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    3D Modeling and Tectonic Interpretation of the Erzincan Basin (Turkey) using Potential Field Data
    (UNIV NACIONAL DE COLOMBIA, 2019) Aydin, Omer L.; Bektas, Ozcan; Buyuksarac, Aydin; Yilmaz, Huseyin
    Erzincan Basin was investigated using gravity data within the scope of this study. It is also aimed to reveal the discontinuities in the work area as well as the buried discontinuities. Boundary determination filters and analysis of the structure of the data and its connection are revealed and clear information is obtained. Gravity anomalies were applied with an upward continuation method for 0.25, 0.50, 0.75 and 1 km levels. Total Horizontal Derivative (THD) filter, Analytical Signal (AS) filter, Tilt Angle Derivative (Tilt) filter, Total Horizontal Derivative (THDR) filter, Theta Angle Derivative (Cos theta) filter, Hyperbolic Tilt Angle Derivative (HTAD) were applied to upward continued data. The discontinuities in the region and the boundaries of the geological structure were revealed. Tilt and Theta Angle derivatives yield the best results from the applied derivative based filters. The obtained data were compared with the existing surface geology and the compatibility between the formations was checked. New discontinuities were found in addition to the discontinuities determined from surface observations in the light of the obtained results. Erzincan Basin was modeled in three dimensions using gravity data of the study area. As a result of modeling, Erzincan Basin has been determined to have an average thickness of 7 km.
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    3D MODELLING AND STRUCTURAL INVESTIGATION OF THE CENTRAL VOLCANICS IN SLOVAKIA USING MAGNETIC DATA
    (NORTH UNIV BAIA MARE, 2013) Bektas, Ozcan; Buyuksarac, Aydin; Rozimant, Kamil
    The 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.
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    Achieving Intensity Distributions of 6 February 2023 Kahramanmaraş (Türkiye) Earthquakes from Peak Ground Acceleration Records
    (Mdpi, 2024) Buyuksarac, Aydin; Isik, Ercan; Bektas, Ozcan; Avcil, Fatih
    On 6 February 2023, two large earthquakes struck southern Turkiye 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.
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    Assessment of potential seismic hazard and site effect in Antakya (Hatay Province), SE Turkey
    (SPRINGER, 2011) Over, Semir; Buyuksarac, Aydin; Bekta, Ozcan; Filazi, Ahmet
    Antakya city is at risk because of strong earthquakes occurring in the area, and different soil conditions that can produce variation of the ground motion amplification. Microzonation of cities provides a basis for site-specific hazard analysis in urban settlements. In particular, seismic microzonation can be provided by means of detailed seismic assessment of the area, including earthquake recordings and geological studies. In this paper, we propose a preliminary microzonation map for the city of Antakya, based on the variation of the dominant periods and shear velocities of the sediments covering the area. The periods are retrieved from microtremor measurements conducted at 69 sites, using the horizontal-to-vertical spectral ratio technique. The results of microtremor analysis were compared with data obtained from refraction microtremor (ReMi) measurements at four profiles crossing the studied area. According to the classification of dominant periods, Antakya city can be divided into five zones, probably prone to different levels of seismic hazard. The shorter natural periods are in inner Antakya and both the sides of Asi River (i.e., northern and southern parts). The eastern and western parts of Antakya have maximum dominant periods. The V (s) (30) values were calculated by using the ReMi method along the profiles. Antakya city has V (s) (30) values in the range of category C of the national earthquake hazard reduction programme site classification.
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    Bedrock Depth Calculation of ?anakkale (Turkey) Basin Using Rayleigh Ellipticity and Microgravity Survey
    (Inst Geophysics Unam, 2023) Buyuksarac, Aydin; Eyisuren, Onur; Bektas, Ozcan; Karaca, Oznur
    It 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.
