SEISMIC HAZARD IN GREECE BASED ON DIFFERENT STRONG GROUND MOTION PARAMETERS

The available Greek strong ground motion records to date are used in order to study the duration of strong-motion in Greece, covering magnitudes between 4.5 and 6.9 and distances from 1 km to 128 km. An attenuation relation of strong-motion duration is calculated and compared to earlier existing similar relations proposed for Greece and Japan. Furthermore, the seismic hazard for the area of Greece is assessed, using the strong-motion parameters of duration and peak ground acceleration. The results are presented in the form of a map according to which Greece is classified in four different categories of equal seismic hazard.     

Ground-Motion Prediction Equations Based on Data from the Himalayan and Zagros Regions

This study derives ground-motion prediction equations for the horizontal elastic response spectral acceleration for 5% damping for application to the Indian Himalayas. The present equations include a consideration of site category (rock/soil) and style-of-faulting (strike-slip/reverse). Due to a lack of near-field data from India, additional strong-motion data have been included from the Zagros region of Iran, which has comparable seismotectonics to the Himalayas (continental compression). A set of 201 records from 16 earthquakes were used within the regression. The derived model predicts similar ground motions to previously published equations for the Himalayan region but with lower standard deviations.     

Predicting Probabilistic-Based Strong Ground Motion Time Series for Citadel of Arg-E-Bam (South-East of Iran)

The main objective of this article is to present a probabilistic-based strong motion compatible with the source-path and site soil condition given the probability of exceedence for citadel of Arg-e-Bam site bed rock (South-East of Iran). A Fourier amplitude spectral attenuation relation for bed rock beneath the site is proposed which permits the estimation of time-histories through a probabilistic seismic hazard analysis procedure. Due to lack of data, the two well-known simulation techniques, point source and finite fault models have been used for generating hundreds of strong motion as input data. Tens of model parameter values such as stress-drop nucleation points were used, in each specified magnitude-distance, to reduce the uncertainty effects inherently existing in seismological/geological parameters. The proposed attenuation relation is validated by comparing the estimated strong motion, in the form of Fourier amplitude spectral, using the proposed attenuation relation with those of recorded ground motion data at three stations far away from the assumed source so that the results would not be influenced by the near source problems such as directivity and fling step. The results of proposed technique is assessed by comparing the estimated response spectra, with 10% probability of exceedence and 5% damping ratio, with those of traditional uniform hazard spectra. The proposed technique is supposed to be used in retrofitting procedure of international historical adobe structures in Arg-e-Bam site, which have been damaged during the destructive Bam earthquake 2003, Iran     

Estimation of Strong Ground Motions in Southwest Western Australia with a Combined Green's Function and Stochastic Approach

As only a very limited number of earthquake strong ground motion records are available in southwest Western Australia (SWWA), it is difficult to derive a reliable and unbiased strong ground motion attenuation model based on these data. To overcome this, in this study a combined approach is used to simulate ground motions. First, the stochastic approach is used to simulate ground motion time histories at various epicentral distances from small earthquake events. Then, the Green's function method, with the stochastically simulated time histories as input, is used to generate large event ground motion time histories. Comparing the Fourier spectra of the simulated motions with the recorded motions of a ML6.2 event in Cadoux in June 1979 and a ML5.5 event in Meckering in January 1990, provides good evidence in support of this method. This approach is then used to simulate a series of ground motion time histories from earthquakes of varying magnitudes and distances. From the regression analyses of these simulated data, the attenuation relations of peak ground acceleration (PGA), peak ground velocity (PGV), and response spectrum of ground motions on rock site in SWWA are derived.     

AN EVALUATION OF THE STRONG GROUND MOTION RECORDED DURING THE MAY 1, 2003 BINGÖL TURKEY,EARTHQUAKE

An important record of ground motion from a M6.4 earthquake occurring on May 1, 2003, at epicentral and fault distances of about 12 and 9 km, respectively, was obtained at a station near the city of Bingöl, Turkey. The maximum peak ground values of 0.55 g and 36 cm/s are among the largest ground-motion amplitudes recorded in Turkey. From simulations and comparisons with ground motions from other earthquakes of comparable magnitude, we conclude that the ground motion over a range of frequencies is unusually high. Site response may be responsible for the elevated ground motion, as suggested from analysis of numerous aftershock recordings from the same station. The mainshock motions have some interesting seismological features, including ramps between the P-and S-wave that are probably due to near- and intermediate-field elastic motions and strong polarisation oriented at about 39 degrees to the fault (and therefore not in the fault-normal direction). Simulations of motions from an extended rupture explain these features. The N10E component shows a high-amplitude spectral acceleration at a period of 0.15 seconds resulting in a site specific design spectrum that significantly overestimates the actual strength and displacement demands of the record. The pulse signal in the N10E component affects the inelastic spectral displacement and increases the inelastic displacement demand with respect to elastic demand for very long periods.     

