Predicting soil behavior under dynamic load due to earthquakes is pivotal for engineering structures and human life. Due to various limitations, such as insufficient computers and difficulties in generating models, the third-dimension effect is generally neglected in many studies. Conversely, the third-dimension effect in regions with high topographic differences, deep basins, three-dimensional heterogeneous and anisotropic environments, and alluvium is at a level that cannot be neglected. This study created a three-dimensional model of the northwest of Turkey for the first time by including surface topography. Soil properties were added to this model, and dynamic analysis was performed. This new model aims to increase the accuracy of ground motion predictions in Northwest Turkey. The accuracy of this model was analyzed using real earthquake data recorded in the study area. In addition, a new software (SiteEffect3D) with various features has been developed to create a three-dimensional mesh with topography using digital elevation model data and to perform dynamic analysis more effectively. This software has been tested comparatively with “Plaxis 3D” software using synthetic terrain models. The importance of this study is that in addition to its contributions to site response analysis and seismic hazard assessment, new software has been developed that can be used in similar studies. The findings will provide valuable information for seismic design and construction practices and facilitate the development of more effective strategies to reduce the potential damage from earthquakes in the region.

Soil amplification is known as the increase in amplitudes of seismic waves as they pass through the soil layers.It depends on many factors such as seismic bedrock depth and slope, the thickness of its layers, physical and lithological properties, discontinuities, and topography.In this study, the effect of surface topography on local soil amplification was investigated.A software called SiteEffect3D has been developed to examine soil behavior with the threedimensional finite element method.With the software, the effect of surface topography on local soil amplification was investigated using various three-dimensional models.These models were exposed to two synthetic acceleration records as well as the 17 August 1999 Izmit earthquake (Mw.7.4) acceleration record.Peak ground acceleration values at the nodal points of the surface topography elements were obtained and plotted as a result of the dynamic analysis.Dynamic analysis results show that peak ground acceleration values change significantly when surface topography is used.Peak ground acceleration values are high on hills with few flat areas, and the slope of the hill also affects the result.There are also remarkable changes in the Peak Ground Acceleration results on the hills located in the regions where the flat areas are wider.However, the effect of the slope is relatively less on the hills in the wide plains.

Günümüzde verilerin toplanması ve analiz edilmesindeki kolaylıkları nedeniyle doğal kaynaklı sismik yöntemler mikro bölgeleme çalışmalarında tercih edilmektedir. Ankara İlinin batısında yer alan, yerleşimin hızlı arttığı Ankara Çayı yatağını oluşturan Kuvaterner çökel birimin kalınlığını, kayma dalgası hızının derinlikle değişimini ve rezonans frekansını belirlemek amacıyla 18 farklı noktada Genişletilmiş Uzamsal Öz İlişki (SPAC) yöntemi ile veriler toplanmış ve değerlendirilmiştir. Elde edilen sonuçlar araştırmaya konu olan Kuvaterner yaşlı birimin beklenenden daha kalın olduğunu ve değişken geometri sunduğunu ortaya koymuştur. Bulgular uluslararası yapı kodlarında ve yönetmeliklerinde yer alan ve jeoteknik mühendisliğinde yaygın olarak kullanılan Vs30 değerinin bu tür bölgeler için yeterli olamayacağına işaret etmektedir.

Joint inversion of data sets collected by using several geophysical exploration methods has gained importance and associated algorithms have been developed. To explore the deep subsurface structures, Magnetotelluric and local earthquake tomography algorithms are generally used individually. Due to the usage of natural resources in both methods, it is not possible to increase data quality and resolution of model parameters. For this reason, the solution of the deep structures with the individual usage of the methods cannot be fully attained. In this paper, we firstly focused on the effects of both Magnetotelluric and local earthquake data sets on the solution of deep structures and discussed the results on the basis of the resolving power of the methods. The presence of deep-focus seismic sources increase the resolution of deep structures. Moreover, conductivity distribution of relatively shallow structures can be solved with high resolution by using MT algorithm. Therefore, we developed a new joint inversion algorithm based on the cross gradient function in order to jointly invert Magnetotelluric and local earthquake data sets. In the study, we added a new regularization parameter into the second term of the parameter correction vector of Gallardo and Meju (2003). The new regularization parameter is enhancing the stability of the algorithm and controls the contribution of the cross gradient term in the solution. The results show that even in cases where resistivity and velocity boundaries are different, both methods influence each other positively. In addition, the region of common structural boundaries of the models are clearly mapped compared with original models. Furthermore, deep structures are identified satisfactorily even with using the minimum number of seismic sources. In this paper, in order to understand the future studies, we discussed joint inversion of Magnetotelluric and local earthquake data sets only in two-dimensional space. In the light of these results and by means of the acceleration on the three-dimensional modelling and inversion algorithms, it is thought that it may be easier to identify underground structures with high resolution.

