Site-specific Ground Motion Research Articles

Comparative earthquake loss estimations for high-code buildings in Istanbul

The paper presents the probabilistic and scenario based earthquake loss estimations for the case that the hazard and building inventory inputs are kept the same whereas the damage functions as well as the seismic demand estimation method are changed in an earthquake loss model. Spectral acceleration-displacement based damage assessments by alternating damage functions and inelastic demand evaluation methods are performed for high-code buildings in Istanbul. The buildings are mid- and high-rise, reinforced concrete, moment-resisting frames that are assumed to be designed in accordance with the provisions of Turkish Earthquake Resistant Design Code (1998). Three damage models, i.e. structural capacity and fragility curves, are employed for each building class: Expert judgment based capacity and fragility functions; HAZUS's high-code seismic design level capacity and fragility functions; and Capacity and fragility functions derived based on nonlinear analyses of code complying RC frames. Inelastic spectral displacement demands are computed with three methods: Capacity Spectrum Method, Modified Acceleration-Displacement Response Spectrum Method, and Displacement Coefficient Method. Analyses are realized under site-specific ground motions based on a state-of-the-art hazard model for eight return periods ranging from 100 to 2475 years as well as for an Mw = 7.5 scenario earthquake. Probabilistic loss curves for each case are developed. Estimated average annual losses (AAL) and loss ratios (AALR) are compared. Grid and district based maps illustrating the spatial distributions of estimated long term average losses per year and the loss ratios are presented. The estimated annualized loss ratios at district level in the city are compared to the earthquake insurance premium rates.

Ground Motion Record Selection using Multi-objective Optimization Algorithms: A Comparative Study

Performing time history dynamic analysis using site-specific ground motion records according to the increasing interest in the performance-based earthquake engineering has encouraged studies related to site-specific Ground Motion Record (GMR) selection methods. This study addresses a ground motion record selection approach based on three different multi-objective optimization algorithms including Multi-Objective Particle Swarm Optimization (MOPSO), Non-dominated Sorting Genetic Algorithm II (NSGA-II) and Pareto Envelope-based Selection Algorithm II (PESA-II). The method proposed in this paper selects records efficiently by matching dispersion and mean spectrum of the selected record set and target spectrums in a predefined period. Comparison between the results shows that NSGA II performs better than the other algorithms in the case of GMR selection.

Are the Standard VS-Kappa Host-to-Target Adjustments the Only Way to Get Consistent Hard-Rock Ground Motion Prediction?

Site-specific seismic hazard studies involving detailed account of the site response require the prior estimate of the hazard at the local reference bedrock level. As the real characteristics of such local bedrock often correspond to “hard-rock” with S-wave velocity exceeding 1.5 km/s, “standard rock” PSHA estimates should be adjusted in order to replace the effects of “standard-rock” characteristics by those corresponding to the local bedrock. The current practice involves the computation of scaling factors determined on the basis of VS (S-wave velocity) and “κ0” (site specific, high-frequency attenuation parameter) values, and generally predicts larger high-frequency motion on hard rock compared to standard rock. However, it also proves to be affected by large uncertainties (Biro and Renault, Proceedings of the 15th world conference on earthquake engineering, 24–28, 2012; Al Atik et al., Bull Seism Soc Am 104(1):336–346 2014), mainly attributed to (i) the measurement of host and target parameters, and (ii) the forward and inverse conversions from the response spectrum domain to the Fourier domain to apply the VS and κ0 adjustments. Moreover, recent studies (Ktenidou and Abrahamson, Seismol Res Lett 87(6):1465–1478, 2016) question the appropriateness of current VS − κ0 scaling factors, so that the significant amplification of high frequency content for hard-rock with respect to standard-rock seems overestimated. This paper discusses the key aspects of a few, recently proposed, alternatives to the standard approach. The calibration of GMPEs directly in the Fourier domain rather than in the response spectrum domain is one possibility (Bora et al., Bull Seism Soc Am 105(4):2192–2218, 2015, Bull Earthq Eng 15(11):4531–4561, 2017). Another possibility is the derivation of GMPEs which be valid also for hard-rock conditions (e.g. Laurendeau et al., Bull Earthq Eng 16(6):2253–2284, 2018). In this latter case the host site response is first removed using theoretical site response analyses (and site velocity profile), or generalized inversions techniques. A third possibility is to use existing hard rock surface recordings to derive purely empirical scaling models from standard rock to hard rock (Ktenidou et al., PEER Report, Pacific Earthquake Engineering Research Center, Berkeley, 2016). Finally, when a sufficient amount of records are available at a given site, generic GMPEs can be scaled to the site-specific ground motion using empirical site residual (δS2Ss) (Kotha et al., Earthq Spectra 33(4):1433–1453, 2017; Ktenidou et al., Bulletin of Earthquake Engineering 16(6):2311–2336, 2018). Such alternative approaches present the advantage of a significant simplification with respect to the current practice (with thus a reduced number of uncertainty sources); their generalization calls however for high-quality recordings (including high-quality site metadata) for both host regions and target sites, especially for small to moderate magnitude events. Our answer to the question in the title is thus “No, alternative approaches exist and are promising; though, their routine implementation requires additional work regarding systematic site characterization (for the host regions) and high-quality site characterization/instrumentation (for the target site), and so do also the needed improvements of the existing HTTA procedure”.