Site Classification Assessment for Estimating Empirical Attenuation Relationships for Central-Northern Italy Earthquakes

The aim of this article is to investigate the ground motion attenuation of the most industrialized and populated regions of Italy, evaluating the capability of different approaches to estimate site dependent models. The 5.2 local magnitude earthquake on November 24, 2004 shocked the areas of Northern Italy producing damage of about 215 million euros. The data set, including 243 earthquakes of local magnitude up to 5.2, has been collected in the period December 2002–October 2005 by 30 three-component seismic stations managed by Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano (INGV-MI). Empirical attenuation relationships have been estimated for horizontal peak ground velocity (PGHV), acceleration (PGHA), displacement (PGHD), and for response spectral acceleration (SA) for periods between 0.1 and 1.5 s. To estimate suitable attenuation models, in particular for sites characterized by thick sedimentary geological formations, a soil discrimination based on EU8 code can lead to wrong evaluations. On the contrary, a classification based on H/V spectral ratios of seismic ambient noise (NHV) allows the models to fit better real and predicted data and to reduce the uncertainties of the process. For each receiver, NHV have been strengthened by additional H/V spectral ratio of earthquake data (EHV), calculated considering different portions of the analysed signals. In order to validate the PGHA attenuation relationship for greater magnitudes, accelerometric records, relative to Central-Northern Italy strong motions occurring in the last 30 years, have been collected and superimposed to our attenuation curves.     

A THEORETICAL ATTENUATION MODEL FOR EARTHQUAKE-INDUCED GROUND MOTION

A theoretical attenuation model of earthquake-induced ground motion is presented and discussed. This model is related directly to physical quantities such as source and wave motion parameters. An attenuation formula for rms acceleration of ground motion is derived and verified using acceleration data from moderate-sized earthquakes recorded in Iceland from 1986 to 1997. The source parameters and the crustal attenuation are computed uniformly for the applied earthquake data. Furthermore, attenuation formulas for peak ground acceleration are put forward.     

A NON-PARAMETRIC APPROACH TO ATTENUATION RELATIONS

Abstract

A non-parametric multidimensional regression method is proposed for the prediction of seismic ground motion parameters. The main features which distinguish the method from standard regression procedures are: (1) The relationship between the input and output variables is not selected a priori by a prediction law, (2) an arbitrary number of input variables Can be taken into account, provided that an appropriate data base exists, and (3) the computational procedure is very simple. The results can be easily updated when new information becomes available. The method has been applied for the derivation of attenuation relations by using a combination of databases compiled by other researchers. In the majority of the cases discussed in this paper, the method was used for the prediction of horizontal peak ground acceleration as a function of magnitude and distance. In some cases, ground conditions were also taken into account. Some results on the attenuation relations of peak ground velocity and displacement, as well as Arias intensity, are also presented.     

SOIL-STRUCTURE AND SOIL-STRUCTURE-SOIL INTERACTION: EXPERIMENTAL EVIDENCE AT THE VOLVI TEST SITE

This paper shows the results of two passive experiments carried out at the European Volvi test site where a scaled building has been constructed. The first experiment was performed to study the motion of the structure excited by two small earthquakes. For one month, six strong-motion recorders were installed within the structure, at the top and at the basement. The analysis of the deformation of the structure has been assessed by computing the spectral ratio between the top and the bottom, with a special focus on soil-structure interaction. An analytical model was then proposed to reproduce the structure and soil-structure system behaviour. The soil-structure interaction was accounted for by using impedance functions. During the second experiment, we concentrated our efforts on the effect of the building vibration on the surface ground motion. An explosive shot was fired and several strong-motion recorders were installed on the ground close to the structure that allowed us to clearly identify a monochromatic wave coming from the building, in the time and frequency domains. This experiment allows us to demonstrate the non-negligible effect of the soil-structure-soil interaction that may disturb the surrounding ground motion.     

