NEAR FIELD SEISMIC SITE RESPONSE ANALYSIS OF ALLUVIAL BASIN: A CASE STUDY FOR THE GÖLYAKA, DÜZCE, TURKEY

2017-10-13
Yousefı Bavıl, Karım
Koçkar, Mustafa Kerem
Akgün, Haluk
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 Gölyaka basin that is located within the Eastern Marmara Region and that uniquely falls within the bifurcated near field section of the North Anatolian Fault System (NAFS). The surface rupture of the 1999 Düzce and 1999 Kocaeli Earthquakes bound this tectonically formed basin respectively, from south to northwest. Considering the concept given above, the local site conditions and dynamic characteristics of sediments have been evaluated in the study area. Then, the basin geometry has been developed to characterize the sediment conditions based on the Vs profilesthat has successfully developed through the surface seismic surveys at 29 sites. To identify the local site effects, the site response analysis (SRA) has been widely used to quantify the local site conditions on propagated ground motions in research and practice. Hence, 1-D site response analyses have been performed considering the nonlinear behavior of the soil deposits using an equivalent linear approach. Then, these results have been correlated with the developed basin model determined by Vs profiles. In general, the site response analyses conducted in the lower Vs prone areas (<180 m/s) demonstrated higher de-amplification levels even in strong motion due to nonlinear behavior in near field (i.e., topographic effect, basin geometry). Similarly, this effect was also unexpectedly observed at some places in the center of the basin for Vs ranges between 180- 360 m/s. Although, the sites near the fault rupture show higher amplification, due to topographic effects some exhibit lower amplification for strong motion. Furthermore, apart from the reliable results, the 1-D site response analyses results could not be accurately verified at some places because of the local site effects that could have generated spatial variations in the near field site depending on the dimensional basin geometry and topographical effects.
Citation Formats
K. Yousefı Bavıl, M. K. Koçkar, and H. Akgün, “NEAR FIELD SEISMIC SITE RESPONSE ANALYSIS OF ALLUVIAL BASIN: A CASE STUDY FOR THE GÖLYAKA, DÜZCE, TURKEY,” presented at the 4. Uluslararası Deprem Mühendisliği ve Sismoloji Konferansı, 11 - 13 Ekim 2017, Eskişehir, Türkiye, 2017, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/81245.