Seismic Behaviour of 17th Century Khusro Tomb due to Site-Specific Ground Motion

Introduction:Site Specific time history analysis is performed on a 17thcentury old Khusro Tomb built-in 1622 A.D. by Sultan Nisar Begum. It is a beautiful example of Mughal architecture.Methods:A 3-D finite element model is prepared on Ansys Workbench. Gravity analysis results show the behaviour of Tomb due to its geometry and stress variation is plotted in a form of contour. Modal analysis results show the first three frequencies of Khusro Tombviz., 21.62, 21.68 and 25.38 Hz. In the absence of earthquake record, the stochastic finite fault model is used to generate synthetic site-specific time history to assess the seismic behaviour of the tomb.Results and Conclusion:Time history analysis results shows that the Khusro Tomb's geometrical configuration is adequate to withstand the earthquake due to nearest Allahabad fault. The critical elements of the Tomb are highlighted based on analysis that can be effectively used for the maintenance of the Tomb.

Site effect estimation using Horizontal to Vertical (H/V) spectral ratio technique in Nile Delta, Egypt

ABSTRACTStudy of the seismic wave amplification is very important, as a significant part of damage observed in destructive earthquakes around the world is due to local site effects.The local site effect may cause amplification of seismic waves induced by earthquakes and plays an important role in site-specific ground motion predictions and seismic hazard assessment. The aim of this study is to determine a seismic microzonation by using Nogoshi-Nakamura method experimental technique based on microtremor records. Horizontal to Vertical (H/V) spectral ratios were calculated on Nile Delta at 68 sites using the McSEIS-MT NEO Model 1134 McSEIS-MT NEO instrument. The site effect is typically represented by the resonance frequency (fo) and the associated amplification of ground motion (Ao). The conclusions show the fundamental frequency (fo) ranges from 1.1 to 1.5 at all points, and its corresponding H/V amplitude level (Ao) ranges from 3 to 6.3.

Performance of Buildings Using Site Specific Ground Motion of Kolkata, India

Kolkata, capital of West Bengal, India, is presently congested with moderate to high rise buildings, and may undergo damage during future earthquakes due to the amplification of seismic waves by the soft alluvial soil. Further, most of the buildings are open ground storey (OGS), which is very vulnerable to earthquakes. Therefore, in the present study, the performance of some typical G+1, G+4 and G+9 storied buildings are analyzed using the available site-specific time history of the city by non-linear time history analysis (NLTHA). The analysis has been carried out for maximum considerable earthquake (MCE) and design basis earthquake (DBE) by both considering the stiffness of the infill wall (WI) and without considering stiffness of infill wall (WOI). The result signifies that, in almost all locations, the percentage of roof displacements obtained by site specific time history are more than the Indian codal compatible time history for both WI and WOI. Thus, performance will not be satisfactory for the buildings which are designed according to the Indian seismic code. The present study also corroborates that for almost all the buildings, the ground storey drift remains below immediate occupancy (IO) level during DBE and it varies IO to life safety (LS) level during MCE. However, all the storey drift are below Collapse Prevention (CP) limit. It is to be mentioned that for all the buildings the inter storey drift is higher than the Indian codal (IS-1893 (Part 1):2016) permissible limit (0.4%) during both DBE and MCE. However, the storey drifts result for WI buildings are comparatively lower than WOI buildings which are due to addition of stiffness of infill in each floor and fundamental modal spectral acceleration is lower.