A PROCEDURE FOR ESTIMATING INPUT ENERGY SPECTRA FOR SEISMIC DESIGN

In this paper, the damage potential of an earthquake ground motion is evaluated in terms of the total power of the acceleration of the ground motion. By assuming an appropriate spectral shape for the input energy spectrum, and using the well-known Parseval theorem for evaluating the total power of a random signal, the peak amplification factor for the equivalent input energy velocity spectrum can be determined. It is shown that the peak amplification factor for the input energy spectrum depends on the peak-ground-acceleration to peak-ground-velocity ratio and duration of the strong motion phase of the ground motion. Values for the equivalent input energy velocity amplification factor vary from about 2 to 10 for most of the recorded ground motions used in this study. Although a considerable scatter of data is observed in this study, the peak amplification factor predicted by the Fourier amplitude spectrum of the ground acceleration provides a fairly good estimate of the mean value of the peak input energy compared to that determined from inelastic dynamic time history analyses, particularly for systems with high damping and low lateral strength. The peak amplification factor derived in this paper provides a more consistent approach for estimation of seismic demand when compared to an earlier empirical expression used for the formulation of duration-dependent inelastic seismic design spectra, even though only a slight difference in the required lateral strength results from the use of the new formula.     

A Comparative Study on Ground Motion Attenuation in the 2012 Varzaghan-Ahar Doublet Event,Northwest of Iran

Predictive capabilities of the four updated NGA ground-motion models (NGA-WEST2) are evaluated in this study for acceleration response spectra using observed ground motions for August 11, 2012 Varzaghan-Ahar events in Iran. The predicted results were compared with those of regional attenuation equations and NGA08 models as well. The results of analyses revealed that the models of NGA-WEST2 improve prediction performance of NGA08 models for the two studied moderate events. All of models underestimate the recorded spectra of the second event for regionally significant period of 0.2 s at source distances below 50 km. For this distance range, almost all of the models underestimate the recorded spectra for periods larger than 1 s.     

Site Classification Using Horizontal-to-vertical Response Spectral Ratios and its Impact when Deriving Empirical Ground-motion Prediction Equations

We classify sites based on their predominant period computed using average horizontal-to-vertical (H/V) response spectral ratios and examine the impact of this classification scheme on empirical ground-motion models. One advantage of this classification is that deep geological profiles and high shear-wave velocities are mapped to the resonance frequency of the site. We apply this classification scheme to the database of Fukushima et al. [2003] Fukushima, Y., Berge-Thierry, C., Volant, P., Griot-Pommera, D. A. and Cotton, F. 2003. Attenuation relation for west Eurasia determined with recent near-fault records from California, Japan and Turkey. Journal of Earthquake Engineering, 7(3): 1–26.  [Google Scholar], for which stations were originally classified as simply rock or soil. The calculation of average H/V response spectral ratios permits the majority of sites in the database to be unambiguously classified. Soft soil conditions are clearly apparent using this technique. Ground-motion prediction equations are then computed using this alternative classification scheme. The aleatoric variability of these equations (measured by their standard deviations) is slightly lower than those derived using only soil and rock classes. However, perhaps more importantly, predicted response spectra are radically different to those predicted using the soil/rock classification. In addition, since the H/V response spectral ratios were used to classify stations the predicted spectra for different sites show clear separation. Thus, site classification using the predominant period appears to be partially mapped into the site coefficients of the ground-motion model.     

FINITE FAULT MODELLING OF NEAR-FIELD ROCK MOTIONS IN THE NEW MADRID SEISMIC ZONE

Due to lack of strong motion records, point-source and finite-fault models have been used to simulate far-field motions at Memphis and St. Louis Cities from earthquake events in the New Madrid Seismic Zone. However, near-field rock motions and their associated uncertainties have never been studied within this zone. The objectives of this study are to develop a simple procedure to account for the uncertainty effect of earthquake source parameters, to analyze the sensitivity of near-field rock motions to input source parameters, and finally, to generate rock motions at two sites located within 11 km from the southwestern segment (strike-fault) and a third site bove the Reelfoot Rift (reverse fault) using a well-validated finite-fault simulation program; FINSIM. An equal-weight logic tree was developed to ensure that the assumed uncertainties are within physical, geological, and seismological constraints. For each site, 100 acceleration time histories with various combinations of parameter uncertainties were respectively simulated for an earthquake of M _w 7.0, 7.5, and 8.0 from each of the two faults. Their average spectral accelerations were in good agreement with those derived from the attenuation relation-ships representative to the Central and Eastern United States. Numerical simulations indicated that spectral accelerations are sensitive to the slip velocity, depth to top of fault, fault strike, slip distribution, and hypocentre location along the strike.     

