Yunus Levent Ekinci

Characterization of a Landslide using Seismic Refraction, Electrical Resistivity and Hydrometer Methods, Adatepe – Çanakkale, NW Turkey

Seismic refraction and electrical resistivity surveys were carried out to characterize a landslide that occurred near the Canakkale-Lapseki-Bursa highway, in northwest Turkey. Hydrometer analyses were also performed to highlight the composition of the slip surface material. The combined interpretation of the methods yielded the mass of the landslide body and the possible subsurface nature of a basal slip plane. Sediment-size fraction maps show that the slip surface material contained an excessive amount of clay. The clay-rich slipping layer was observed to a maximum depth of 4–5 m marked by a low (2–4 ohm‐m) resistivity zone, contrasting with the underlying sand-rich beds with relatively higher resistivities (<6 ohm‐m) . A velocity variation ranging between ∼1,250–1,500 m∕s also characterized this water-saturated slipping zone. Results indicated a buried failure surface under the studied shallow slide mass, which appeared to be a prolongation of the long upward-concave slip surface of the old landslide ar...

A geophysical approach to the igneous rocks in the Biga Peninsula (NW Turkey) based on airborne magnetic anomalies: geological implications

The Biga Peninsula, the complex geological structure of which has attracted intense attention so far, is located in the north-western part of Anatolia, Turkey. The Peninsula is tectonically very important region where different tectonic zones meet and comprises various kinds of sedimentary, metamorphic and igneous rocks. Among these rocks, igneous rocks occupy a considerably amount of areas in the Biga Peninsula and they are mostly associated with geothermal systems and mineral deposits, and therefore they play an important role in the geology of the Peninsula. In this paper, derived results concerning the geological features and subsurface structures of the igneous rocks in the Peninsula are presented based on analyzing the airborne magnetic anomalies. To this end, a MATLAB-based toolkit named as Gravity and Magnetic Interpretation (GMINTERP) that is composed of a set of linked functions in conjunction with a graphical user interface was developed and used for the interpretation of the airborne magnetic anomalies. Some linear transformations and derivative-based techniques were performed to process the potential field data-set and also to help build a general understanding of the geological details. The close agreement between the derived geophysical anomaly maps and the well-known surface geology map of the Biga Peninsula helped us discuss the geological implications of the geophysical traces. This study also indicated that the developed interactive data processing toolkit may assist geological interpretation even in the areas whose subsurface structure is poorly known.

On the effectiveness of directional derivative based filters on gravity anomalies for source edge approximation: synthetic simulations and a case study from the Aegean graben system (western Anatolia, Turkey)

Approximating the locations and lateral boundaries of anomalous bodies (i.e. geological structures or contacts) is an important task in the interpretation of gravity field data. Edge-approximating algorithms based on the computation of directional derivatives are widely used for enhancing the gravity anomalies of the source bodies. These algorithms effectively aid geological mapping and interpretation by locating abrupt lateral changes in density, and may also bring out subtle details in the data without specifying any prior information about the nature and type of the sources. Therefore, some model parameters of source bodies may be estimated in this way, which may guide the inverse modelling procedure. In this paper we aim to review the effectiveness of the commonly used edge-approximating algorithms such as vertical derivative, total horizontal derivative, analytic signal, profile curvature, tilt angle and theta map in terms of their accuracy on the determination of locations and lateral boundaries of source bodies. These detections were performed on both noise-free and noisy synthetic gravity data. Additionally, a real gravity data set from a well-known geological setting, the Aegean graben system (western Turkey), was considered and the derived anomaly maps were compared with known mapped geology.