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    Crustal Structure of Turkey from Aeromagnetic, Gravity and Deep Seismic Reflection Data
    (SPRINGER, 2012) Ates, Abdullah; Bilim, Funda; Buyuksarac, Aydin; Aydemir, Attila; Bektas, Ozcan; Aslan, Yasemin
    In this paper, aeromagnetic and gravity anomalies obtained from the General Directorate of Mineral Research and Exploration were subjected to upward continuation to 3 km from the ground surface to suppress shallow effects and to expose only regional, deep sources. Then, a reduction to pole (RTP) map of aeromagnetic anomalies was produced from the 3 km upward continued data. A sinuous boundary to the south of Turkey is observed in the RTP map that may indicate the suture zone between the Anatolides and African/Arabian Plates in the closure time of the Tethys Ocean. The sinuous boundary can be correlated with the recent palaeo-tectonic maps. The southern part of the sinuous boundary is quite different and less magnetic in comparison with the northern block. In addition, maxspots maps of the aeromagnetic and gravity anomalies were produced to find out and enhance the boundaries of tectonic units. Crustal thickness, recently calculated and mapped for the western Turkey, is also extended to the whole of Turkey, and the crustal thicknesses are correlated with the previous seismological findings and deep seismic sections. The average crustal thickness calculations using the gravity data are about 28 km along the coastal regions and increase up to 42 km through the Iranian border in the east of Turkey. Density and susceptibility values used as parameters for construction of two-dimensional (2D) gravity and magnetic models were compiled in a table from different localities of Turkey. 2D models indicate that all of the anomalous masses are located in the upper crust, and this could be well correlated with the earthquakes which occurred at shallow depths.
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    Estimating shear wave velocity using acceleration data in Antakya (Turkey)
    (UNIV NACIONAL DE COLOMBIA, 2014) Buyuksarac, Aydin; Over, Semir; Genes, M. Cemal; Bikce, Murat; Kacin, Selcuk; Bektas, Ozcan
    This manuscript presents a site response analysis and an estimation of S-wave velocity that are dependent on acceleration data. First, existing data, such as density, seismic wave velocity, and soil cross-sections, are obtained from previous seismic microzonation studies and used to prepare input data for a suite of MATLAB routines, which are referred to as SUA software. Acceleration data are obtained from four free-field strong-motion stations of the SERAMAR project, which was conducted between 2006 and 2009 in conjunction with a Turkish-German joint research project, and inputted into the software as basic data. The results include a 1D velocity cross-section versus depth and an amplification model of the site. Three different depth levels can be determined for the ranges of 0-5 m, 5-15 m and 15-25 m. The seismic velocities vary between 380 and 470 m s-1 for the first 5 m; 320 and 480 m s-1 for 5-15 m; and 470 and 750 m s-1 for 15-25 m. These results are comparable with the amplification values from the microtremor data from previous studies. The 1D velocity models are appropriate for the soil conditions.
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    Evaluation of Gravity and Aeromagnetic Anomalies for the Deep Structure and Possibility of Hydrocarbon Potential of the Region Surrounding Lake Van, Eastern Anatolia, Turkey
    (SPRINGER, 2014) Aydemir, Attila; Ates, Abdullah; Bilim, Funda; Buyuksarac, Aydin; Bektas, Ozcan
    The North Anatolian Fault (NAF) is not observed on the surface beyond 40 km southeast of Karliova town toward the western shoreline of Lake Van. Various amplitudes of gravity and aeromagnetic anomalies are observed around the lake and surrounding region. In the gravity anomaly map, contour intensity is observed from the north of Mus city center toward Lake Van. There is a possibility that the NAF extends from here to the lake. Because there is no gravity data within the lake, the extension of the NAF is unknown and uncertain in the lake and to the east. Meanwhile, it is observed from the aeromagnetic anomalies that there are several positive and negative amplitude anomalies aligned around a slightly curved line in the east-west direction. The same curvature becomes much clearer in the analytic signal transformation map. The volcanic mountains of Nemrut and Suphan, and magnetic anomalies to the east of the Lake Van are all lined up and extended with this slightly curved line, provoking thoughts that a fault zone that was not previously mapped may exist. The epicenter of the major earthquake event that occurred on October 23, 2011 is located on this fault zone. The fault plane solution of this earthquake indicates a thrust fault in the east-west direction, consistent with the results of this study. Volcanic mountains in this zone are accepted as still being active because of gas seepages from their calderas, and magnetic anomalies are caused by buried causative bodies, probably magmatic intrusions. Because of its magmatic nature, this zone could be a good prospect for geothermal energy exploration. In this study, the basement of the Van Basin was also modelled three-dimensionally (3D) in order to investigate its hydrocarbon potential, because the first oil production in Anatolia was recorded around the Kurzot village in this basin. According to the 3D modelling results, the basin is composed of three different depressions aligned in the N-S direction and many prospective structures were observed between and around these depressions where the depocenter depths may reach down to 10 km.
