PSHA for Broad-Band Strong Ground-Motion Hazards in the Saronikos Gulf,Greece, from Potential Earthquake with Synthetic Ground Motions

We perform a probabilistic seismic hazard analysis (PSHA) for broad-band strong ground motion within the Saronikos Gulf region, Greece, from potential earthquakes along the 30 km long Aigina fault in the northern part of the Gulf. We perform the PSHA utilizing empirical Green’s functions (EGFs) merged with synthetic Green’s functions (SGFs) along with models of finite rupture in place of standard “attenuation relations.” Our approach considers all significant magnitudes for PSHA and full broadband ground motion simulations. Calculations are source and site specific, and could reduce uncertainties in estimating standard engineering parameters. We use a range of rupture scenarios for all significant magnitude earthquakes along the fault. The hazard calculation is for frequencies 0.0– 15.0 Hz. Recordings of small earthquakes from an onshore/offshore local seismic array were used as EGFs for frequencies of 1.5–15.0 Hz, the finite difference code E3D was utilized to synthesize SGFs for frequencies 0.0–1.5 Hz, and an algorithm for merging the EGFs with SGFs was developed. The full-waveform calculations are important for non-linear dynamic analysis of structures in the coastal zone and potential hazard to long period structures. Results of proposed PSHA identify 2%, 10%, and 50% hazard at the selected sites of Saronikos Gulf.

Finally, we compare our PSHA results to those obtained by standard practice which involves prediction equations (GMPEs) recently developed in the Next Generation Attenuation (NGA) project and empirical predictive attenuation relations proposed for Greece. We believe that differences with the NGA results are due to site- and source-specific information utilized in this study, and incorporation of this information may significantly reduce the uncertainty in seismic hazard calculations.     

A Test of the Applicability of NGA Models to the Strong Ground-Motion Data in the Iranian Plateau

The Next Generation Attenuation (NGA) project has now published several new sets of empirical ground-motion prediction equations (GMPEs) for PGA, PGV, and response spectral ordinates. These models significantly advance the state-of-the-art empirical ground-motion modeling and account for many effects that have not been directly accounted for in the existing Iranian GMPEs. Assuming that the present strong-motion database in Iran is unlikely to drastically change in the near future, the question we ask in this study is: Can the NGA models be applied in Iran? In order to answer this question, the NGA models of Boore and Atkinson [2008] Boore, D. M. and Atkinson, G. M. 2008. Ground-motion prediction equations for the average horizontal 99 component of PGA, PGV, and 5%-damped PSA at spectral periods between 0.01 s and 10.0 s. Earthquake Spectra, Earthquake Engineering Research Institute, 24(1): 99–138. [Crossref], [Web of Science ®] , [Google Scholar], Campbell and Bozorgnia, [2008] Campbell, K. W. and Bozorgnia, Y. 2008. NGA ground motion model for the geometric mean horizontal 139 component of PGA, PGV, PGD and 5% damped linear elastic response spectra for periods ranging from 0.01 to 10 s. Earthquake Spectra, Earthquake Engineering Research Institute, 24(1): 139–172. [Crossref], [Web of Science ®] , [Google Scholar], and Chiou and Youngs [2008] Chiou, B. and Youngs, R. R. 2008. An NGA model for the average horizontal component of peak 173 ground motion and response spectra. Earthquake Spectra, Earthquake Engineering Research Institute, 24(1): 173–216. [Crossref], [Web of Science ®] , [Google Scholar], which are shown to be representative of all NGA models, are compared with the Iranian strong-motion database. The database used in this study comprises 863 two-component horizontal acceleration time series recorded within 100 km of epicentral distances for 166 earthquakes in Iran with magnitudes ranging from 4.0–7.4. The comparisons are made using analyses of residuals. The analysis indicates that the NGA models may confidently be applied within the Iranian plateau. To provide more reliable constraint on finite-fault effects and nonlinear site response in the Iranian equations, it would be useful to drive new GMPEs based on a merger of the NGA and Iranian databases.     

