Seventy-two microtremor measurements were conducted in the northern coast ofİzmir Bay. The dataset has been processed using the horizontal-to-vertical spectral ratio. The fundamental period contour map obtained showed that the fundamental period at rock sites of the northern coast ofİzmir Bay was between 0.15 and 0.35 s. However, the fundamental period increased towards the western direction where thick soft sediments exist, the fundamental period varied between 0.5 and 2.0 s. A soil classification map of the area was prepared based on the data estimated from SPT-N values of 25 boreholes. It is seen that major portion of the study area, including the shore line of the northern coast had SPT-N values lower than 15. The fundamental periods obtained by H/V spectral ratio method and the periods derived from shear wave velocity data available in 11 of 25 boreholes were well-correlated. Fundamental period map obtained from H/V spectral ratio method illustrated the characteristics of weak soil conditions and the presence of bedrock level under thick alluvial soils. Finally, microtremor investigations have proved to be an effective tool for assessment of local soil conditions in case of thick soft sediments in the northern coast ofİzmir Bay.

Presented Structural Seismic Isolation Method (SSIM) aims to provide high safety for Highly Reliable Structures (HRS) against strong earthquakes including near-fault and long-period ground motions. The examined structure is converted to Structural Seismic Isolation System (SSIS) by the SSIM method which exhibited inverse pendulum behaviour. For this purpose, structure foot base and foundation contact surfaces have been designed as any curved surfaces (spherical, elliptical, etc.) depending on the earthquake-soil-superstructure parameters and this contact surfaces have been separated by elastomeric (lead core rubber or laminated rubber bearings) seismic isolation devices. It would allow the structure foot base to turn around gyration centre through rubber bearing contact and maintains similar behaviour to the super-structure. SSIS system provides the possibility of keeping the natural-period of the structure in a larger interval, which is greater than the predominant-period of the majority of possible earthquakes (including near-fault pulse) using currently existing conventional elastomeric isolators with up to 4 second period. Thus, the structure can sustain its serviceability after strong and long-period earthquakes. In this study SSIS system’s performance is presented for high-rise building structures, for this aim, the finite element model of the building (Bg) structure with SSIS system (SSIS-Bg) has been prepared and the nonlinear dynamic analysis of the model has been conducted using strong and long-period ground motions. Results indicate that the base and top accelerations, base shear and base moment responses of the SSIS-Bg structure is 23.21 %, 75.47 % and 85.74 % in average lower than the Conventional Application Method of Seismic Base Isolation Devices for Building (CAMSBID-Bg) structures respectively and it is not prone to resonant vibrations under long-period earthquakes related with the excessive deformation in the isolation layers in case of using CAMSBID-Bg structures. It should be noted that in this study with the presented SSIM method and SSIS system, it is aimed to protect only the Highly Reliable Structures(HRS) from the effects of strong and long-period ground motions and these structures (HRS) are classified as follows: 1) Nuclear Containment Structures; 2) High-rise buildings that contain information, operating systems, sensitive instruments, communication systems, routing systems, bank operating systems, databases, management systems and other similar facilities that are linked to the security and economy of a country; 3) High-rise hospitals etc.

The city of Izmir, located at the western end of Turkey, has experienced many strong earthquakes throughout its history. The southern coast of Izmir Bay, one of the most densely populated areas of Izmir, is located on deep alluvial sediments. It is important to determine the effect of local soil conditions on dynamic ground response in the study area, where thick loose water-saturated alluvial sediments exist. A database including geotechnical and geological information on the study area is constructed. Majority of the site is classified as D and E according to NEHRP provisions. Dynamic site response analyses are performed with EERA by utilizing the field and laboratory test results and earthquake time histories of moderate-scale earthquakes such as 1977 Izmir (M L = 5.3), 2003 Urla (M d = 5.6), and 2005 Uzunkuyu-Urla (M L = 5.9), which occurred in and nearby Izmir. In addition, a scenario ground motion generated by the Izmir Fault with a magnitude of 6.5, having an average distance of 10 km to the study area, is also considered. The output data obtained from the dynamic site response analyses are evaluated, and maps displaying variation in dynamic parameters on ground surface are prepared for the southern coast of Izmir Bay, Turkey. Consequently, the dynamic analyses performed with the soil models constituted for the study area verified the damage occurred in a close distance event of 1977 Izmir earthquake. The scenario earthquake resulted in peak ground accelerations more than 0.6g at the eastern and western ends of the study area. However, long distance events resulted in spectral amplifications by up to 5 times. With this study, it is emphasized that local soil conditions should be evaluated individually in the area of interest. Generation of a site-specific design spectrum is recommended for the areas located on deep alluvial sediments.

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The new Structural Seismic Isolation System (SSIS) intends to provide high safety for important structures such as nuclear power plants, offshore oil platforms, and high-rise buildings against near-fault and long-period earthquakes. The presented SSIS structure foot base and foundation contact surfaces have been designed as any curved surfaces (spherical, elliptical, etc.) depending on the earthquake-soil-superstructure parameters, and these contact surfaces have been separated by using elastomeric (lead core rubber or laminated rubber bearings with up to 4-second period) seismic isolation devices. It would allow providing inverse pendulum behavior to the structure. As a result of this behavior, the natural period of the structure will possess greater intervals which are larger than the predominant period of the majority of the possible earthquakes including near-fault zones. Consequently, the structure can maintain its serviceability after the occurrence of strong and long-period earthquakes. This study has investigated the performance of the SSIS for the nuclear containment (SSIS-NC) structure. The finite element model of SISS-NC structure has been developed, and nonlinear dynamic analysis of the model has been conducted under the strong and long-period ground motions. The results have been presented in comparison with the conventional application method of the seismic base isolation devices for nuclear containment (CAMSBID-NC) and fixed base nuclear containment (FB-NC) structures. The base and top accelerations, effective stress, and critical shear stress responses of the SSIS-NC structure are 48.67%, 36.70%, and 32.60% on average lower than those of CAMSBID-NC structure, respectively. The result also confirms that the SSIS-NC structure did not cause resonant vibrations under long-period earthquakes. On the other hand, there is excessive deformation in the isolation layers of CAMSBID-NC structure.