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41.
The western part of Anatolia is one of the most seismically and tectonically active continental regions in the world, and
much of it has been undergoing NS-directed extensional deformation since the Early Miocene. In this study, we determine 3-D
tomographic images of the crust under the southwestern part of the North Anatolian Fault Zone by inverting a large number
of arrival time data of P and S waves. From the obtained P- and S-wave velocity models, we estimated the Poisson’s ratio structures for a more reliable interpretation of the obtained anomalies.
Our tomographic results confirmed the major tectonic features detected by previous studies and revealed new structural heterogeneities
related to the active seismotectonics of the studied area. High P-wave velocity anomalies are recognized near the surface, while at deeper crustal layers, low P-wave velocities are widely distributed. The crustal S-wave velocity and Poisson’s ratio exhibit more structural heterogeneities compared to the P-wave velocity structure. Microearthquake activity is intense along highly heterogeneous zones in the southwestern part, which
is characterized by low to high P-wave velocity, low S-wave velocity, and high Poisson’s ratio anomalies. Large earthquakes are also concentrated in zones dominated by low velocities
and low to high Poisson’s ratios. Results of the checkerboard and synthetic tests indicate that the imaged anomalies are reliable
features down to a depth of 25 km. Moreover, they are consistent with many geological and geophysical results obtained by
other researchers along the southwestern part of the North Anatolian Fault Zone.
An erratum to this article can be found at 相似文献
42.
A numerical investigation was undertaken to evaluate the response of dual structural systems that consisting of steel plate shear walls and moment‐resisting frames. The primary objective of the study was to investigate the influence of elastic base shear distribution between the wall and the frame on the global system response. A total of 10 walls and 30 wall–frame systems, ranging from 3 to 15 stories, were selected for numerical assessment. These systems represent cases in which the elastic base shear resisted by the frame has a share of 10, 25, or 50% of the total base shear resisted by the dual system. The numerical study consisted of 1600 time history analyses employing three‐dimensional finite elements. All 40 structures were separately analyzed for elastic and inelastic response by subjecting them to the selected suite of earthquake records. Interstory drifts, top story drift, base shears resisted by the wall, and the frame were collected during each analysis. Based on the analysis results, important response quantities, such as the strength reduction, the overstrength, and the displacement amplification factors, are evaluated herein. Results are presented in terms of displacement measures, such as the interstory drift ratio and the top story drift ratio. Analysis results revealed that the increase in the strength reduction factor with the amount of load share is insignificant. Furthermore, there is an inverse relationship between the ductility reduction and the overtsrength. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
43.
This paper describes a seismic test program performed on 12 steel‐encased buckling‐restrained braces (BRBs). The use of rolled or built‐up buckling‐restraining mechanisms with welded or bolted attachments was examined. In addition, the effects of bolt pretension, core‐to‐encasing attachment details, aspect ratio of core segment and imperfections due to manufacturing on the brace response were investigated. All specimens were subjected to a stepwise incremental quasi‐static testing protocol with a maximum axial strain amplitude of 2%. All specimens except one showed satisfactory performance with stable hysteretic response and sustained cumulative inelastic deformations in excess of 200 times the yield deformation. Based on the experimental results, the compression strength adjustment factor, and the strain hardening adjustment factor for each excursion were quantified. Test results revealed that these two factors are significantly influenced by the parameters investigated in the experimental program. BRB details were also found to influence the buckling and the yielding patterns of the core segment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
44.
Comparison of missing value imputation methods in time series: the case of Turkish meteorological data 总被引:1,自引:0,他引:1
Ceylan Yozgatligil Sipan Aslan Cem Iyigun Inci Batmaz 《Theoretical and Applied Climatology》2013,112(1-2):143-167
This study aims to compare several imputation methods to complete the missing values of spatio–temporal meteorological time series. To this end, six imputation methods are assessed with respect to various criteria including accuracy, robustness, precision, and efficiency for artificially created missing data in monthly total precipitation and mean temperature series obtained from the Turkish State Meteorological Service. Of these methods, simple arithmetic average, normal ratio (NR), and NR weighted with correlations comprise the simple ones, whereas multilayer perceptron type neural network and multiple imputation strategy adopted by Monte Carlo Markov Chain based on expectation–maximization (EM-MCMC) are computationally intensive ones. In addition, we propose a modification on the EM-MCMC method. Besides using a conventional accuracy measure based on squared errors, we also suggest the correlation dimension (CD) technique of nonlinear dynamic time series analysis which takes spatio–temporal dependencies into account for evaluating imputation performances. Depending on the detailed graphical and quantitative analysis, it can be said that although computational methods, particularly EM-MCMC method, are computationally inefficient, they seem favorable for imputation of meteorological time series with respect to different missingness periods considering both measures and both series studied. To conclude, using the EM-MCMC algorithm for imputing missing values before conducting any statistical analyses of meteorological data will definitely decrease the amount of uncertainty and give more robust results. Moreover, the CD measure can be suggested for the performance evaluation of missing data imputation particularly with computational methods since it gives more precise results in meteorological time series. 相似文献