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    Failure mechanism by wrench faulting in Central Anatolia
    (Pergamon-Elsevier Science Ltd, 2024) Buyuksarac, Aydin; Gundogdu, Erdem; Bektas, Ozcan; Isik, Ercan
    The study area, where volcanism and tectonism are active at the same time, consists of the Cappadocia Volcanic Complex (CVC) in the middle, Tuzgol & uuml; on the west side, and Ecemis, 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 Tuzgol & uuml; and Ecemis, 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 Tuzgol & uuml; Fault (-30 degrees) dipping counterclockwise and the Ecemis, Fault, clockwise (60 degrees) 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.
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    Fault modeling around southern Anatolia using the aftershock sequence of the Kahramanmaras earthquakes (Mw=7.7 and Mw=7.6) and an interpretation of potential field data
    (Springer Int Publ Ag, 2024) Buyuksarac, Aydin; Bektas, Ozcan; Alkan, Hamdi
    On February 6, 2023, southeastern Turkiye experienced devastating doublet earthquakes (Mw = 7.7 and Mw = 7.6) with a series of aftershocks along the East Anatolian Fault Zone. The mainshocks were followed by similar to 15,000 aftershocks mainly distributed in the NNE-SSW direction, including similar to 400 events with an Mw >= 4.0 in the following 30 days. Although many moderate to large earthquakes have occurred in the historical and instrumental periods of this region, these double earthquakes and their aftershocks majorly impacted lives and released great seismic energy. In this study, we interpret the gravity-magnetic data and the epicenter and hypocenter distributions of the aftershocks to correlate the tectonic structures and the active fault zones. The results of potential field anomalies reveal that the rotational anomalies in the southwestward direction are associated with the tectonic structure of Anatolia. Results show that shallow aftershocks are associated with high-gravity anomalies, whereas deeper aftershocks are associated with low-gravity anomalies and they become shallower in places where gravity values increase. After the derivative transformations are applied to the magnetic anomalies, it is seen that the faults and regions of magnetic discontinuity are in good agreement. Consequently, the findings on gravity, magnetic anomalies and aftershock sequences demonstrate that the first mainshock occurred in the unbroken segment of the East Anatolian Fault Zone.
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    Geophysical analysis of fault geometry and volcanic activity in the Erzincan Basin, Central Turkey: Complex evolution of a mature pull-apart basin
    (PERGAMON-ELSEVIER SCIENCE LTD, 2016) Akpinar, Zafer; Gursoy, Halil; Tatar, Orhan; Buyuksarac, Aydin; Kocbulut, Fikret; Piper, John D. A.
