Identifying the occurrence time of an impending major earthquake: a review          下载免费PDF全文

Panayiotis A. Varotsos  Nicholas V. Sarlis  Efthimios S. Skordas 《地震科学（英文版）》2017,30(4):209-218

The procedure through which the occurrence time of an impending major earthquake can be determined is reviewed in the light of the recent advances. This can be achieved by analyzing in natural time the seismicity in the candidate area. To apply this general procedure, we need two important elements: first, to know when we should start the analysis, i.e., set the natural time equal to zero. This is the time at which the system enters the critical stage. Second a reliable estimation of the candidate epicentral area. If geoelectrical measurements are taken and the VAN method (after the initials of the three researchers Varotsos, Alexopoulos and Nomicos) is applied, both these elements become available upon the recording of a precursory Seismic Electric Signals (SES) activity, because its initiation marks the time when the system enters the critical stage, and in addition the SES data enable the determination of the epicentral area of the impending mainshock. On the other hand, if geoelectrical data are lacking, we make use of the following two recent findings by means of natural time analysis: First, the fluctuations of the order parameter of seismicity in a large area exhibit a minimum a few months before a major earthquake almost simultaneously with the initiation of an SES activity. Second, a spatiotemporal study of this minimum unveils an estimate of the epicentral area of the impending major earthquake. Two examples are given that refer to the strongest earthquakes that occurred in Greece and Japan during the last 3 decades, i.e., the M _W6.9 earthquake in southwestern Greece on 14 February 2008 and the M _W9.0 Tohoku earthquake in Japan on 11 March 2011.  相似文献   

The importance of wind forcing in fjord wave modelling     

Christakos  Konstantinos  Furevik  Birgitte R.  Aarnes  Ole Johan  Breivik  Øyvind  Tuomi  Laura  Byrkjedal  Øyvind 《Ocean Dynamics》2020,70(1):57-75

Ocean Dynamics - Accurate predictions of surface ocean waves in coastal areas are important for a number of marine activities. In complex coastlines with islands and fjords, the quality of wind...  相似文献   

Predictive model for site specific simulation of ground motions based on earthquake scenarios          下载免费PDF全文

Christos Vlachos  Konstantinos G. Papakonstantinou  George Deodatis 《地震工程与结构动力学》2018,47(1):195-218

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Finite element analysis of the seismic response of ancient columns     

Konstantinos Papadopoulos  Elizabeth Vintzileou  Ioannis N. Psycharis 《地震工程与结构动力学》2019,48(13):1432-1450

This paper presents a numerical study of the response to earthquake actions of eight ancient Greek multidrum columns, which were chosen as representative of a broad spectrum of the ancient columns preserved to date. The study was conducted using the FE software Abaqus, in three steps. At first, the software efficiency to predict the rocking response of dry-stone structures was verified. Afterwards, various numerical models of one typical ancient multidrum column were seismically excited. Records of four real earthquakes differing in frequency content were used for the excitation of the models. Each column model was different from the others at least in one geometric or modeling parameter. Although the examined parameters affected the numerical results, their variation did not alter significantly the overall behavior of the column. In the last step of the study, numerical models of eight columns were seismically excited using four seismic records. In these analyses, among the simulation approaches tested in the second step, the simpler one was adopted. On the basis of the numerical results, conclusions were drawn regarding the seismic resistance of the columns and its correlation with the dynamic characteristics of the columns (size, slenderness, and frequency parameter) and with the basic intensity measures and frequency content indicator of the seismic motions (PHA, PHV, PHD, and T_g). Thus, criteria of seismic collapse for the multidrum columns are proposed, which can be used for the approximate assessment of the seismic vulnerability of free-standing ancient columns, provided that the columns are in good preservation state.  相似文献   

Direct estimation of seismic response in reduced-degree-of-freedom isolation and energy dissipation systems     

Konstantinos I. Gkatzogias  Andreas J. Kappos 《地震工程与结构动力学》2019,48(10):1112-1133

A methodology for the development of design tools for direct estimation of peak inelastic response in reduced-degree-of-freedom (RDOF) isolation and energy dissipation systems is presented. The suggested procedure is an extension of an earlier method addressing purely hysteretic isolation systems. Herein, the dynamic equation of motion is first normalised to reduce the number of design parameters that significantly affect the response. The sensitivity of normalised response quantities to the amplitude of the ground motion is then investigated through extensive parametric nonlinear dynamic analyses of isolated single-degree-of-freedom (SDOF) systems with linear viscous damping using code-based target spectra. Regression analysis is subsequently employed to develop generalised design equations (GDEs) suitable for design. Further investigations are made to address nonlinear viscous damping and the effect of the transverse component of seismic action in two-degree-of freedom (2DOF) systems under bidirectional excitation, making the procedure applicable to common bridge isolation schemes. GDEs constitute an alternative to equivalent linearisation approaches commonly adopted by codes, informing the selection among alternative isolation and energy dissipations schemes without requiring iterative analysis. The approach is incorporated in the Deformation-Based Design methodology for seismically isolated bridges in a forthcoming paper.  相似文献