Mustafa Akgün
Dokuz Eylül University
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Featured researches published by Mustafa Akgün.
Journal of Earth System Science | 2014
Mustafa Akgün; Tolga Gönenç; Oya Pamukçu; Şenol Özyalın
Loss of life and property that may occur as a result of a possible earthquake can be reduced by earthquake resistant building designs. In order to investigate possible ground motion amplification in earthquake resistant building design, relationship between the ground and engineering bedrock must be ensured. In order to provide this relation, structure, basic characteristics, and thickness of the ground are investigated. In this context, calculating ground transfer function, obtaining horizontal earthquake acceleration changes, calculating Vs values and defining the engineering bedrock are necessary. In this study, Menemen plain, the nothern part of Izmir metropolitan located in active earthquake zone and its immediate vicinity have been examined to define the structure, ground, engineering and bedrock relation. In this context, Menemen plain has been investigated by geophysical methods, which are supported with borehole data (microtremor, MASW – multichannel analysis of surface waves, microgravity measurements, and vertical electrical sounding–VES). Microtremor method was conducted at 377 points in average in the investigation area to define fundamental period and empirical transfer function; after that in order to create basin model and to define the shallow subsurface geometry, microgravity measurements were carried out by using Scintrex CG-5. Also, MASW measurements were carried out in approximately 277 profiles and Schlumberger VES measurements were conducted at approximately 7 points in the investigation area. The existence of a linear relation between H/V peak period values obtained by microtremor measurements and ground thickness in the investigation area is also supported by geothermal drilling logs (depth of 600 m) with microgravity survey. Also, in some parts of the investigation area, it was observed that high S velocity (Vs) values affected H/V peak period values in sections of the ground close to the surface and there was an inversely correlated relation between this ground thickness and peak period values. This event occurring in shallow depths is supported by both VES sections and 2nd order vertical gravity derivative. As a result, depth of the engineering bedrock was obtained between 200 and 700 m and this unit was proposed as Bornova Melange for the investigation area in the scope of the works carried out. Also, it is observed that the area from ground to the engineering bedrock consists of four different layers which were defined by individual S velocities and densities. According to all results, characterictics of the shallow subsurface show that there is a high heterogeneity. Therefore, according to Eurocode8 (EC8 2004) regulations, soil characteristic of the Menemen plain and its vicinity are in the S1–S2 soil class.
Earthquake Engineering and Engineering Vibration | 2017
Eren Pamuk; Özkan Cevdet Özdağ; Şenol Özyalın; Mustafa Akgün
To determine the shear wave velocity structure and predominant period features of Tınaztepe in İzmir, Turkey, where new building sites have been planned, active–passive surface wave methods and single-station microtremor measurements are used, as well as surface acquisition techniques, including the multichannel analysis of surface waves (MASW), refraction microtremor (ReMi), and the spatial autocorrelation method (SPAC), to pinpoint shallow and deep shear wave velocity. For engineering bedrock (Vs > 760 m/s) conditions at a depth of 30 m, an average seismic shear wave velocity in the upper 30 m of soil (AVs30) is not only accepted as an important parameter for defining ground behavior during earthquakes, but a primary parameter in the geotechnical analysis for areas to be classified by Vs30 according to the National Earthquake Hazards Reduction Program (NEHRP). It is also determined that Z1.0, which represents a depth to Vs = 1000 m/s, is used for ground motion prediction and changed from 0 to 54 m. The sediment–engineering bedrock structure for Tınaztepe that was obtained shows engineering bedrock no deeper than 30 m. When compared, the depth of engineering bedrock and dominant period map and geology are generally compatible.
INTERNATIONAL CONFERENCE ON ADVANCES IN NATURAL AND APPLIED SCIENCES: ICANAS 2016 | 2016
Eren Pamuk; Özkan Cevdet Özdağ; Mustafa Akgün
Properties of the soil from the bedrock is necessary to describe accurately and reliably for the reduction of earthquake damage. Because seismic waves change their amplitude and frequency content owing to acoustic impedance difference between soil and bedrock. Firstly, shear wave velocity and depth information of layers on bedrock is needed to detect this changing. Shear wave velocity can be obtained using inversion of Rayleigh wave dispersion curves obtained from surface wave methods (MASW- the Multichannel Analysis of Surface Waves, ReMi-Refraction Microtremor, SPAC-Spatial Autocorrelation). While research depth is limeted in active source study, a passive source methods are utilized for deep depth which is not reached using active source methods. ReMi method is used to determine layer thickness and velocity up to 100 m using seismic refraction measurement systems.The research carried out up to desired depth depending on radius using SPAC which is utilized easily in conditions that district using of sei...