    The Erzincan Basin is one of several Neogene sedimentary basins developed by prolonged right-lateral strike-slip along the North Anatolian Fault Zone (NAFZ), the intracontinental transform defining the present boundary between the Eurasian Plate to the north and accreted Anatolian terranes to the south. The basin has a strong asymmetry and young (<780 ka) volcanic centers with widespread development of cross faults defining an advanced phase of pull-apart basin evolution. To isolate faults with no surface geomorphic or morphotectonic signatures in the young sedimentary cover, continuous magnetic profiles were conducted together with detailed interpretation of the regional Bouguer gravity map. This geophysical approach combined with surface mapping defines a fault geometry highlighting a series of buried structures including a fracture system 0.2-2.35 km wide which conforms to the volcanic lineaments seen at the surface. A model is developed for the evolution of the Erzincan Basin with a history commencing as a simple pull-apart by right-lateral strike-slip on the developing NAFZ, probably in Early Pliocene times. Subsequent interaction with a major left-lateral (Ovacik) fault (OF) caused the focus of motion on the NAFZ to shift to the southwest and develop a complex fishbone fracture system. This became the focus of volcanic activity on three lineaments which migrated progressively southwards toward the axis of the basin. Continuing motion on the OF transformed the south east margin of the basin into an extensional zone and the tectonic history of the basin has been further complicated by its proximity to a major transform intersection between the NAFZ and OF. The signatures of recent volcanism and the development of cross faults on which much activity is now concentrated define a mature pull-apart advancing toward extinction. (C) 2015 Elsevier Ltd. All rights reserved.
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    Geophysical investigation and hydrocarbon potential of Cankiri-Corum Basin, Turkey
    (ELSEVIER SCIENCE BV, 2013) Aslan, Yasemin; Buyuksarac, Aydin; Erik, Nazan Yalcin; Aydemir, Attila; Ates, Abdullah
    The Cankiri-Corum Basin is one of the larger, onshore sedimentary basins in central Turkey. In this paper, the integration of geophysical data and geological findings in the Cankiri-Corum Basin was performed and they both present a complex basin structure. In the frame of geophysical study, two-dimensional (20) models were constructed using gravity and magnetic anomalies. Seismic sections were interpreted and correlated with the 2D models using the borehole data as control. Basement depth, basin geometry and sources for magnetic anomalies along the 20 model profiles were determined in integration of seismic, gravity, aeromagnetic and borehole data. Seismic section CC-L-1 is correlated with the Topuzsaray-1 well. Tuffs and volcanic units penetrated in this well might be correlated across a reverse fault close to the borehole. Seismic sections, CC-L-2 and CC-L-3, are consistent with the gravity models at the deeper parts of the sections. On the other hand, there are inconsistencies in the shallow sections with the gravity models due to unexpected velocity variations in both the horizontal and vertical directions. The average depth of basement was found to be about 5 km by means of gravity modelling, which was correlated with the seismic sections. Magnetic anomalies are represented by intense values in the NW portion of the study area, but they indicate very low intensities in the middle of the map. A reverse magnetised body to the north of the study area was modelled in 2D along a profile and it was interpreted that this body might be an ophiolitic remnant. Polarities of many anomalies to the south and northeast of the region indicate remanent magnetisation. Alignment of the polarities extends in the northwest direction, indicating that the region rotated in the anticlockwise direction. Because there is around a 5 km sedimentary basin fill in the study area, it may exhibit hydrocarbon potential and the Yesilcat oil seep evidences this potential. Surface samples were collected to examine source rock potential and to correlate with the Yesilcat seep by analysing the organic geochemical properties. In this study, 72 samples were collected from different formations and it was found that the Yoncali Formation displays better source rock potential than the other formations studied. (C) 2013 Elsevier B.V. All rights reserved.
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    Geophysical Investigation of Mount Nemrut Stratovolcano (Bitlis, Eastern Turkey) Through Aeromagnetic Anomaly Analyses
    (Springer Basel Ag, 2020) Ekinci, Yunus Levent; Buyuksarac, Aydin; Bektas, Ozcan; Ertekin, Can
    Quaternary Mount Nemrut stratovolcano, having a spectacular summit caldera and associated lakes, is located north of the Bitlis-Zagros suture zone, Eastern Turkey. Although much attention has been paid to its geology, morphology, history and biology, a detailed geophysical investigation has not been performed in this special region. Thus, we attempted to characterize the stratovolcano and the surroundings using total field aeromagnetic anomalies. Potential field data processing techniques helped us to interpret geologic sources causing magnetic signatures. Resulting image maps obtained from some linear transformations and a derivative-based technique revealed general compatibility between the aeromagnetic anomalies and the near-surface geology of the study area. Some high amplitude magnetic anomalies observed north of the Nemrut caldera rim are associated with the latest bimodal volcanic activity marked by lava fountains and comenditic-basaltic flows occurred along the rift zone. After minimizing the high-frequency effects, a pseudogravity-based three-dimensional inversion scheme revealed that the shallowest deep-seated sources are located about 3.0 km below the ground surface. Two-dimensional normalized full gradient solutions also exposed the depths of these anomaly sources, in good agreement with the inversion results. This first geophysical study performed through aeromagnetic anomalies clearly gave insights into some main magnetized structures of the Mount Nemrut stratovolcano.