Cost Savings of Implementing Site-Specific Ground Motion Response Analysis in the Design of Short-Period Mississippi Embayment Bridges

Deep dynamic site characterization and a site-specific ground motion response analysis (SSGMRA) were conducted for a bridge site in Monette, Arkansas. The SSGMRA indicated the design acceleration response spectrum determined using the American Association of State Highway and Transportation Officials (AASHTO) general seismic procedure could be reduced by one third for the short-period range due to attenuation of the short-period ground motions. The steel girder pile-bent bridge, originally designed using the AASHTO general seismic design procedure, was redesigned using the updated seismic demands estimated from SSGMRA. A cost-savings analysis was then conducted to determine the potential savings associated with conducting the SSGMRA. By designing based on the results of the SSGMRA, a potential gross savings of $205,000, or 7% of the original bridge construction cost, could be achieved for the study bridge. Items that contributed most to the cost savings were the pile and embankment construction.

Site amplification within the Mississippi embayment of the central United States: Investigation of possible differences among various phases of seismic waves and presence of basin waves

The impact of unconsolidated sedimentary basins on ground motion amplification is of particular interest for earthquake engineers and seismologists. The Mississippi embayment (ME) of the New Madrid seismic zone, located in the central United States, is covered with a thick layer of unconsolidated soil deposits. Thus, the estimation of site response in this region is vital to simulate site-specific ground motions and to conduct site-specific probabilistic seismic hazard analysis. We evaluated site amplification at 11 stations within the ME, employing the horizontal-to-vertical spectral ratio (HVSR) technique.Regarding the results obtained from this study, weak ground motions recorded by stations on the unconsolidated ME sediments are amplified 3–7 times for frequencies less than 5 Hz compared to stations located on bedrock. The fundamental resonant frequencies vary from 0.2 to 0.4 Hz within the ME. We investigated differences between the HVSRs obtained from P-waves, S-waves, coda, and pre-event noise. All fundamental frequencies obtained from different seismic phases are in good agreement with a less than 10% difference. The fundamental frequencies of the P-wave and S-wave are relatively higher due to higher velocity of the P-wave and S-wave compared to other phases since the velocity of seismic waves and fundamental frequencies are proportional. There is a good correlation between the HVSR of the S-wave, coda, and pre-event noise portions for frequencies more than 4 Hz. For the frequencies less than 4 Hz, the HVSR of the S-wave is higher than the HVSR of coda by a factor of 3. Reflections of S-waves from the edges of the unconsolidated sedimentary basin of the ME produce surface waves. The presence of basin-induced surface waves in the coda portion for frequencies less than 3 Hz results in increased amplitude of coda, and as a result, slower decay rate with time implying higher Q values. These basin-induced surface waves have a period of 0.5–4.0 s.

Site-specific earthquake ground motion parameters at the southeastern part of Muscat, Sultanate of Oman

The site-specific earthquake ground motion parameters were presented for the southeastern part of Muscat governorate, including amplification factor at different periods and the values of PGA and spectral accelerations at the surface. The study starts with assessment of the seismic hazard at bedrock level using the probabilistic approach. This assessment was preformed considering an updated earthquake catalogue. The outputs of the probabilistic seismic hazard were uniform hazard spectra for return periods of 475,975 and 2475 years. Spectral matching technique was applied to define the compatible ground motion time series based on the outputs of the probabilistic approach and the deaggregation process. The representative's dynamic soil profiles were determined using the in-situ measurements of compressional and shear waves. The effects of soil deposits on the propagated ground motions time series was evaluated using the equivalent linear analysis in the frequency domain. The final results clarified that, the fundamental site period at the middle coastal parts of the area has the largest values (0.2–0.276 s). The maximum amplification factors found to be 2.76, 2.36, and 2.8 for the periods of PGA, 0.1 s, and 0.2 s, respectively. The values of PGA and spectral accelerations at the surface level are also provided.

