Zeminlerin dinamik özelliklerinin ve zemin büyütme faktörlerinin alternatif yöntemlerle belirlenmesi.

Earthquakes are among the most destructive natural disasters affecting urban populations. Structural damage caused by the earthquakes varies depending not only on the seismic source and propagation properties but also on the soil properties. The amplitude and frequency content of seismic shear waves reaching the earth’s surface is dependent on local soil conditions. It is well known that the soft sediments on top of hard bedrock can greatly amplify the ground motion and cause severe structural damage. When the fundamental period of the soil is close to the fundamental period of a structure, structural damage increases significantly. Estimation of the fundamental periods, amplification factors and types of soils is critical in terms of reduction of loss and casualties. For the reasons stated, estimation of dynamic behavior of soils has become one of the major topics of earthquake engineering. Studies for determining dynamic properties of soils depend fundamentally on the estimation of the S-wave velocity profiles, amplification factors and ground response. In this study first, the Multi-Mode Spatial Autocorrelation (MMSPAC) method is used to estimate the S-wave velocity profiles at the sites of interest. This method is different than the other ones in the sense that it works for the higher modes as well as the fundamental mode. In the second part, Horizontal to Vertical Spectral Ratio (HVSR) method will be used on both microtremor and ground motion data. Finally, the amplification factors from alternative methods are compared with each other. Consistent results are obtained in terms of both fundamental frequencies and amplification factors.M.S. - Master of Scienc

Evaluation of Site Response with Alternative Methods A Case Study for Engineering Implications

n this paper, efficiency of alternative geophysical techniques for site response is evaluated in two sedimentary basins on the North Anatolian Fault Zone. For this purpose, fundamental frequencies of soils and corresponding amplitudes obtained from empirical horizontal-to-vertical spectral ratio curves from microtremors, weak motions and strong motions are compared with results from one-dimensional theoretical transfer functions. Theoretical transfer functions are computed using S-wave velocity profiles derived from array observations of the microtremor wavefield. Our results are consistent with studies from other regions in that the fundamental frequencies from microtremors, weak motions and theoretical transfer functions are mostly in agreement with each other although some discrepancies are observed. Even though important information about fundamental resonance frequency can be derived from horizontal-to-vertical spectral ratios, observed amplitudes do not yield consistent results with the theoretical amplification factors. Thus, the use of horizontal-to-vertical spectral ratio amplitudes is not recommended for estimation of amplification factors. Based on our observations, complementary use of alternative methods for site response is recommended. © 2017, Springer International Publishing AG

A Regional High-frequency Attenuation (Kappa) Model for Northwestern Turkey

The high-frequency attenuation of spectral amplitudes of S-waves is modeled as an exponential decay in terms of Kappa factor (Anderson and Hough, 1984). It is thus an important parameter of soils identifying the high-frequency attenuation behavior of ground motion as well as one of the key parameters for stochastic strong ground motion simulation method. In particular, for regions with sparse seismic networks, it is crucial to use simulated ground motions which require well-defined regional seismic parameters. Several stochastic simulations have been made for recent earthquakes occurred in Turkey; however there is not yet a systematic investigation of the Kappa parameter from the recently recorded Turkish ground motions. In this study, we examine a strong ground motion dataset from Northwestern Turkey with varying source properties, site classes and epicentral distances. We manually define Kappa from the S-wave portion of each record. We use both traditional regression techniques and data mining approaches to describe the (potential) relationships between Kappa values and independent variables such as the site class, distance from the source or magnitude of the event. Unlike the classical methods, data mining techniques provide a deeper insight to the problem through data analytics, in which a better understanding of existing patterns of data results in higher prediction performances. We then compare the outcomes of data mining techniques with those of traditional methods to better highlight the important characteristics of the ground motion dataset. We express the initial findings of a regional Kappa model for Northwestern Turkey with focus on magnitude, site class and distance dependencies. The Long Beach Seismic Experiment: A Novel High-Density Array to Examine Seismic Scatterin

High-Frequency Attenuation (Kappa, K) Estimations From The Recently-Compiled Turkey Strong Ground Motion Database For Western Turkey

Modeling of near-surface attenuation has significance in a wide range of seismological applications such as site characterization, sitespecific hazard assessment for critical facilities and ground motion predictions. Kappa (k) factor is often used to represent the rate of the attenuation in spectral amplitudes at high frequencies (f > 10 Hz) and it is also one of the essential parameters for stochastic strong ground motion simulation method. Although the origin and physical components of k is still under debate, it is considered to be a combination of site and path effects. Moreover, a source component could also contribute to variability in kappa estimates. Zero-distance kappa value (k0) is computed as an indicator of the spectral attenuation due to top soil layers, eliminating the path effects. In this study, we used the recentlycomplied strong ground motion database of Turkey which consists of records from mostly small and moderate-size earthquakes with a smaller number of records from large events. k factors are manually computed from the S-wave portion of both horizontal and vertical components for each record as we observed variations in k values for different components. Next, magnitude and epicentral distance dependence of the k values are studied. We use multivariate linear regression analyses to describe the relationships between the studied kappa dataset and selected independent variables such as the site class, distance and magnitude. Kappa estimates reveal that there is a significant scattering at the majority of the investigated sites. The scattering of these initial kappa estimates could be attributed to the influence of the sourceand wave propagation effects associated with the complex tectonic structure of the region