Spectral Attenuation Relations at Soft Sites Based on Existing Attenuation Relations for Rock Sites

A simple and general method based on well-known random vibration theory is used to compute spectral attenuation relations at soft sites based on existing spectral attenuation relations at rock sites. The method consists of: (1) computation, for given magnitude and distance, of the expected Fourier amplitude spectrum associated with the median rock response spectrum computed with the attenuation relation; (2) inclusion of site effects characterized by a frequency-dependent, linear, or nonlinear transfer function; and (3) computation of the response spectrum at the soft site.     

Vector-valued Intensity Measures Incorporating Spectral Shape For Prediction of Structural Response

Vector-valued ground motion intensity measures (IMs) are developed and considered for efficiently predicting structural response. The primary IM considered consists of spectral acceleration at the first-mode structural period along with a measure of spectral shape which indicates the spectral acceleration value at a second period. For the IM to effectively predict response, this second period must be selected intelligently in order to capture the most relevant spectral shape properties. Two methods for identifying effective periods are proposed and used to investigate IMs for example structures, and an improvement in the efficiency of structural response predictions is shown. A method is presented for predicting the probability distribution of structural response using a vector IM while accounting for the effect of collapses. The ground motion parameter ε is also considered as part of a three-parameter vector. It is seen that although the spectral shape parameter increases the efficiency of response predictions, it does not fully account for the effect of ε. Thus, ε should still be accounted for in response prediction, either through informed record selection or by including ε in the vector of IM parameters.     

Study on Response Spectral Acceleration from the Great Wenchuan,China Earthquake of May 12, 2008

The M _w7.9 Wenchuan earthquake produced a rich set of over 1,400 accelerograms, which helped us to better understand strong ground motions from such a large event. Using the abundant data, we investigated the characteristics of response spectral accelerations from this event. This study includes: the spatial distribution of spectral amplitudes at three periods selected to represent ground motions at short, short-middle, and middle-long period ranges; attenuations of response spectral accelerations at periods between 0.05 and 10 s; comparison between the observed ground motions and predicted motions from empirically based equations [Abrahamson and Silva,1997 Abrahamson, N. N. and Silva, W. J. 1997. Empirical response spectral attenuation relations for shallow crustal earthquakes. Seismological Ressearch Letters, 68: 9–23. [Crossref] , [Google Scholar]; Boore et al., 1997 Boore, D. M., Joyner, W. B. and Fumal, T. E. 1997. Equations for estimating horizontal response spectra and peak acceleration from Western North America earthquakes: a summary of recent work. Seismological Ressearch Letters, 68: 128–153. [Crossref] , [Google Scholar]; Campbell, 1997 Campbell, K. W. 1997. Empirical near-source attenuation relationships for horizontal and vertical components of peak ground acceleration, peak ground velocity, and pseudo-absolute acceleration response spectra. Seismological Ressearch Letters, 68: 154–179. [Crossref] , [Google Scholar]; Huo, 1989 Huo, J. R. Ph.D. 1989. Study on the attenuation laws of strong earthquake ground motion near the source, Dissertation, Institute of Engineering Mechanics, China Earthquake Administration. (In Chinese) [Google Scholar]] commonly used in America and China; comparison between the average response spectra at three distance bins and the Chinese seismic design spectra under major earthquake (with the recurrent interval of over 2,000 years);, the vertical-to-horizontal ratio of response spectra and its dependence on the rupture distance, period, and local site condition; and comparison between the fault-normal and fault-parallel component spectral accelerations within the rupture distance of 60 km. Based on these analyses, we finally drew some conclusions regarding the engineering characteristics of spectral accelerations from large earthquakes, such as Wenchuan of M _w 7.9.     