Response Sensitivity of Highway Bridges to Randomly Oriented Multi-Component Earthquake Excitation

In two-dimensional and single axis three-dimensional finite element analyses, the ground motion incidence angle can play a significant role in structural response. The effect of incidence angle for three-dimensional excitation and response is investigated in this paper for response of highway bridges. Single-degree-of-freedom elastic and inelastic mean spectra were computed from various orientation techniques and found indistinguishable for combinations of orthogonal horizontal components. Probabilistic seismic demand models were generated for the nonlinear response of five different bridge models. The negligible effect of incidence angle on mean ensemble response was confirmed with a stochastic representation of the ground motions.     

EUROCODE 8 DESIGN RESPONSE SPECTRA EVALUATION USING THE K-NET JAPANESE DATABASE

The Eurocode 8 (EC8) currently proposes two standard shapes for the design response spectra. Type 1 spectra are enriched in long period and are suggested for high seismicity regions. Conversely, Type 2 spectra are proposed for low to moderate seismicity areas (like France), and exhibit both a larger amplification at short period, and a much smaller long period contents, with respect to Type 1 spectra. These propositions, however, were constrained using few events mostly recorded on analogical instruments. In the present study, we use the Japanese high quality digital K-net array in order to evaluate the proposed ECS response spectra. Furthermore, all K-net stations have geotechnical characterisation. We first constructed a database of shallow events, depth less than 25 km, to avoid subduction related records. The database spans six years of seismicity from 1996 until 2003. Thus, 591 events were selected with moment magnitude between 4 and 7.3, recorded at 691 stations, giving a total of 6812 two horizontal components accelerograms. Using these records, we computed spectral ground-motion prediction equations and we used them to review the shape of the proposed EC8 spectra. In particular, we studied the plateau-PGA ratio level, the period interval where this plateau is constant, and site amplification effects. The results show surprisingly that the Type 2 rock better envelope the Japanese data. Another interesting observation is that the K-net data corresponding to all soil classes are rich in short periods around 0.1 s. This characteristic has not been observed in other worldwide databases. Normalised empirical predictions show a widening of the plateau as the soil conditions degrade. This suggests that the Type 2 EC8 spectra do not cover enough the long periods for EC3-soil classes C, D and E. Finally, the computed ground-motion prediction equations show that the peak ground acceleration (PGA) is nearly invariant to the soil conditions. Soil effects are mainly seen in the shape and plateau level.     

Database for Earthquake Strong Motion Studies in Italy

We describe an Italian database of strong ground motion recordings and databanks delineating conditions at the instrument sites and characteristics of the seismic sources. The strong motion database consists of 247 corrected recordings from 89 earthquakes and 101 recording stations. Uncorrected recordings were drawn from public web sites and processed on a record-by-record basis using a procedure utilized in the Next-Generation Attenuation (NGA) project to remove instrument resonances, minimize noise effects through low- and high-pass filtering, and baseline correction. The number of available uncorrected recordings was reduced by 52% (mostly because of s-triggers) to arrive at the 247 recordings in the database. The site databank includes for every recording site the surface geology, a measurement or estimate of average shear wave velocity in the upper 30 m (V_s30 ), and information on instrument housing. Of the 89 sites, 39 have on-site velocity measurements (17 of which were performed as part of this study using SASW techniques). For remaining sites, we estimate V_s30 based on measurements on similar geologic conditions where available. Where no local velocity measurements are available, correlations with surface geology are used. Source parameters are drawn from databanks maintained (and recently updated) by Istituto Nazionale di Geofisica e Vulcanologia and include hypocenter location and magnitude for small events (M < ～5.5) and finite source parameters for larger events.     

Aseismic Assessment of the Qiantang River Levee

Liquefaction potential is evaluated using both in-situ and laboratory testing methods. Liquefaction and dynamic stability for the levee are determined using Biot’s dynamic consolidation equation which is used to analyze the increase and dissipation of pore water pressure as well as liquefaction and dynamic stability in the levee during a magnitude 7 earthquake. By inverse analysis, the acceleration at the bedrock is obtained from the acceleration data monitored previously at free surface and is inputted as the seismic loading. Results presented in this paper can provide improved stability assessment for levees experiencing seismic events of this magnitude.     