Depositional Characteristics of Carbonate-Cemented Fossil Eolian Sand Dunes: Bozcaada Island, Turkey

ABSTRACT Erginal, A.E.; Ekinci, Y.L.; Demirci, A.; Avcıoğlu, M.; Öztürk, M.Z.; Türkeş, M., and Yiğitbaş, E., 2013. Depositional characteristics of carbonate-cemented fossil eolian sand dunes: Bozcaada Island, Turkey. Coastal eolianite on the south coast of Bozcaada Island, Turkey, was investigated by field observations, petrographic and climatological examinations, and electrical resistivity tomography data. The 4- to 7-m-thick eolianite, including rhizolith morphotypes characterized by root tubules and bifurcated root casts, demonstrates dune-sand accumulation during the Upper Pleistocene. Our results showed that paleowind drift and recent windblown sand drift on the island are similar. The dune sands exhibit various cement types formed of calcite and aragonite, such as micrite encrustations, meniscus and gravitational cements, and in particular, void fills. Dune-sand accumulation took place on the truncated surface of Miocene deposits. Geophysical data showed the existence of large weathered cavities within the eolianite and a high-angle normal fault, which displaces the eolianite, together with the underlying Miocene unit.

Interpretation of gravity anomalies to delineate some structural features of Biga and Gelibolu peninsulas, and their surroundings (north-west Turkey)

On the basis of gravity data, derived anomaly traces were presented for the interpretation of some shallow structural features of Biga and Gelibolu peninsulas. Since building general understanding of subtle details about subsurface geology is of great importance considering that the study area is tectonically important, some advanced data processing techniques were implemented to gravity anomalies in a detailed manner. The procedures were performed using a MATLAB-based software package (Gravity and Magnetic Interpretation – GMINTERP). First, a finite element method was utilised to produce the residual data-set which is expected to reflect short wavelength anomalies arising from shallower geological structures, and thereafter some derivative-based algorithms were executed to analyse the residual data. The general anomaly patterns obtained from the applications clearly corresponded to the well-known surface geology map of the study area. Derivative-based anomaly maps put forward some findings about the existence of an old caldera structure in the western part of the Biga Peninsula. Additionally, abrupt lateral changes in anomaly amplitudes indicated the presence of some major structural discontinuities. Thus, findings yielded to make significant geological interpretations that might be important for further investigations. This study also showed that GMINTERP software package proved useful in assisting geological interpretation using geophysical potential field data-sets.

Geophysical investigations at Agadere Cemetery, Gallipoli Peninsular, NW Turkey

Historical cemeteries are challenging targets for geophysical prospection but some non-destructive imaging techniques may be successful for mapping buried cemeteries if applied appropriately. Ground-Penetrating-Radar (GPR) has generally been considered to be the only geophysical method for determining cemeteries; however, Electrical-Resistivity-Tomography (ERT) and Magnetic-Imaging (MI), may determine geophysical traces of such cemeteries. Thus, as a first attempt at applying geophysical methods in the cemetery area of the Gallipoli Peninsula, these techniques were used to explore the buried graves at Agadere Cemetery. In this study, measured apparent resistivity data were processed using a two-dimensional (2D) tomographic inversion scheme. Resultant resistivity depth slices and volumetric resistivity images clearly showed the anomaly zone, which may be attributed to anthropogenic burials. Additionally, three-dimensional (3D) visualization of GPR results indicated some anomalies, much like the resistivity anomalies in terms of location. MI data were processed using linear transformations and an analytic signal image map presented anomaly zones located in some parts of the area, which are in agreement with those obtained by ERT and GPR surveys. Results derived from data processing techniques showed that these methods are suitable for bordering the locations of other buried historical graves in areas that have the same geological environment in the Peninsula.