Earthquake risk assessment for the building inventory of Muscat, Sultanate of Oman

Earthquake risk can be quantified in terms of the estimated numbers of human casualties and of damaged buildings as well as the monetary losses. The information required for the assessment of earthquake risk in a given region includes the expected level of ground shaking intensity (i.e., the seismic hazard), inventory data for building stock at risk, identification of predominant building typologies and of their vulnerability characteristics, and spatial distribution of number of inhabitants. This study presents an indicative assessment of earthquake risk associated with the building stock in Muscat, the capital city of the Sultanate of Oman. For this purpose, building inventory and demographic data for the city are compiled in GIS environment. The buildings are classified to identify their damageability/vulnerability characteristics, and predominant building typologies are determined. For the estimation of casualties, Muscat population data are further analyzed to calculate number of occupants in the exposed building stock. Spectral acceleration–displacement based damage estimation methodology is implemented for risk calculations. Site-specific ground motions in terms spectral accelerations obtained from the probabilistic seismic hazard assessment for 475- and 2475-year return periods are considered for the representation of earthquake demand in damage analyses. Assessment of damage to buildings and estimation of casualties are obtained using analytical fragility relationships and building damage related casualty–vulnerability models, respectively. Earthquake risk maps illustrating the spatial distribution of number of damaged buildings at different damage states are presented for the considered levels of seismic hazard.

A Site-specific ground-motion simulation model: Application for Vrancea earthquakes

A large number of ground-motion time histories is required for a reliable probabilistic seismic-hazard analysis. However, insufficient ground-motion records has been a major issue in earthquake engineering even in high-seismicity areas. Stochastic and seismological ground-motion models are used to simulate time histories in order to overcome this issue. Many times these models require a large number of records for calibration, are available only for regions with a wealth of data, or fail to characterize well specific sites.The current paper introduces a novel stochastic ground-motion model that allows simulation of realistic non-stationary, non-Gaussian time histories that are statistically consistent with data even at sites with very low numbers of records. This goal is achieved by combining the prior knowledge from a seismological model, calibrated to global data, with the site-specific data within a Bayesian framework. The proposed model uses the specific barrier model as the seismological model and numerical results consistent with records from a nuclear powerplant site in Romania are presented.

A Hybrid Empirical Green’s Function Technique for Predicting Ground Motion from Induced Seismicity: Application to the Basel Enhanced Geothermal System

A method is described for the prediction of site-specific surface ground motion due to induced earthquakes occurring in predictable and well-defined source zones. The method is based on empirical Green’s functions (EGFs), determined using micro-earthquakes at sites where seismicity is being induced (e.g., hydraulic fracturing and wastewater injection during shale oil and gas extraction, CO2 sequestration, and conventional and enhanced geothermal injection). Using the EGF approach, a ground-motion field (e.g., an intensity map) can be calculated for a potentially felt induced event originating within the seismic zone. The approach allows site- and path-specific effects to be mapped into the ground-motion field, providing a local ground-motion model that accounts for wave-propagation effects without the requirement of 3D velocity models or extensive computational resources. As a test case, the ground-motion field for the mainshock (ML = 3.4, M = 3.2) resulting from the Basel Enhanced Geothermal System (EGS) was simulated using only seismicity recorded prior to the event. We focussed on peak ground velocity (PGV), as this is a measure of ground motion on which Swiss norms for vibration disturbances are based. The performance of the method was significantly better than a previously developed generic ground-motion prediction equation (GMPE) for induced earthquakes and showed improved performance through intrinsic inclusion of site-specific effects relative to predictions for a local GMPE. Both median motions and the site-to-site ground-motion variability were captured, leading to significantly reduced misfit relative to the generic GMPE. It was shown, however, that extrapolation beyond units of a couple of magnitude leads to significant uncertainty. The method is well suited to a real-time predictive hazard framework, for which shaking estimates are dynamically updated in light of newly recorded seismicity.