Inelastic Demand Spectra of Bi-Linear Models for Capacity Spectrum Method and Response of Simple Structures under Near-Source Records

A very useful tool for the preliminary design of structures is the elastic demand spectrum that can be used in the capacity spectrum method. A pseudo-acceleration relationship has to be assumed when constructing a demand spectrum. This assumption results in large errors for long period structures with large damping ratios and the conventional demand spectra require a substitute elastic structure. In the present study, the conventional demand spectra are extended to bi-linear models. Pseudo-acceleration is still assumed but results in acceptably small errors, when a constant viscous damping coefficient for a single-degree-of-freedom (SDF) structure is calculated from the tangent stiffness and the damping ratio is set at 5% in both elastic and yield phases. For nonlinear structures, tangent stiffness dependency of damping force could be acceptable because energy absorption is primarily the result of structural nonlinear deformation. To extend the conventional demand spectra to a bi-linear model, effective period calculated from the secant stiffness has to be used. The use of effective period introduces no approximation because the peak displacement of the SDF structure is computed from nonlinear analysis in the time domain. The method presented in this study is also valid if damping coefficient proportional to initial elastic spectra is used. In this case, the pseudo-acceleration is defined as the base shear coefficient that is required to produce the peak displacement of the SDF structure in a static manner. We present demand spectra of bi-linear models for a number of near-source records from large earthquakes, and spectral ratios of two horizontal components. The effects of different types of ground motion on the response reduction factor due to inelastic deformation are investigated.     

Generation of Multiple Earthquake Accelerograms Compatible with Spectrum Via the Wavelet Packet Transform and Stochastic Neural Networks

The principal purpose of this article is to present a novel methodology based on wavelet packet transform techniques and stochastic neural networks to generate more artificial earthquake accelerograms from available data, which are compatible with specified response spectra or the design spectra. The proposed method uses the decomposing capabilities of wavelet packet transform on earthquake accelerograms, and the learning abilities of stochastic neural network to expand the knowledge of the inverse mapping from response spectrum to coefficients of wavelet packet transform of earthquake accelerogram. This methodology results in a stochastic ensemble of wavelet packet transform coefficients of earthquake accelerograms and, they are used to the generate accelerograms applying the inverse wavelet packet transform. Finally, an interpretive example is presented which uses an ensemble of recorded accelerograms to train and test the neural network, aiming at the demonstration of the method effectiveness.     

On tidal variability and the existence of planetary wave-like oscillations in the upper thermosphere—II. Non-linear interactions and global scale oscillations

In Part 1 of this paper the variability of diurnal and semidiurnal components of the meridional thermospheric wind was discussed. The observed variability is discussed in the light of the non-linear theory of wave-wave interactions. It is shown that it is possible to explain, at least partially, the variability through the non-linear interactions of tides with long period oscillations having periods between 2 and 15 days. Given that the periods obtained both from the quarterly spectra of the tidal amplitudes and the non-linear interaction analysis coincide with periods reported in the literature for planetary waves in the lower and middle atmosphere, the existence of global scale oscillations are sought in the upper atmosphere. Wave events are observed, coincident with the above-mentioned periods, for a set of five longitudinally distributed locations between 30 and 35 S throughout the yearly samples. The wave events have basically westward phase displacements though eastward travelling phases are observed at times.     

Seismic Hazard Analysis Using Discrete Faults in Northwestern Pakistan: Part I – Methodology and Evaluation

This article is the first of two companion articles that evaluate the seismic hazard in northwestern Pakistan. The area, located at the western edge of the Himalayas, has numerous active faults including the Main Boundary Thrust (MBT) and Main Mantle Thrust (MMT). This article describes the methodology used to perform regional deterministic and probabilistic seismic hazard analyses. Here, seismic sources were defined from 32 identified faults while prior studies have been based on diffuse seismicity and areal source zones. Fault parameters were selected using available data and empirical correlations for faults elsewhere. Recurrence relations were constructed for all discrete faults based on both historical and instrumented seismicity in addition to geologic evidence. Due to lack of region specific attenuation relationships, four plate boundary attenuation relations from the Next Generation Attenuation of Ground Motions Project [Abrahamson et al., 2008 Abrahamson, N., Atkinson, G., Boore, D., Bozorgnia, Y., Campbell, K., Chiou, B., Idriss, I. M., Silva, W. and Youngs, R. 2008. Comparisons of the NGA ground-motion relations. Earthquake Spectra, 24(1): 45–66. [Crossref], [Web of Science ®] , [Google Scholar]] were employed to predict ground motions. Predicted ground motion parameters are compared to measurements from the recent 2005 Kashmir earthquake. In the companion article, the methodology developed and evaluated here is used to conduct deterministic and probabilistic seismic hazard analyses for the entire study region.     

