Evaluation of the site effects of the Ankara basin, Turkey

2012-08-01
Kockar, M. K.
Akgün, Haluk
Recent major earthquakes have explicitly demonstrated that near-surface local site conditions that can generate significant amplifications and spatial variations of earthquake ground motion play a major role in the level of ground shaking and in gathering information on soft soil response. It is therefore highly desirable to develop methods to identify and characterize regions that are prone to this type of site amplification. To determine the subsurface sediment characteristics over a wide area, measurement and analyses of microtremor have been widely employed. Considered to be a relatively easy and economically attractive method for collecting relevant information especially in urbanized areas, microtremor involves utilization of ambient seismic noise to evaluate the local site effects reliably which is one of the vital aspects of seismic hazard assessment. This paper aims to investigate the site response of the sediment characteristics in Ankara, the capital of Turkey through conducting short-period noise recordings of microtremor measurements. A total of 352 microtremor measurements have been performed in the project site within the Plio-Pleistocene fluvial and Quaternary alluvial and terrace sediments in the western part of the Ankara basin. The spectral ratio between the horizontal and vertical components (H/V) of the microtremor measurements at the ground surface has been used to estimate the fundamental periods and amplification factors of the site. The microtremor study was also correlated and complemented by in-situ seismic measurements of dynamic properties, geologic information, and some geotechnical boring information in the project area for evaluating site conditions in an account to estimate site effects. The results of this study identified three main factors that influence site response, namely, the age of the local geological formation, the depth of the soil thickness and soil characteristics in the younger sediments, and non-uniform subsurface configurations. In particular, the H/V results showed that the variation of the fundamental period map agreed well with the maximum value of the amplification as well as with the local site conditions of seismic sediment characteristics that provided reliable estimates of site response of soft soil deposits. Finally, these results were used in zonation studies for reliably determining the local site characteristics.
JOURNAL OF APPLIED GEOPHYSICS

Suggestions

NEAR FIELD SEISMIC SITE RESPONSE ANALYSIS OF ALLUVIAL BASIN: A CASE STUDY FOR THE GÖLYAKA, DÜZCE, TURKEY
Yousefı Bavıl, Karım; Koçkar, Mustafa Kerem; Akgün, Haluk (null; 2017-10-13)
Seismic events in the last few decades have demonstrated that local site conditions particular near earthquake prone areas that can generate significant amplifications and spatial variations of earthquake ground motion play a major role in the level of ground shaking. Hence, the amplification of ground motion due to local site effects (i.e., topographical conditions, ground motion resonance and basin geometry, etc.) plays an important role in increasing seismic damage. The study area is located in the Gölya...
Evaluation of Site Characterizations and Site Effects of the Ankara Basin Turkey
Koçkar, Mustafa Kerem; Akgün, Haluk (2007-06-28)
The purpose of this study is to assess the in-situ site characteristics and to perform seismic hazard studies of the Upper Pliocene to Pleistocene fluvial and Quaternary alluvial and terrace deposits located towards the west of Ankara. Based on a general engineering geological, geotechnical and seismic characterization of the site, site classification systems were assigned for seismic hazard evaluations. Then, short-period noise recordings of the microtremor measurements at the ground surface have been used...
Evaluation of site effects based on the 1999 Kocaeli and Düzce earthquake events and seismic microzonation of Gölyaka, Düzce, Turkey
YOUSEFI BAVIL, KARIM; Akgün, Haluk; Koçkar, Mustafa Kerem; Department of Geological Engineering (2022-2)
The high seismicity study area situated in a near-fault region in Gölyaka, Düzce, makes the determination of the bedrock geometry more complex, and hence, it makes this area very challenging in terms of a site response study that would aid a seismic hazard assessment. This study developed a basin model to evaluate the site effects in the tectonically controlled and formed Plio-Quaternary fluvial sediments of the Gölyaka region that uniquely falls within the bifurcated near-field fault section of the North A...
Comparative study of base isolated systems
Türkmen, Fatih; Akyüz, Uğurhan; Department of Civil Engineering (2002)
This thesis is mainly concerned with providing brief knowledge about the effects of earthquakes on buildings and their response to earthquake forces. Principles of advanced passive earthquake resistant design techniques are also presented. Next, the use of the most common passive earthquake resistant design technique; i.e., base isolation is described, with its historical background, main principles and usage in the world. In order to evaluate the effectiveness of base isolation, and the performance of base...
Predicting intensity and damage distribution during the 1995 Dinar, Turkey, earthquake with generated strong motion accelerograms
Sucuoğlu, Haluk; Zeng, YH (2003-06-01)
A source model for the 1995 Dinar earthquake that is capable of reproducing reasonably well the statistical characteristics of observed strong motion records is used to generate synthetic ground-motion accelerograms at 29 different sites along five east-west cross sections in the city. Each section crosses a distribution of topographical, geotechnical, and damage characteristics. All synthetic stations are located within a circle of approximately 4-km diameter, and a segment of the ruptured fault extends in...
Citation Formats
M. K. Kockar and H. Akgün, “Evaluation of the site effects of the Ankara basin, Turkey,” JOURNAL OF APPLIED GEOPHYSICS, pp. 120–134, 2012, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/35279.