Summary The soil characteristics in the area located south of Chania city in Crete (Greece) is investigated to get insight about the dynamic behaviour of the ground during an earthquake vibration and to form a basis for further studies. To implement this scope, multi-channel analysis of surface wave method at 4 sites in the summer of 2015 and ambient noise data at 113 sites in the summer of 2016 were collected. The analysis results of the geophysical data show relatively high seismic amplifications and relatively weak resistance to an earthquake vibration in the central and the coastal sites.

ABSTRACTIt is widely known that seismic shear‐wave velocity is one of the most important parameters in site characterization studies. In some instances, it is necessary to determine shear‐wave velocity indirectly from common in situ tests, such as the cone penetration test. There are numerous earlier studies showing this possibility. In this study, the relation between shear‐wave velocity and subsoil geotechnical properties, e.g., cone‐tip resistance and sleeve friction from cone penetration test is reinvestigated in a study area located in Eskisehir, Turkey. New polynomial models are proposed for the correlation. A total of 437 samples extracted from 37 sites made of clay, sand, sand‐clay mixture, and miscellaneous soil types have been used. We compare our results involving polynomial fitting with earlier results of statistical correlation using power‐law or logarithmic relations between shear‐wave velocity and cone‐tip resistance or sleeve friction. The predicted values using our model are checked against the measured ones to evaluate the performance of the polynomial model. The results suggest that the newly proposed approach provides a means for recognizing more efficiently the patterns in the data and reliably predicting the shear‐wave velocity. Additionally, the sensitivity analysis reveals the influence of parameters and the contribution of each coefficient in the polynomial model. Cone penetration test cone‐tip resistance relates more strongly than sleeve friction to shear‐wave velocity. The intercept term in the polynomial is of primary importance in such correlation, for all soil types.

The specification of the near surface ground conditions is highly important for the design of civil constructions. These conditions determine primarily the ability of the foundation formations to bear loads, the stress – strain relations and the corresponding settlements, as well as the soil amplification and corresponding peak ground motion in case of dynamic loading. The static and dynamic geotechnical parameters as well as the ground-type/soil-category can be determined by combining geotechnical and geophysical methods, such as engineering geological surface mapping, geotechnical drilling, in situ and laboratory testing and geophysical investigations. The above mentioned methods were combined, through the Thalis ″Geo-Characterization″ project, for the site characterization in selected sites of the Hellenic Accelerometric Network (HAN) in the area of Crete Island. The combination of the geotechnical and geophysical methods in thirteen (13) sites provided sufficient information about their limitations, setting up the minimum tests requirements in relation to the type of the geological formations. The reduced accuracy of the surface mapping in urban sites, the uncertainties introduced by the geophysical survey in sites with complex geology and the 1D data provided by the geotechnical drills are some of the causes affecting the right order and the quantity of the necessary investigation methods. Through this study the gradual improvement on the accuracy of site characterization data is going to be presented by providing characteristic examples from a total number of thirteen sites. Selected examples present sufficiently the ability, the limitations and the right order of the investigation methods.

Edge enhancement and detection techniques are fundamental operations in magnetic data interpretation. Many techniques for edge enhancement have been developed, some based on profile data and others designed for grid-based data sets. Methods that are traditionally applied to magnetic data, such as total horizontal derivative (THD) and analytic signal (AS), require the computation of integer-order horizontal and vertical derivatives of the magnetic data. However, if the data set contains features with a large variation in amplitude, then the features with small amplitudes may be difficult to outline. In addition, because most edge enhancement and detection filters are derivative-based filters, they also amplify high-frequency noise content in the data. As a result, the accuracy of derivative-based filters is restricted to data of high quality. We suggested the modification of the THD and AS filters by combining the amplitude spectra of fractional-order-derivative filters with ad hoc phase spectra, particularly designed for edge detection in magnetic data. We revealed the capability of the proposed algorithm on synthetic magnetic data and on aeromagnetic data from Turkey. Compared with the traditional use of THD and AS (with integer-order derivatives), we developed the method based on fractional-order derivatives that produced more effective results in terms of suppressing noise and delineating the edges of deep sources.