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    Images of buried graves in Bayat, Afyon (Turkey) from high-resolution magnetic data and their comparison with preliminary excavations
    (ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2007) Arisoy, M. Ozgu; Kocak, Ozdemir; Buyuksarac, Aydin; Bilim, Funda
    Dedemezari necropolis, the site of our study, is located in the west of Turkey near Afyon. Archaeologists think that it belongs to the Middle Bronze age. A high-resolution magnetic survey identified buried material highly accurately. In particular, anomalies, which are transformed by the analytic signal method, clarify the observed magnetic anomalies. Magnetic surveying was applied in three different areas in this study. The map of analytic signal-transformed anomalies presented good results on preliminary excavation in trenches A and B. Two types of graves are found in the study area. One is made of clay and the second is carved in the rocks. Shapes of the buried graves are mainly cylindrical and elliptical. Most of the magnetic anomalies are elliptical and reflect the shape of the buried materials. Future excavations in Dedemezari necropolis will be able to be carried out more easily due to the known locations of the buried graves. (c) 2006 Elsevier Ltd. All rights reserved.
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    Interpretation of Magnetic Anomalies and Estimation of Depth of Magnetic Crust in Slovakia
    (SPRINGER BASEL AG, 2009) Rozimant, Kamil; Buyuksarac, Aydin; Bektas, Oezcan
    The magnetic map of Slovakia used in the paper was compiled as part of a project titled Atlas of Geophysical maps and profiles in 2001. The residual magnetic data were analyzed to produce Curie point estimates. To remove distortion of magnetic anomalies caused by the Earth's magnetic field, reduction to pole transformation was applied to the magnetic anomalies using the magnetization angle of the induced magnetization. Anomalies reduced to the pole tend to be better correlated with tectonic structures. We applied a 3-km upward continuation to the residually compiled magnetic anomalies in order to remove effects of topography. The depth of magnetic dipoles was calculated by an azimuthally averaged power spectrum method for the entire area. Such estimates can be indicative of temperatures in the crust, since magnetic minerals lose their spontaneous magnetization according to Curie temperature of the dominant magnetic minerals in the rocks. The computed Curie point depths in the Slovakia region vary between 15.2 km and 20.9 km. Heat flow higher than 100 mWm(-2) occurs at the central volcanics and eastern part of Slovakia, where the Curie point depths values are shallow. The correlation between Curie point depths, heat flow and crust depth was investigated for two E-W cross sections. Heat flow and Curie point depth values are correlated with each other however, these values could not be correlated with crust depth. The Curie point isotherm, which separates magnetic and non-magnetic parts of the crust, is represented in two cross sections.
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    Investigation into the regional wrench tectonics of inner East Anatolia (Turkey) using potential field data
    (ELSEVIER SCIENCE BV, 2007) Buyuksarac, Aydin
    The residual aeromagnetic and gravity anomalies of inner East Anatolia, surveyed by the Mineral Research and Exploration (MTA) of Turkey, display complexities. Some faults, which are known and new lineaments, are drawn from maxspot map derived from the location of the horizontal gradient of gravity anomalies. Tectonic lineaments of inner East Anatolia exhibit similarities to the direction of East Anatolian Fault Zone. Anticlockwise rotation, approximately -30 degrees, defined from disorientations of aeromagnetic anomalies. The lineaments obtained from maxspots map produced from the gravity anomalies and disoriented aeromagnetic anomalies are in-line with the mobilistic system revealed by the palaeomagnetic data. These Alpine age continental rotations caused westward wrenching of the global lithosphere and led to significant tectonic reactivation and deformations. GPS measurements, current tectonic knowledge and the results of the evaluation of potential field data were combined in a base map to demonstrate similarities. (c) 2006 Elsevier B.V. All rights reserved.
