Browsing by Author "Sengul, M. Alper"

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Deformation Patterns in the Van Region (Eastern Turkey) and Their Significance for the Tectonic Framework
(Slovak Acad Sciences Geological inst, 2019) Sengul, M. Alper; Gurboga, Sule; Akkaya, Ismail; Ozvan, Ali
The area of investigation is located on the south-eastern shore of Lake Van in Eastern Turkey where a destructive earthquake took place on 23rd October. 2011 (Mw =7.1). Following the earthquake, different source mechanisms, deformations, and types of faulting have been suggested by different scientists. In this research, Edremit district and vicinities located on the southern side of Van have been investigated to understand the deformation pattern in a travertine (400 ka) formation on the surface, and its structural and stratigraphic relationships with the main faults under the surface by using two-dimensional (2D) Electrical Resistivity Tomography (ERT) profiles. The results were used to document the deformation pattern of rocks with the Miocene and the Holocene (400 ka travertine) in ages. By means of the investigations, deformation patterns implying the tectonic regimes during the Oligocene-Miocene-Pliocene, and Quaternary time have been determined. According to detailed field work, the local principal stress direction has been defined as approximately N35 degrees W. This is also supported by the joint set and slip-plane data. Moreover, Oligocene-Miocene units provide a similar principal stress direction. Our data suggest that the southern part of the Elmalik fault is characteristic of reverse faults rather than of the normal fault system that has been previously reported. In addition, the Gurpinar fault controlling the deformation patterns of the region is a reverse fault with dextral component.
Determining the Site Effects of 23 October 2011 Earthquake (Van Province, Turkey) on the Rural Areas Using Hvsr Microtremor Method
(indian Acad Sciences, 2015) Akkaya, Ismail; Ozvan, Ali; Tapan, Mucip; Sengul, M. Alper
A magnitude of 7.1 Mw earthquake struck Van city on October 23, 2011. Although, construction practices of all rural housing units are similar in the region, the earthquake caused massive damage to villages located on soft soils in northern region of the city. In this study, the effects of soil conditions on damaged housing units were determined by conducting horizontal to vertical spectral ratios of microtremor (HVSR) measurements. The level of damage in the villages that are settled on lacustrine and stream sediments has verified that the damage correlates well with comparatively high HVSR peak period and HVSR peak amplitude values in the range of 0.2-1.6 s and 4-10, respectively. The HVSR peak period and HVSR peak amplitude levels on rock units are in the range of 0.1-0.2 s and 1.5-2, respectively. It is important to note that hillside effect is found to be another key factor that increased the level of damage to the housing units in some villages.