Yazar "Cakir, Ozcan" seçeneğine göre listele

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    A potential landslide area investigated by 2.5D electrical resistivity tomography: case study from Canakkale, Turkey
    (Springer Heidelberg, 2016) Coskun, Nart; Cakir, Ozcan; Erduran, Murat; Kutlu, Yusuf Arif; Cetiner, Ziya Sedat
    Geophysical methods provide important tools to investigate the shallow earth. One of these methods is electrical resistivity tomography (ERT), which has the capability to provide spatial and volumetric information on both subsurface structures and property variations. Specifically, the ERT is an important tool to define the geometry and characteristics of landslides. In this study, we share our results for an electrical resistivity tomography survey that we conducted on a field where the city of Canakkale, Turkey has a plan to build a War Museum approximately 56 acres wide. The construction field under consideration presents potential landslide risks prominent with high slopes on especially the northeastern side of the area. Because of possible intense load on the ground anticipated from deployment of heavy artillery and also from construction sites, landslide risks in the field are significantly increased. Quaternary-aged alluvial formations consisting of unconsolidated clastic sediments cover the region. In order to investigate the area, we carried out 2.5-dimensional resistivity survey using a multi-channel, multi-electrode system along 16 profiles with a total length of 2016 m. Borehole information from ten close wells was used to aid the interpretation of resistivity sections. The results showed that the shallow electrical structure beneath the study area is multi-layered of which the second layer from the top has the lowest resistivity and then the resistivity values steadily increase with depth. The low resistivity in the second layer is likely caused by extra water injection into the system from relatively high topographic structures to the southeast and also from nearby water channel that partly perimeters the study area. The bottom of low resistivity layer exhibits potential landslide surface overriding the deeper slate bedrock with relatively high resistivity. The excess load after the planned construction may trigger catastrophic slip along this slip interface. Based on our observations, we proposed some protective measures to avoid the landslides in the considered area.
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    Öğe
    Perturbation method to compute 1-D anisotropic P and S receiver functions
    (Elsevier, 2013) Cakir, Ozcan
    We propose a new algorithm to compute the teleseismic P and S receiver function synthetics for a multilayered Cartesian structure with anisotropic flat layers. The algorithm is based on the first-order perturbation theory in which the layered background structure is assumed one-dimensional with isotropic variations in vertical direction. Anisotropic velocity perturbations acting as secondary sources constitute the heterogeneities in the medium. The total wavefield is solved using a convolutional type integral equation along with the Green's function of the one-dimensional reference medium extracted using the reflectivity method. The integral equation involves a five-fold integration in space and wavenumber domains. Four of these integrals are achieved analytically and the fifth integral, which is spatial integral in the vertical direction, is performed numerically for which the Born single scattering approximation greatly suffices. The proposed algorithm is demonstrated on some selected numerical examples adapted from published work in the literature. (C) 2013 Elsevier B.V. All rights reserved.
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    Preliminary investigation of underground settlements of Nevsehir Castle region using 2.5-D electrical resistivity tomography: Cappadocia, Turkey
    (Springer Heidelberg, 2016) Coskun, Nart; Cakir, Ozcan; Erduran, Murat; Kutlu, Yusuf Arif; Yalcin, Ali
    The Nevsehir Castle region located in the middle of Cappadocia with approximately cone shape is investigated for the existence of an underground city using the geophysical method of electrical resistivity tomography. Underground cities are commonly known to exist in Cappadocia. The current study has obtained important clues that there may be another one under the Nevsehir Castle region. Several 2.5-D resistivity profiles totaling approximately 4 km in length surrounding the Nevsehir Castle are measured to determine the distribution of electrical resistivities under the study area. Several high resistivity anomalies with a depth range 8-20 m are discovered to associate with a systematic void structure beneath the Nevsehir Castle. Because of the high-resolution resistivity measurement system currently employed, we were able to isolate the void anomalies from the embedding structure. Using 3-D visualization techniques, we show the extension of the void structure under the measured profiles.