Experimental and Numerical Seismic Response of a 65 kW Wind Turbine

A full-scale shake table test is conducted to assess the seismic response characteristics of a 23 m high wind turbine. Details of the experimental setup and the recorded dynamic response are presented. Based on the test results, two calibrated beam-column finite element models are developed and their characteristics compared. The first model consists of a vertical column of elements with a lumped mass at the top that accounts for the nacelle and the rotor. Additional beam-column elements are included in the second model to explicitly represent the geometric configuration of the nacelle and the rotor. For the tested turbine, the experimental and numerical results show that the beam-column models provide useful insights. Using this approach, the effect of first-mode viscous damping on seismic response is studied, with observed experimental values in the range of 0.5–1.0% and widely varying literature counterparts of 0.5–5.0%. Depending on the employed base seismic excitation, damping may have a significant influence, reinforcing the importance of more accurate assessments of this parameter in future studies. The experimental and modeling results also support earlier observations related to the significance of higher modes, particularly for the current generation of taller turbines. Finally, based on the outcomes of this study, a number of additional experimental research directions are discussed.     

博物馆文物的防震保护研究（二）——设防地震动输入及结构地震动反应

通过对上海及邻近地区地震危害性分析,结合地震研究工作结果,根据上海博物馆文物防震保护的具体要求,研究确定了该博物馆文物防震保护的设防水准及地震动参数。场地地震动输入峰值加速度水准确定为50年超越概率3％,地震动反应谱采用上海市标准《建筑抗震设计规范》(DGJ08-9-92)中给出的地震影响系数曲线(阻尼比0.05),并将输入峰值加速度调整为180gal。研究采用了目前通用的拟合反应谱的方法,通过拟合选定的地震动反应标准谱,合成了6条人造地震波时程曲线,拟合精度控制在相对误差不大于5％;同时结合上海市《建筑抗震设计规范》(DGJ08-9-92)中所附的一条强震记录,共同作为上海博物馆结构地震反应分析的输入地震动。又根据上海博物馆建筑的结构特征分析,结合建筑结沟动力特征的实测结果,通过采用层模型结构时程分析计算方法,计算并获得了在遭遇设防地震时,上海博物馆建筑物每一层的地震动反应,表明上海博物馆建筑各楼层的地震动反应具有明显的楼层放大作用。对各楼层地震动反应的统计分析,给出了上海博物馆建筑物每一层的地震动参数,以此可作为今后文物地震危害性分析,及研究设计隔震装置等防震措施的依据。     

Three Tools for Forecasting Federal Elections: Lessons from 2001

What is the best way to predict Australian federal election results? This article analyses three forecasting tools: opinion polls, economic models, and betting odds. Historically, we find that opinion polls taken close to the election are quite accurate, while economic models provide better medium-run forecasts. The November 2001 federal election largely follows this pattern, although the economic models provided more accurate projections than recorded through the 1990s. Against these, we compare betting odds, analysing a rich data source from one of Australia's largest bookmakers, Centrebet. The betting market not only correctly forecast the election outcome, but also provided very precise estimates of outcomes in a host of individual electorates. Betting fluctuations present an intriguing quantitative record of the shifting fortunes of the campaign. Particularly in marginal seats, the press may have better served its readers by reporting betting odds than by conducting polls. We conclude that the results of these three models can help determine how important the events of August and September 2001 were in deciding the outcome of the election.     

Wavelet-Based Damage Detection in Reinforced Concrete Structures Subjected to Seismic Excitations

The feasibility of using output-only model-free wavelet-based techniques for damage detection in reinforced concrete structures subjected to seismic loads is explored through the analysis of the results of a full scale shake table test of a reinforced concrete bridge column recently performed at the NEES Large High Performance Outdoor Shake Table. The evaluated approaches are based solely in the analysis of the acceleration time histories recorded in the structure. The viability of using numerical models to validate this type of damage detection methodologies is also evaluated. Wavelet analyses were capable of identifying the rebar fracture episodes and partially identified the frequency shifts in the structure as the inelastic demand increased. It was also found that, depending on the methodology employed, the use of numerical models to validate damage detection techniques can oversimplify the actual problem and/or induce spurious irregularities.     

