Eren Pamuk

Soil characterization of Tınaztepe region (İzmir/Turkey) using surface wave methods and nakamura (HVSR) technique

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.

Analysis shear wave velocity structure obtained from surface wave methods in Bornova, Izmir

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...

Investigation of Shear Wave Velocity and Predominant Period Properties of Bornova Plain (IZMIR) and Its Surroundings

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.

Comparison of the Soil Dynamic Amplification Factor and Soil Amplification by Using Microtremor and MASW Methods Respectively

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.

Relationship Between Quasi Transfer Spectrums and Dynamic Amplification Factor

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.

Application of Different Algorithms to an Inversion of Rayleigh Wave Dispersion Curve

Inversion of surface wave dispersion curve is a important process for Vs analysis. We tried three algorithms which are the genetic algorithm (GA), least squared method (LSM) and neighbourhood algorithm (NA). These algorithms were utilized for inversion of dispersion curve obtained from surface wave method. Both synthetic and measured data sets were considered. Calculated dispersion curves in the synthetic test study by using GA, NA and LSM algorithms fitted observed dispersion curve with acceptable misfits. Surface wave methods were utilized on measured data in order to determine elastic ground characteristic of Dokuz Eylul University campus in Izmir (Turkey). The variation of shear wave velocity (Vs) with depth could be determined by using dispersive behaviour of Rayleigh waves in surface wave analysis methods. The shear wave velocity cross-sections were obtained by inversion of dispersion curves. The estimated parameters which were obtained from all algorithms were compared with each other and calculated dispersion curves in the field test study by GA, NA and LSM algorithms fitted observed dispersion curve with acceptable misfits as synthetic study. Results of calculated dispersion curves which were obtained from all algorithms are compared with observed dispersion curve. Shear wave velocity cross sections were prepared for all algorithms.