Shear wave velocity ( V S ) is a basic engineering property implemented in evaluating the soil shear modulus. In many instances it may be preferable to determine V S indirectly by common in-situ tests, such as the Standard Penetration Test (SPT). In this paper, the relationship between V S and geotechnical soil parameters such as standard penetration test blow counts ( N 160 ), effective stress and fines content, as well as overburden stress ratio (σ vo /σ ′ vo ), is investigated. A new mode based on support vector machine (SVM) approach is proposed to correlate geotechnical parameters and V S , predicated on a total of 620 data sets, including field investigation records for the Kocaeli (Turkey, 1999) and Chi-Chi (Taiwan, 1999) earthquakes. This study addresses the question of whether Support Vector Machine (SVM) approach should be used to estimate V S based on the specified geotechnical variables, and assessing the influence of each variable on V S . Results revealed that SVM, in comparison to previous statistical relations, provides an effective means of efficiently recognizing the patterns in data and accurately predicting the V S .

Summary Recent advances in Seismic Codes increased the necessity in Engineering Geophysics to use surface wave analysis as a tool. The shear wave velocity profile had to be resolved to calculate the site amplification in case of an earthquake event, necessary also for seismic hazard studies. In our approach we present the results from Surface Wave data acquired in different site in Crete Island (Greece) at strong motion sites. Passive and Active data at linear and circular geometries have been analyzed and the corresponding processing and inversion results are compared. Although one would comment that there are discrepancies on Dispersion Curve results the resulted ground profiles up to a shallow depth show considerable agreement. However, this is site dependent and in order to increase the accuracy and reliability of results one should be careful with the assignment of different modes in surface wave analysis and also combine the results provided.

ÖZHistogram eşitleme, görüntü histogramını kullanarak görüntü karşıtlığının ayarlanması için yaygın olarak kullanılan bir yöntemdir.Yöntem, bir görüntüde düşük karşıtlık değerleriyle betimlenen bölümlerin karşıtlık değerlerini arttırır.Bu düzeltme sayesinde görüntüdeki parlaklık değerleri görüntü histogramı üzerinde daha iyi bir dağılım sergiler.Düşük yerel karşıtlıktaki bölümlerin bir kazanç işlemi sonrası yüksek zıtlık değerlerine taşınması göze çarpmayan bölgelerin görünürlüğünün artmasına ve böylelikle görüntünün daha iyi yorumlanmasına olanak sağlar

To estimate the seismic response according to Eurocode (EC8) and almost all other national codes, site conditions have to be properly characterized so that soil amplification and the corresponding peak ground motion can be calculated.In this work, different geophysical and geotechnical methods are combined in order to define the detailed ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in Crete. For this purpose, the geological information of the sites and shear wave velocity, calculated from surface wave measurements, is used. Additionally, ground acceleration data recorded through HAN have been utilized from intermediate depth earthquakes in the broader area of South Aegean Sea.Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for the selected sites. The resulting information is compared to the values defined in the corresponding EC8 spectrum for the seismic zone that includes the island of Crete.The comparison shows that accurate definition of ground type through geological, geotechnical and geophysical investigations is important. However, our current comparison focuses on the distribution of values rather than the absolute values of EC8-prescribed spectra, and the results should be considered in this context.

Karşılıklı kuyu sismik kırılma verilerinin iki-boyutlu ters çözümünü yapan yeni bir algoritma geliştirilmiştir. Geliştirilen ters çözüm algoritmasının düz çözüm bölümünde Hızlı İlerleme Yönteminde köşegen elemanları da kullanan bir yöntem kullanılmıştır. Bu kullanım sayesinde köşegen yönündeki hesaplama hataları minimize edilmiştir. Geliştirilen ters çözüm algoritması yapay veriler kullanılarak test edilmiş ve ilksel sonuçları sunulmuştur. Anahtar Kelimeler: Karşılıklı Kuyu, Sismik, Hızlı İlerleme Yöntemi, Ters Çözüm

For the seismic action estimation according to Eurocode (EC8) one has to characterize site conditions and suitably estimate soil amplification and corresponding peak ground motion for the site. For this reason, as specified, one has to define a design spectrum through the ground-type/soil-category (S), and the peak ground acceleration (PGA) of the reference return period (TNCR) for the corresponding seismic zone and for structural technical requirements chosen by the designer. Ground type is defined through geophysical/geotechnical parameters, i.e. (a) the average shear wave velocity up to 30 meters depth, (b) the Standard Penetration Test blow-count, and (c) the undrained shear strength of soil.Through the "GEO-CHARACTERIZATION" THALIS-PROJECT we combine different geophysical and geotechnical methods in order to more accurately define the ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in the area of Crete Island. More specifically in the present efforts, geological information shear wave velocity and attenuation model calculated from seismic surface geophysical measurements is used. Additionally we utilize the ground acceleration recorded through HAN from intermediate depth earthquakes in the broader area of South Aegean Sea.Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for selected sites. The resulting information are compared with the values defined for the corresponding EC8 spectrum for the seismic zone comprising the island of Crete.As a final outcome of this work we intend to propose regional normalized elastic spectra for seismic design of structures and urban development planning and compare them with Eurocode.

