Yazar "Balkaya, Caglayan" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • [ X ]
    Öğe
    Delineation of shallow resistivity structure in the city of Burdur, SW Turkey by vertical electrical sounding measurements
    (Springer, 2009) Balkaya, Caglayan; Kaya, M. Ali; Goektuerkler, Goekhan
    The city of Burdur, which is built on an alluvium aquifer, is located in one of the most seismically active zones in southwestern Turkey. The soil properties in the study site are characterized by unconsolidated and water-saturated sediments including silty, clayey and sandy units, and shallow groundwater level is the other characteristic of the site. Thus, the city is under soil liquefaction risk during a large earthquake. A resistivity survey including 189 vertical electrical sounding (VES) measurements was carried out in 2000 as part of a multi-disciplinary project aiming to investigate settlement properties in Burdur city and its vicinity. In the present study, the VES data acquired by using a Schlumberger array were re-processed with 1D and 2D inversion techniques to determine liquefaction potential in the study site. The results of some 1D interpretations were compared to the data from several wells drilled during the project. Also, the groundwater level map that was previously obtained by hydrological studies was extended toward north by using the resistivity data. 2D least-squares inversions were performed along nine VES profiles. This provided very useful information on vertical and horizontal extends of geologic units and water content in the subsurface. The study area is characterized by low resistivity distribution (< 150 Omega m) originating from high fluid content in the subsurface. Lower resistivity (3-30 Omega m) is associated with the Quaternary and the Tertiary lacustrine sediments while relatively high resistivity (40-150 Omega m) is related to the Quaternary alluvial cone deposits. This study has also shown that the resistivity measurements are useful in the estimation of liquefaction risk in a site by providing information on the groundwater level and the fluid content in the subsurface. Based on this, we obtained a liquefaction hazard map for the study area. The liquefaction potential was classified by considering the resistivity distributions from 2D inversion of the VES profiles, the types of the sediments and the extended groundwater level map. According to this map, the study area was characterized by high liquefaction hazard risk.
  • [ X ]
    Öğe
    Exploration for a cave by magnetic and electrical resistivity surveys: Ayvacik Sinkhole example, Bozdag, Izmir (western Turkey)
    (Soc Exploration Geophysicists, 2012) Balkaya, Caglayan; Gokturkler, Gokhan; Erhan, Zulfikar; Ekinci, Yunus Levent
    Geophysical survey techniques have been successfully applied to near-surface cave detection in karstic terrains. We used magnetic and electrical resistivity surveys to delineate the karstic structure of the Ayvacik Sinkhole, which may be considered to be a vertical cave. The magnetic-total-field-anomaly map helped reveal the metamorphic and sedimentary units in the study area. The total-horizontal-gradient map, which was based on a calculated pseudogravity anomaly, successfully identified the contact between the limestone unit and the cave system. Using these results, we positioned and carried out a vertical electrical sounding (VES) survey with a Schlumberger array along a line that consisted of 11 stations. The VES data were then processed using a ID global optimization technique, which used a genetic algorithm and a 2D linearized least-squares algorithm. The results were generally in good agreement with each other, and together they pointed out three geologic layers: (1) an overburden layer (>316 Omega m), (2) an approximately 25-m-thick alluvial fill (100-316 Omega m), and (3) a limestone unit (316-3162 Omega m); and also suggested the existence of a high-resistive anomaly (>15000 Omega m), possibly a karstic cave, located at the depth of approximately 40 in. Also, the results suggested that the buried limestone unit had an undulating karstic topography including a probable pinnacle structure. A synthetic modeling study was carried out, and it validated the reliability of the results. Finally, our findings indicated that the geophysical survey techniques used here were successful in detecting a cave located deep enough to make human exploration difficult.
  • [ X ]
    Öğe
    Geomagnetic and geoelectrical prospection for buried archaeological remains on the Upper City of Amorium, a Byzantine city in midwestern Turkey
    (Oxford Univ Press, 2014) Ekinci, Yunus Levent; Balkaya, Caglayan; Seren, Aysel; Kaya, Mehmet Ali; Lightfoot, Christopher Sherwin
    On the basis of geophysical imaging surveys, including geomagnetic and geoelectrical resistivity, possible archaeological remains and their spatial parameters (i.e., location, extension, depth and thickness) were explored to provide useful data for future excavations on the Upper City of the ancient Amorium site, which comprises a large prehistoric man-made mound. The surveys were performed very close to the main axis of the Basilica, and the derived geophysical traces indicated some subsurface structures that appear to confirm that more-substantial brick and masonry buildings lie near the present-day surface of the mound. Analyzing the local gradients by total horizontal derivatives of pseudogravity data enhanced the edges of the magnetic sources. Additionally, a profile curvature technique, which has rarely been applied to potential field data sets, dramatically improved the magnetic-source body edges and the lineaments that may be associated with buried archaeological remains. The depths of these possible anthropogenic remains were estimated by applying the Euler deconvolution technique to the geomagnetic data set. The Euler solutions on tentative indices indicated that the depths of the source bodies are not more than about 3 m. Moreover, geoelectrical resistivity depth slices produced from the results of two- and three-dimensional linearized least-squares inversion techniques revealed high-resistivity anomalies within a depth of about 3 m from the ground surface, which is in close agreement with those obtained by applying the Euler deconvolution technique to the magnetic data. Based on the existence of some archaeological remains in the vicinity of the surveyed area, these geophysical anomalies were thought to be the possible traces of the buried remains and were suggested as targets for excavations. This study also emphasized that the data-processing techniques applied in this investigation should be suitable for providing an insight into the layout of the unexcavated parts of the Amorium site.