IOSR Journal of Applied Geology and Geophysics | 2017
Eren Pamuk; Özkan Cevdet Özdağ; Aykut Tunçel; Mustafa Akgün
We used surface wave methods which includes single-station microtremor methods,Multichannel Analysis of Surface Waves (MASW), Refraction Microtremor(ReMi) for determining the shear wave velocity structure, which is important input parameter of ground and soil type definition in geotechnical earthquake analysis, and predominant period features of Bornova Plain (İzmir) and its surroundings in İzmir, Turkey. Engineering bedrock (Vs>760 m/s)depths are obtained in north and south parts of thestudy area. When compared, Vs values, predominant periods and geology are generally compatible.
IOP Conference Series: Earth and Environmental Science | 2017
Aykut Tunçel; Özkan Cevdet Özdağ; Eren Pamuk; Mustafa Akgün
Single Station Microtremor method, which is widely used nowadays, is an effective and easy applicable method. In this study, dynamic amplification factor distributions of the study area were obtained using scenario earthquake parameters with single station microtremor data gathered at 112 points. In addition, a surface wave active method, which is known as MASW (Multichannel Analysis of Surface Waves), was applied at 43 profiles to calculate the soil amplification values. Dynamic amplification factor (DAF), soil amplification, the predominant soil period (PSP), geology and topography data of the study area were analysed together. Dynamic amplification factor and soil amplification values were obtained 2 or higher at about sea level parts of the study area which are generally composed of alluvial units. Additionally, in high altitude regions that are composed of volcanic rocks, relatively lower dynamic amplification factor and soil amplification values were obtained. The minimum amplification value in the study area was 1.15, while the maximum amplification value was 3.05 according to the dynamic amplification results and the soil amplification values were between 1.16 and 3.85 in harmony. It is seen that the obtained DAF values and the soil amplification values calculated from the seismic velocities are very similar to each other numerically and regionally. Because of this, it is concluded that the values of the soil amplification obtained by the MASW method and the calculated DAF values in this study are in harmony with each other. Although the depths of research in these two calculation methods are different from each other, the similarity of the results allows us to arrive at the result of how effective the ground layer is on the amplification. It has a great importance to calculate the amplification values and other dynamic parameters by in situ measurements for a planned plot because geological units can vary even at very short distances in heterogeneously distributed areas.
8th Congress of the Balkan Geophysical Society | 2015
E. Özel; Özkan Cevdet Özdağ; Mustafa Akgün; Atilla Uluğ; Eren Pamuk; Y. İpek
Quasi Transfer Spectrums (QTS) and Dynamic soil amplification factor defining which ratio earthquake acceleration will reach the soil surface by changing is one of the most important factors in seismic risk studies. When computing the value of DAF at a point without a strong motion station, peak horizontal acceleration values at the bedrock and soil transfer function are needed. PGA value at the bedrock can be obtained by using either real seismic records or the earthquake scenario. However, the soil transfer function can be computed observationally and theoretically. Observational soil transfer function is defined by microtremor horizontal/vertical spectral ratio. In case of theoretical computation, the density belonging to the soil layers between the bedrock and the soil surface is used together with the change of P-S wave rates with the depth and the damping factor. In this study, the dynamic amplification factor has been computed for 57 points by using observational QTS obtained by microtremor horizontal/ vertical spectral ratio as well as the earthquake scenario. Also, theoretical soil transfer function at 1 point was obtained through spatial autocorrelation method study and determined to be compatible with observational result.
Pure and Applied Geophysics | 2012
Tolga Gönenç; Mustafa Akgün
Journal of Applied Geophysics | 2017
Eren Pamuk; Mustafa Akgün; Özkan Cevdet Özdağ; Tolga Gönenç
Journal of Geophysics and Engineering | 2013
Mustafa Akgün; Tolga Gönenç; Aykut Tunçel; Oya Pamukçu
Arabian Journal of Geosciences | 2015
Özkan Cevdet Özdağ; Tolga Gönenç; Mustafa Akgün