric constant, resistivity, density) between the buried archaeological remains and the covering environment. In this study, magnetic and ground penetrating radar methods were applied to contribute to excavation planning. The study area is a historical cemetery and has been used as an interment area for about 1000 years. Considering the information obtained from the previous excavations, the research depth was initially planned not to exceed 3 meters in general, but information up to 10 meters was obtained. We aimed at determining possible graves in the area outside the walls of Square Cemetery in Ahlat (Bitlis) district. After performing some data-processing steps to the raw data obtained, magnetic and ground penetrating radar anomaly maps were produced. Based on the distinguishable geophysical traces most promising locations were determined and suggested for archaeological excavations.Öğe Bedrock Depth Calculation of Çanakkale (Turkey) Basin Using Rayleigh Ellipticity and Microgravity Survey(Universidad Nacional Autonoma de Mexico, 2023) Büyüksaraç, Aydın; Eyisüren, Onur; Bektaş, Özcan; Karaca, ÖznurIt is a well-known fact that the local ground effect plays an important role in the damage to structures during earthquakes. In order to define the soil-structure interaction correctly, the geometry of the tight and loose soil layers in the soil should be well known. In addition, the impedance contrast due to local ground effects can be deeper than the first 30 m, which is accepted as the engineering depth, and in this case, the Vs,30 parameter is disabled. For this reason, the location of engineering bedrock and seismic bedrock gains importance. The variation of shear wave velocity with depth is a key parameter for seismic field effect estimation. In addition, the separation of low-density layers close to the surface and higher-density bedrock can be easily done by the gravity method. Bedrock/seismic foundation levels were determined by using these two methods together for canakkale soils, which are known to have thick alluvial thickness and liquefaction problems. Microgravity measurements were made at 100 points and the anomalies obtained were modelled in three dimensions. In light of the data obtained from this study, it has been determined that the thickness of the loose basin unit in the study area is in the range of about 50-300 m. Ambient vibration was recorded with the help of a velocity seismometer at 146 points, and S velocity (Vs) profiles were obtained by using the inversion of the observed ellipticity curve. In addition, the velocity-depth change rate structure of the basin is defined depending on the Vs velocities on the 2D gravity model made along the two profiles that cut the basin in N-S and E-W directions. Along these profiles, the frequency range has been determined as 0.8-1.3 Hz in the deep parts of the Basin and 1.5-11.0 Hz in the shallow parts.Öğe Coulomb Stress Analysis in Nemrut Caldera (East Anatolia, Türkiye)(2024) Alkan, Hamdi; Bektaş, Özcan; Büyüksaraç, AydınIn volcanic areas, seismic events with low energy occur before seismic activity or due to the movement observed in the magma. These earthquakes, which are caused by the expansion-contraction movement that has been revealed in different studies and is mostly observed in the magma chamber, can be recorded with continuous observations. On the other hand, it is not easy to distinguish between tectonic and volcanic origins of earthquakes occurring in volcanic areas. In this study, Coulomb stress analysis was carried out using earthquakes in the Nemrut Stratovolcano, which is located in the eastern Türkiye and is at the westernmost end of a volcano arc, and it was concluded that the stress is related to the Nemrut Caldera, therefore the positive stress caused by the expansion of the magma chamber of the Nemrut Volcano creates tremors.Öğe Determination of historical graves by ground penetrating radar method: Sakarya Field Battle (August 23-September 13, 1921, Turkey)(Taylor and Francis Ltd., 2021) Koşaroğlu, Sinan; Kamacı, Züheyr; Erdoğan, Selim; Bektaş, Özcan; Büyüksaraç, AydınThe Sakarya Field Battle was the last phase of the forward operation of the Greek Asia Minor Army, which started at the end of March 1921. Although there are contradictory numbers regarding the losses of the parties in the Sakarya Field Battle in the literature, it is generally accepted that the Turkish Army lost 5,713 martyrs. The Ground Penetrating Radar (GPR) method was applied to determine the accuracy of findings observed on the surface and to determine burial sites. Geophysical anomalies were detected in 2D profiles from the obtained results. It was determined that the Turkish side buried the martyrs in east-west direction, depending on their religious traditions. The detected anomalies were evaluated in two and three dimensions and the boundaries of the burial areas and the approximate depths of the burials were obtained. The results obtained from data processing techniques showed that the GPR method is suitable for determining the locations of historical graves on battlefields. The new martyrs found as a result of the studies are thought to be soldiers whose fate was unknown, recorded as 'missing' in the records.