Stochastic Modeling of Earthquake Scenarios in Greater Tehran

Tehran, the capital of Iran, with millions of inhabitants, has been affected several times by historical and recent earthquakes that confirm the importance of seismic hazard assessment for the area. The main objective of this article is to present a probabilistic procedure to construct time series compatible with the source-path and site reflecting the influence of different magnitude events at different distances that may occur during a specified time period. A Monte Carlo approach is used to generate numerous synthetic catalogs for the evaluation of the probabilistic seismic hazard in greater Tehran over hard rock site for a return period of 475 years. The disaggregation of the seismic hazard is carried out to identify hazard-dominating events and to associate them with one or more specific faults, rather than a given distance. The stochastic finite-fault technique based on region specific seismic parameters is used to generate time series of earthquake scenario.     

Fragility Curves for RC Frames Subjected to Tohoku Mainshock-Aftershocks Sequences

The damaging effects of aftershocks are overlooked by current building codes and not properly accounted for in commercial seismic loss assessment software. In this paper, an evaluation of the seismic fragility relationships for reinforced concrete (RC) frame systems prone to mainshock-aftershocks sequences is conducted. Fiber-based finite element models for different types of RC frames are established and subjected to a suite of ground motions obtained from the Tohoku sequence. Fragility relationships are derived with and without consideration to multiple earthquake effects. The results from this study confirm that multiple earthquakes have significant effects on the vulnerability relationships of RC frames.     

Design Earthquake Ground Motion Prediction for Perth Metropolitan Area with Microtremor Measurements for Site Characterization

Perth is the largest city in Western Australia and home to three-quarters of the state's residents. In recent decades, there have been a lot of earthquake activities just east of Perth in an area known as the South-West Seismic Zone. Previous numerical results of site response analyses based on limited available geology information for PMA indicated that Perth Basin might amplify the bedrock motion by more than 10 times at some frequencies and at some sites. Hence, more detailed studies on site characterization and amplification are necessary. The microtremor method using spatial autocorrelation (SPAC) processing is a useful tool for gaining thickness and shear wave velocity (SWV) of sediments and has been adopted in many previous studies. In this study, the response spectrum of rock site corresponding to the 475-year return period for PMA is defined according to the probabilistic seismic hazard analysis (PSHA) based on the latest ground motion attenuation model of Southwest Western Australia. Site characterization in PMA is performed using two microtremor measurements, namely SPAC technique and H/V method. The clonal selection algorithm (CSA) is introduced to perform direct inversion of SPAC curves to determine the soil profiles of representative PMA sites investigated in this study. Using the simulated bedrock motion as input, the responses of the soil sites are estimated using numerical method based on the shear-wave velocity vs. depth profiles determined from the SPAC technique. The response spectrum of the earthquake ground motion on surface of each site is derived from the numerical results of the site response analysis, and compared with the respective design spectrum defined in the Australian Earthquake Loading Code. The comparison shows that the code spectra are conservative in the short period range, but may slightly underestimate the response spectrum at some long period range.     

LOOKING FOR “NEW” EARTHQUAKE DATA IN THE 17th-18th CENTURY EUROPEAN “NEWSSELLERS” NETWORK

This study was started in the frame of an assessment of the completeness of parametric earthquake catalogues. Its primary aim was to check whether early journalistic sources can yield “new” earthquake data, i.e. data on previously unknown damaging earthquakes and previously unknown data on such already known events. Another aim was to assess the quality of the resulting information, an important matter given the widespread opinion that early journalistic sources are highly unreliable. A large sample of monographical (pamphlets) and serial (gazettes) early journalistic sources was systematically searched for “new” earthquake data. The results show them to have a high informative content, while being no more unreliable than most historical sources. It is safe to assume that a large-scale combined effort to put this informative potential within general reach would give a great impetus towards increasing the completeness of the parametric earthquake catalogues of most European (and also non-European) countries.