SEISMIC HAZARD ASSESSMENT IN FLORENCE CITY ITALY

A seismic hazard analysis of Florence city was performed in the frame of a project concerning the dynamic behaviour of cable-stayed bridges. Both a probabilistic approach and a methodology based on the use of a local macroseismic catalogue were applied. A local catalogue was expressly compiled for this purpose, to collect the macroseismic intensities actually observed at the site as a result of past earthquakes. This sort of catalogue is an independent tool to verify the assumptions of the probabilistic approach (seismic zoning, earthquake recurrence relation, attenuation model), though it can supply results in terms of macroseismic intensity only and reflects the effective seismic history at the site, without taking into account any variability. The Cornell' methodology was used to assess probabilistic hazard in terms of macroseismic intensity, peak ground acceleration, peak ground velocity, and pseudovelocity uniform response spectra. The local catalogue points out level VII of the Mercalli-Cancani-Sieberg scale (MCS) as the maximum intensity historically observed in Florence. The probabilistic approach leads to the consideration of intensity VIII MCS as the maximum credible for the city. The probabilistic analysis in terms of ground motion was performed using attenuation relations estimated for alluvium sites, since the geology of Florence area is represented by fluvial and lacustrine deposits of various thickness. Peak ground acceleration values with 90% non exceedence probability in 50 and 500 years are respectively 145 and 219 cm/s's for a shallow alluvium site, and 95 and 157 cm/s's for a deep alluvium site; the corresponding peak ground velocity values for sites located on alluvium are 6.41 and 11.76 cm/s. Uniform response spectra are provided for shallow and deep alluvium sites, according to frequency-dependent attenuation relations estimated from strong Italian earthquakes.     

Attenuation Relationships for Iran

The purpose of this study is to derive the attenuation relationships for PGA, PGV, and EPA parameters for areas within the seismic zones of Zagros, Alborz and Central Iran with rock and soil substructures. In order to do so, at first the available scientific data including the methods used for deriving attenuation relationships and the parameters involved have been gathered. Afterwards, all the efforts have been focused on gathering a thorough catalogue of earthquakes occurred in Iran. In this regard, a majority of the available catalogs in Iran have been gathered and corrected through different methods and finally a set of 89 earthquake events including 307 earthquake records with reliable data was chosen.

Since in order to derive the attenuation relationships it is essential to extract the parameters from the acceleration records, a great effort was placed on gathering the earthquake acceleration records of Iran. This resulted in building a database of a majority of the earthquake records up to the year of 2004. Afterwards, correction methods applicable to earthquakes records of Iran considering the type of machines used and the ground type were examined which resulted in certain guidelines for correction of earthquake acceleration record data related to Iran.

In the next step the needed parameters were extracted from the earthquake acceleration record data which were consequently divided into two seismic zones of Zagros, and Alborz and Central Iran according to tectonic conditions. After examination of the parameters and choosing the most appropriate among them, the attenuation relationships were derived for such parameters.     

Effect of Horizontal Component Definition on the Characterization of Vertical Ground Motions: Application to Eastern Canada

In this article, ground motions recorded on rock sites in eastern Canada are studied in order to characterize their vertical acceleration components. Emphasis is placed on the sensitivity of vertical-to-horizontal spectral ratios to: (i) inter-component intensity correlations and (ii) the use of geometric mean horizontal components at each site instead of considering them individually. Four different definitions of horizontal components are investigated. Vertical-to-horizontal spectral ratios are compared with the findings of other researchers. We illustrate how the results can be used to evaluate vertical acceleration demands on rock sites in eastern Canada.     

An Improved Algorithm for Selecting Ground Motions to Match a Conditional Spectrum

This paper describes an algorithm to efficiently select ground motions from a database while matching a target mean, variance, and correlations of response spectral values at a range of periods. The approach improves an earlier algorithm by Jayaram et al. [2011]. Key steps in the process are to screen a ground motion database for suitable motions, statistically simulate response spectra from a target distribution, find motions whose spectra match each statistically simulated response spectrum, and then perform an optimization to further improve the consistency of the selected motions with the target distribution. These steps are discussed in detail, and the computational expense of the algorithm is evaluated. A brief example selection exercise is performed, to illustrate the type of results that can be obtained. Source code for the algorithm has been provided, along with metadata for several popular databases of recorded and simulated ground motions, which should facilitate a variety of exploratory and research studies.