Öğe Failure mechanism by wrench faulting in Central Anatolia(Elsevier Ltd, 2024) Büyüksaraç, Aydın; Gündoğdu, Erdem; Bektaş, Özcan; Işık, ErcanThe study area, where volcanism and tectonism are active at the same time, consists of the Cappadocia Volcanic Complex (CVC) in the middle, Tuzgölü on the west side, and Ecemiş fault systems on the east side. Remote sensing image processing method and derivation to aeromagnetic data were applied to identify the structural lineations that tectonically control the study area within the scope of the study. As a result of the lineation analysis performed in the west of the study area, 167 lineaments in the west, most of which are NW oriented, and 316 lineaments, most of which are NE oriented, were determined in the east. These findings are in agreement with the known fault orientations in the area. It is known that earthquakes greater than M > 4 occurred in these known faults during the neotectonics period, and they also have the potential to produce M > 6 earthquakes. In addition, the Tuzgölü and Ecemiş Faults' shearing effect relative to each other is an indication that a wrench tectonics mechanism has developed in the study area. With the remote sensing study and following the existing surface traces, two fault systems in opposite directions, the Tuzgölü Fault (−30°) dipping counterclockwise and the Ecemiş Fault, clockwise (60°) dipping, were determined. The orientation and locations of the faults could be determined by tilt transformation applied to the magnetic anomaly map of the study area. In particular, the effects of wrenching in the study area can be clearly observed in magnetic anomalies.Öğe Importance of Bedrock Depth Knowledge in Basins: Çanakkale (Dardanalles) Case History(Springer Science and Business Media Deutschland GmbH, 2022) Büyüksaraç, Aydın; Karaca, Öznur; Eyisüren, Onur; Bektaş, Özcan; Işık, ErcanIt is not correct to produce the necessary information for structuring, especially in environments such as Çanakkale, which exhibit a basin structure, without determining the bedrock or the strict ground conditions in bedrock. This approach is the basis of earthquake resistant building design. In this study, which was carried out to determine the bedrock/seismic foundation depth for the central settlement of Çanakkale and to define the basin structure to a certain extent, microgravity measurements were taken on a large scale, and the study area was modelled in three dimensions based on the obtained gravity data. By taking long-term microtremor measurements, one-dimensional depth-shear wave (Vs) velocity models were obtained using the Rayleigh ellipticity method. A depth map of the engineering bedrock was created, in which the velocity Vs reached to 2500 m/s. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Öğe Investigation of earthquake sequence and stress transfer in the Eastern Anatolia Fault Zone by Coulomb stress analysis(TUBITAK, 2024) Büyüksaraç, Aydın; Alkan, Hamdi; Bektaş, ÖzcanA devastating earthquake with a magnitude of (Mw = 7.7) occurred on February 06, 2023, in the Pazarcık segment of the Eastern Anatolian Fault Zone, which has not shown major earthquake activity for a long time. On the same day, another earthquake with a magnitude of (Mw = 7.6) occurred in Ekinözü-Elbistan (Kahramanmaraş) in the northwest. Three more earthquakes with magnitudes of Mw = 6.6, Mw = 5.9, and ML = 5.7 occurred on the same day, and significant damage, loss of life, and property occurred in 11 provinces and districts. A sixth earthquake occurred with Mw = 6.4 magnitude in Defne-Hatay on February 20, 2023. In addition, more than 32,000 aftershocks were recorded while this study was in progress. The interconnection of these earthquakes was investigated by Coulomb stress analysis. It showed compatibility with the distribution of both these six earthquakes and small aftershocks, in which earthquakes transfer stress to each other during their formation phases. By calculating Coulomb stress changes, mainshock ruptures have played an important role in transferring stresses between Elazığ and Malatya in the northeast, Kahramanmaraş-Göksun in the west, and Hatay and Syria in the south. Also, our calculations showed that shallow depths in and around source zones received positive stress changes (~1.0 bar) due to the focal depths of mainshocks with their aftershocks. Finally, it has been better understood with these earthquakes that the stress transfer time of high-energy earthquakes can be shortened considerably.