The geo-characterization of site conditions is crucial for the estimation of regional elastic spectra. The work to be done in the framework of the “GEO-CHARACTERIZATION” THALIS-project, will combine geotechnical and geophysical methods and evaluate them to estimate critical geotechnical parameters. Although geotechnical tests in lab may provide more accurate estimates of geotechnical parameters, they require costly and time consuming drilling procedures. On the other hand geophysical methods are useful in providing estimates in situ of subsurface physical properties, which are not directly related to geotechnical parameters. Within “GEO-CHARACTERIZATION” THALIS-project a pilot survey for geotechnical characterization at selected sites of Hellenic Accelerometric Network in Crete will be conducted by employing geotechnical, geological and geophysical techniques. Subsequently, by correlating “geo-data” collected within this project, relations of certain mechanical parameters obtained in laboratory or/and in situ with geophysical parameters for typical geologic formations and soils will be established. The “GEO-CHARACTERIZATION” project, will focus on the influence of dynamic loads on geotechnical phenomena related to the static stress field variation, the estimation of site effects due to seismic motion and the proposal of regional elastic spectra for seismic provisions as well as their comparison with the corresponding elastic design spectra of Eurocode 8 (EC8).

The ancient theatres comprise a unique group of excellent architecture retaining their magnificence through the centuries. Recently there is an increased interest in activities associated with their restoration and exhibition. During the preliminary stage of planning restoration activities, geophysical prospection methods can provide the only non-destructive tool to identify the preservation level of such monuments. The importance of the implementation of different geophysical techniques is signified through the representation of two case studies from Greece. A suite of integrated geophysical methodologies composed of Ground Penetrating Radar (GPR), three-dimensional (3-D) Electrical Resistivity Tomography (ERT), electrical resistance, gradiometer mapping techniques and seismic methods (refraction tomography and Multichannel Analysis of Surface Wave-MASW) techniques were evaluated in rediscovering the small theatre and the amphitheatre of Ierapetra (SE Crete). The geophysical investigations followed the descriptions, maps and plans given by past travellers of Crete who witnessed and recorded the existence of these monuments centuries ago. Although the accuracy of such evidence has been frequently questioned in the past, geophysical approaches can be used as a tool for verifying the older testimonies. Despite the difficulties in such an effort these works’ results revealed the importance of geophysical methods in the preservation of these monuments.

GPS studies in Turkey date back to the early 1990s, but were mostly focused on the seismically active North Anatolian Fault System (NAFS), or on the more populated Western Anatolia. Relatively few studies were made of the seismically less-active East Anatolian Fault System (EAFS), although it has the potential to produce large earthquakes. In this study, we present the results of a combination of geodetic and seismological data around the Karliova Triple junction (KTJ), which lies at the intersection of the North- and East Anatolian Fault Systems. In particular, the geodetic slip rates obtained through block modeling of GPS velocities were compared with b-values to assess seismicity in the region. Yedisu segment, one of the best-known seismic gaps in Turkey, was specifically analyzed. The relatively low b-values across Yedisu segment verify the accumulation of seismic energy in this segment, and the GPS-derived geodetic slip rates suggest that it has the potential to produce an earthquake of Mw 7.5 across an 80-km rupture zone.Additionally, analysis of earthquake data reveals that the study area has a ductile or rigid-ductile behavior with respect to its surroundings, characterized by varying b-values. Although, seismic events of moderate- to high magnitudes are confined along the major fault zones, there are also low-seismicity zones along the eastern part of the Bitlis Suture Zone and around Yedisu. Since the high seismicity areas within the region may not accumulate sufficient stress for a large earthquake to occur, it is considered that the deformation in such areas occurs in a ductile manner. On the other hand, the areas characterized by low b-values may have the capacity of stress accumulation, which could lead to brittle deformation. (C) 2012 Elsevier Ltd. All rights reserved.

An open-source software including an easy-to-use graphical user interface (GUI) has been developed for processing, modeling and mapping of gravity and magnetic data. The program, called Potensoft, is a set of functions written in MATLAB. The most common application of Potensoft is spatial and frequency domain filtering of gravity and magnetic data. The GUI helps the user easily change all the required parameters. One of the major advantages of the program is to display the input and processed maps in a preview window, thereby allowing the user to track the results during the ongoing process. Source codes can be modified depending on the users' goals. This paper discusses the main features of the program and its capabilities are demonstrated by means of illustrative examples. The main objective is to introduce and ensure usage of the developed package for academic, teaching and professional purposes.