Alper Demirci

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...

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.

An active extensional deformation example: 19 May 2011 Simav earthquake (Mw = 5.8), Western Anatolia, Turkey

The Simav Earthquake that occurred on 19 May 2011 in western Turkey was investigated on the basis of seismological data and geological observations. Approximately WNW?ESE trending surface ruptures were observed on the Simav Fault. The focal mechanism parameters of the earthquake (Mw = 5.8) and its aftershocks (Mw??>??3.5) were estimated using time-domain moment tensor inversion. A total of 2245 events were located with Geiger?s conventional absolute location method then relocated using the double difference (DD) algorithm. The calculated locations at a depths between 2 and 16?km were found to be consistent with Coulomb stress variation in the area. Average variance reduction (VR) of the solutions was calculated as ~70%. The focal parameters of strike dip and slip of the main shock, occurring at a depth of 11?km dipping towards the NNE, were estimated at 277, 62 and ?92, respectively. The most striking indication of the study is that the area is dominated by normal faults with mainly WNW?ESE trends. It is also concluded that earthquakes in the region are caused by an active and regional NNE?SSW (N 12? E) trending (?3 axis) extension regime. The mean stress ratio is 0.80, indicating a triaxial stress state. This extension is probably associated with a slab?pull force and /or roll-back due to the complex subduction process of the African Plate beneath Anatolian block along both the Hellenic and Cyprus arcs in the eastern Mediterranean region.

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.