Öğe Investigation of Site Characterization and Vulnerability in Antakya (Turkey) under Basin Effect(2023) Büyüksaraç, Aydın; Bektaş, Özcan; Işık, Ercan; Över, Semir; Kaçın, SelçukIt is very important and necessary to know the depth of the bedrock in determining the soil behavior. However, determining the depth of bedrock spatially is a very difficult and costly process. The depth of the bedrock can be obtained by using the dominant vibration frequency obtained by the microtremor data. The bedrock depth map was created with the correlation produced from the dominant vibration frequencies obtained from microtremor measurements made in Antakya (Turkey). In bedrock calculations at low frequencies, the value range shows scattering. In the vulnerability analysis for Antakya soils, a low level of vulnerability (Kg = 6) was obtained in the east and northeast of the area. It has been observed that the S-wave velocity (Vs) in this area is lower than 406 ms-1. In this case, this value has been accepted as the vulnerability threshold value in Antakya soils. Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) were obtained for each location by using earthquake ground motion levels with 2%, 10%, 50%, and 68% probability of exceedance in 50-year periods. The PGA values in the region range from 0.43 to 0.47 g for earthquakes with a return period of 475 years.Öğe THE CAESAREA GERMANICIA (?) OF ARCHEOGEOPHYSICAL INVESTIGATIONS(2022) Dumankaya, Oktay; Bektaş, Özcan; Koşaroğlu, Sinan; Büyüksaraç, AydınThe remains unearthed in the Dulkadiroğlu district, one of the central districts of Kahramanmaraş, are thought to belong to Caesarea Germanicia, which was founded in the Roman Period. Research and excavations carried out by the Kahramanmaraş Museum and us in the region have revealed that the spread of archaeological cultural remains is more than 150 hectares. Although the concentration of Roman Period cultural remains in the research and excavations was remarkable, the discovery of Byzantine, Seljuk, and Ottoman Period ceramic pieces indicates an uninterrupted settlement in the research area for centuries. However, as can be seen in the images, the dense residential texture in the region is one of the biggest obstacles to archaeological research and excavations. Because, in order to carry out archaeological excavations of the identified structures, expropriations are required. However, the expropriation period covers an average of 2-4 years, which makes it difficult to conduct scientific research. Archeogeophysical methods provide information about the location, depth, and dimensions of the archaeological remains by applying them from the surface, without causing any damage to the archaeological remains sought. In this context, Ground Penetrating Radar (GPR) measurements were carried out to determine the quality of the mosaic-based structure on 445 layout, which were previously unearthed through illegal excavations in 2019, and the parcels on which it extends. GPR was carried out along 6 profiles. The obtained results were compared both with each other and with the existing surface conditions, and GPR depth maps were created. When the GPR depth sections were examined, 4 important reflections were found. It has been interpreted that 3 of these reflections belong to the archaeological building remains and 1 of them originates from a metal material (pipe). It was determined that the depth of the archaeological remains identified in the GPR sections started at a depth of approximately 20 cm. As a result of the excavation, it was seen that the reflections determined in the GPR sections belonged to the wall remains and metal pipe. As a result of archaeological excavations, it was determined that the GPR reflections belong to the remains of the walls of the Villa Rustica of the Early Byzantine Period or a Roman bath, as well as a metal pipe. In the measurements of the ground radar, it was determined that other walls cut the building walls in parallel. As a result of archaeological excavations, it was understood that these walls were made of rubble stone with mud additives. It was discovered during archaeological excavations and was discovered in the 11th-13th centuries AD. One of the ceramic fragments indicates that this structure was used again in the Middle Byzantine Period.