Development of hazard- and amplification-consistent elastic design spectra

In the framework of the definition of a new building code for dams, the Swiss Federal Office for Energy (SFOE) has commissioned a study on the effect of site response variability on elastic design spectra for different soil conditions and seismic hazard scenarios. The goal of the study presented herein is the definition of a new set of site-dependent design spectra for horizontal and vertical ground-motion, whose design shape (scaled to peak ground acceleration) is to be compared with the present Swiss normative (SIA261, revision 2014) [43].To accomplish the task, we have created a large dataset of Fourier-domain seismic amplification functions by collecting empirical observations and site-specific ground motion models from both measured and stochastically generated velocity profiles. Fourier spectra were then converted to response spectral amplification using a combination of spectral modeling techniques and random vibration theory. Average amplification models are thus derived for different soil classes (SIA class A–E), according to the Swiss building code provisions, and for a set of magnitude-distance combinations chosen as representative of the Swiss hazard disaggregation scenario at the Sion site in Switzerland.Finally, the response spectral amplification functions from the database have been combined with the normalized uniform hazard spectra computed at Sion for return periods of 500, 1000, 5000 and 10,000 years. Based on those results, a new set of design spectral shapes is proposed for the different SIA soil classes, accounting for investigated scenario variability and including a reasoned level of conservatism dependent on the distribution of the site-specific amplification models.The proposed methodology targets the reduction in uncertainty associated with seismic design and, although originally focused and applied to the Swiss norm, it could be potentially applied to any national seismic code as a tool for developing, updating or benchmarking the current provisions in a holistic framework.

Ground motion model for reference rock sites in Italy

To assess site-specific ground motion it is common practice to calculate seismic hazard at bedrock and then multiply it by a deterministic site-amplification factor typically computed from 1D numerical simulation. For this reason, the ground motion at bedrock should be free from amplification phenomena and its site response flat. Ground Motion Prediction Equations are generally calibrated using records at stations classified as rock that, however, can be affected by site-effects, caused by peculiar morphological/stratigraphic features.In this work, we propose six proxies based on geological, topographical and geophysical data to identify reference rock sites. We apply these proxies to the same set of recording stations used to derive the most recent ground-motion attenuation model for Italy [6] - ITA10. We find that about half of the analyzed sites, classified as rock on the basis of VS,30 or geological conditions, are unaffected by amplifications and can be actually considered as reference rock sites.Then, we re-calibrate the ITA10 prediction equations for horizontal peak ground acceleration at 20 spectral ordinates in the period range 0.04–2s, accounting for sites that we identify as references rock sites. The resulting reference median values are, on average, 35–40% lower than those calculated by Bindi et al. (2011) model for rock sites. Conversely, the ground motion variability is not significantly changed, even if we introduce a new site soil category to describe the reference rock stations.

Multi-point earthquake response of the Bosphorus Bridge to site-specific ground motions

The study presents the earthquake performance of the Bosphorus Bridge under multi-point earthquake excitation considering the spatially varying site-specific earthquake motions. The elaborate FE model of the bridge is firstly established depending on the new considerations of the used FEM software specifications, such as cable-sag effect, rigid link and gap elements. The modal analysis showed that singular modes of the deck and the tower were relatively effective in the dynamic behavior of the bridge due to higher total mass participation mass ratio of 80%. The parameters and requirements to be considered in simulation process are determined to generate the spatially varying site-specific ground motions. Total number of twelve simulated ground motions are defined for the multi-support earthquake analysis (Mp-sup). In order to easily implement multi-point earthquake excitation to the bridge, the practice-oriented procedure is summarized. The results demonstrated that the Mp-sup led to high increase in sectional forces of the critical components of the bridge, especially tower base section and tensile force of the main and back stay cables. A close relationship between the dynamic response and the behavior of the bridge under the Mp-sup was also obtained. Consequently, the outcomes from this study underscored the importance of the utilization of the multi-point earthquake analysis and the necessity of considering specifically generated earthquake motions for suspension bridges.