Preliminary Assessment of Submerged Beachrock and Tsunamigenic Deposit, Hasır Island, Marmara Archipelago, Turkey

ABSTRACT Ertek, A.; Kılıç, E.; Erginal, A.E.; Ekinci, Y.L., and Demirci, A., 2015. Preliminary assessment of submerged beachrock and tsunamigenic deposit, Hasır Island, Marmara Archipelago, Turkey. A preassessment of coexisted submerged beachrock and a fossil-laden near-shore deposit on the coast of Hasır Island, SW Marmara Sea, is presented based on depositional characteristics, two-dimensional electrical resistivity tomography (ERT) survey and accelerator mass spectrometry (AMS) radiocarbon ages. ERT-derived geophysical images clearly showed the subsurface position and contact relationship of submerged beachrock under the studied beach. Textural features of beachrock are typical solely of marine-phreatic cementation, including consecutively developed cement fabrics, i.e. micrite coatings, radial aggregates consisting of scalenohedral high-Mg calcites, and reticulated needles of aragonite. The intertidal cementation of beachrock took place between 2940 and 2470 YBP when the level of the Marmara Sea was about 1.5 m lower than that of the present. Its purely submerged nature is likely concerned with rise in sea level in pursuit of the cementation period. Though dated between 2340 and 1590 YBP, the fossil-rich near-shore deposit behind the studied beach could be of a tsunamigenic origin based on its sequence characteristics typical of such a high-energy event.

Statistical analysis of geomagnetic field variations during the partial solar eclipse on 2011 January 4 in Turkey

Some geophysical parameters, such as those related to gravitation and the geomagnetic field, could change during solar eclipses. In order to observe geomagnetic fluctuations, geomagnetic measurements were carried out in a limited time frame during the partial solar eclipse that occurred on 2011 January 4 and was observed in Canakkale and Ankara, Turkey. Additionally, records of the geomagnetic field spanning 24 hours, obtained from another observatory (in Iznik, Turkey), were also analyzed to check for any peculiar variations. In the data processing stage, a polynomial fit, following the application of a running average routine, was applied to the geomagnetic field data sets. Geomagnetic field data sets indicated there was a characteristic decrease at the beginning of the solar eclipse and this decrease can be well-correlated with previous geomagnetic field measurements that were taken during the total solar eclipse that was observed in Turkey on 2006 March 29. The behavior of the geomagnetic field is also consistent with previous observations in the literature. As a result of these analyses, it can be suggested that eclipses can cause a shielding effect on the geomagnetic field of the Earth.

Yeni Nesil Yazılım Paketleri Kullanarak Üç-Boyutlu Görüntüleme Tekniklerinin Elektrik Özdirenç Tomografi Verilerine Uygulanması

Bu calismada, jeofizik olcumlerden elde edilen sayisal verilerin ortogonal dilimler kullanarak uc-boyutlu hacimsel goruntulenebilmesi icin gelistirilen basit bir algoritma sunulmustur. Bu algoritma dogru akim ozdirenc (DAO) yontemi ile sig derinlikte gomulu kuramsal modellerin tepkisini sunmak icin kullanilmistir. Kuramsal gorunur ozdirenc verileri iki-boyutlu ters cozum teknigiyle degerlendirilmis ve yer elektrik kesitler elde edilmistir. Sonuclar, birbirlerinden bagimsiz paralel hatlara ait iki-boyutlu yer elektrik kesitlerin bir araya getirilmesi ile olusturulan uc-boyutlu hacimsel gorunumlerle sunulmus ve model yapilara ait belirtilerin hem dusey hem de yanal yondeki surekliliklerinin tek bir sekil uzerinde kolaylikla izlenebilmesi saglanmistir. Ayrica, gelistirilen algoritma farkli ortamlarda farkli problemler icin gerceklestirilmis DAO calismalarinda elde edilen verilerin degerlendirilmesinde de kullanilmis ve yorumlamaya katki saglayan bu hacimsel goruntuler sunulmustur.

An Assessment of the Earthquakes of Ancient Troy, NW Anatolia, Turkey

According to the intermittent archeological excavations, carried out from 1871 up to the present, there exist nine different layers of settlements in Troy. Although there is some archeological evidence which indicates that some of these layers, especially Troy III (B.C. 2200‐2050) and Troy VI (B.C. 1800‐1275) have been damaged by one or more earthquakes, no multidisciplinary geoscientific research has been carried out so far on the active faults which could have caused these earthquakes.