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    Investigation of earthquake sequence and stress transfer in the Eastern Anatolia Fault Zone by Coulomb stress analysis
    (Tubitak Scientific & Technological Research Council Turkey, 2024) Alkan, Hamdi; Buyuksarac, Aydin; Bektas, Ozcan
    A devastating earthquake with a magnitude of (M-w = 7.7) occurred on February 06, 2023, in the Pazarcik 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 (M-w = 7.6) occurred in Ekinozu-Elbistan (Kahramanmaras) in the northwest. Three more earthquakes with magnitudes of M-w = 6.6, M-w = 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 M-w = 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 Elazig and Malatya in the northeast, Kahramanmaras-Goksun 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 (similar to 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.
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    Investigation of magnetic surveying data of buried grave jars in Harmanoren Necropolis (Turkey) using linear transformations and analytic signal
    (ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2006) Buyuksarac, Aydin; Bilim, Funda; Ates, Abdullah; Bektas, Ozcan
    Harmanoren Necropolis is the third biggest excavated necropolis in southwest Anatolia, dating back to 2500 B.C. The individual burials are composed of ceramic jars. The dead bodies were placed in the fetal position in buried grave jars which were elongated eastwards. Buried burnt ceramics can be located by their own magnetic field directions. Thus, magnetic surveying was used in the Harmanoren Necropolis in three different areas to locate buried grave jars ahead of archaeological excavation. Magnetic anomalies present some results, but to identify these as buried grave jars, advanced spectral methods were applied to the magnetic anomalies. Polarity orientations of magnetic anomalies are different from a north-south direction due to remnant magnetization. 'Reduction to the pole' transformation could not entirely remove disoriented polarities arising from the effect of remnant magnetization. 'Analytic signal' transformation minimizes the disorientation caused by the effect of remanence. Magnetic susceptibility measurements of samples from the excavated jars indicate that the observed magnetic anomalies could be caused by them. A good correlation was observed between the processed magnetic anomalies and excavation results. (c) 2005 Elsevier Ltd. All rights reserved.
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    Investigation of the deep structure of the Sivas Basin (innereast Anatolia, Turkey) with geophysical methods
    (ELSEVIER SCIENCE BV, 2008) Onal, K. Mert; Buyuksarac, Aydin; Aydemir, Attila; Ates, Abdullah
    Sivas Basin is the easternmost and third largest basin of the Central Anatolian Basins. In this study, gravity, aeromagnetic and seismic data are used to investigate the deep structure of the Sivas Basin, together with the well seismic velocity data, geological observations from the surface and the borehole data of the Celalli-1 well. Basement depth is modeled three-dimensionally (3D) using the gravity anomalies, and 2D gravity and magnetic models were constructed along with a N-S trending profile. Densities of the rock samples were obtained from the distinct parts of the basin surface and in-situ susceptibilities were also measured and evaluated in comparison with the other geophysical and geological data. Additionally, seismic sections, in spite of their low resolution, were used to define the velocity variation in the basin in order to compare depth values and geological cross-section obtained from the modeling studies. Deepest parts of the basin (12-13 km), determined from the 3D model, are located below the settlement of Hafik and to the south of Zara towns. Geometry, extension and wideness of the basin, together with the thickness and lithologies of the sedimentary units are reasonably appropriate for further hydrocarbon exploration in the Sivas Basin that is still an unexplored area with the limited number of seismic lines and only one borehole. (c) 2008 Elsevier B.V. All rights reserved.