Modification of Ground Motions for Use in Central North America

ABSTRACTExisting procedures are used to modify available recorded ground motions to conform to realistic seismic hazard and regional soil conditions for Central North America. Site-specific bedrock ground motions were defined by spectrally-matching select recorded ground motions to conditional mean spectra (CMS) corresponding to a 1000-year return period. Soil profiles developed using existing soil data from the region are used to propagate the bedrock ground motions to the ground surface, for use in dynamic structural analysis. A suite of surface ground motions was developed for locations in southern Illinois; these ground motions are available in an online repository.

Physically based ground motion prediction and validation: a case study medium-size magnitude Marmara Sea earthquakes

The evaluation of realistic time histories for various locations around Marmara Region is aimed to provide reliable input for performance-based seismic design, hazard or risk management studies and developing new seismic standards. The applicability of empirical Green’s functions methodology and physics-based solution of earthquake rupture have been assessed in terms of modeling complex geologic structures. This paper has two main objectives. The first one is to simulate five medium-size magnitude earthquakes (M w ≈ 5.0) recorded in the Marmara Region. A series of synthetic ground motion waveforms for three components are evaluated with a ‘physics-based’ solution of earthquake rupture. The simulation methodology is based on the studies of Hutchings and Wu (J Geophys Res 95:1187–1214, 1990), Hutchings (Seismol Soc Am 81:88–121, 1991; Seismol Soc Am 84:1028–1050, 1994), Hutchings et al. (Geophys J Int 168:569–680, 2007), and Scognamiglio and Hutchings (Tectonophysics 476:145–158, 2009). For each earthquake, we calculate synthetic seismograms by using 500 different rupture scenarios that are generated by Monte Carlo method for a selection of parameters within a range based on prior knowledge of where the earthquakes will occur. The second objective is to validate synthetic seismograms with real seismograms. To improve the credibility of synthetic seismograms from an engineering point of view, the methodology presented by Anderson (in 13th world conference on earthquake engineering, Vancouver, 2003) is followed. This methodology proposes a similarity score based on averages of the quality of fit measuring ground motion characteristics and uses a suite of measurements. In order to compute goodness of fit, ten different ground motion parameters were compared on a scale from 0 to 100, where 100 means perfect agreement. Because the methodology produces source- and site-specific synthetic ground motion time histories, and the goodness-of-fit scores of obtained synthetics are between ‘good’ and ‘excellent’ range (61.128–82.164) based on the Anderson’s score, we conclude that it can be used to produce reliable ground motion time histories for seismic risk regions to develop or improve seismic codes and standards.

Site-Corrected Magnitude- and Region-Dependent Correlations of Horizontal Peak Spectral Amplitudes

Empirical correlations of horizontal peak spectral amplitudes (PSA) are modeled using the total-residuals obtained in a ground motion prediction equation (GMPE) regression. Recent GMPEs moved toward partially non-ergodic region- and site-specific predictions, while the residual correlation models remained largely ergodic. Using mixed-effects regression, we decompose the total-residuals of a pan-European GMPE into between-event, between-site, and event-and-site corrected residuals to investigate the ergodicity in empirical PSA correlations. We first observed that the between-event correlations are magnitude-dependent, partially due to the differences in source spectra, and influence of stress-drop parameter on small and large events. Next, removing the between-site residuals from within-event residuals yields the event-and-site corrected residuals which are found to be region-dependent, possibly due to the regional differences in distance-decay of short period PSAs. Using our site-corrected magnitude- and region-dependent correlations, and the between-site residuals as empirical site-specific ground motion adjustments, we compute partially non-ergodic conditional mean spectra at four well-recorded sites in Europe and Middle Eastern regions. 09_EERI_33_4_Suppl_ES1_Online.xlsx

From Ergodic to Region- and Site-Specific Probabilistic Seismic Hazard Assessment: Method Development and Application at European and Middle Eastern Sites

The increasing numbers of recordings at individual sites allows quantification of empirical linear site-response adjustment factors ( δS2 Ss) from the ground motion prediction equation (GMPE) residuals. The δS2 Ssare then used to linearly scale the ergodic GMPE predictions to obtain site-specific ground motion predictions in a partially non-ergodic Probabilistic Seismic Hazard Assessment (PSHA). To address key statistical and conceptual issues in the current practice, we introduce a novel empirical region- and site-specific PSHA methodology wherein, (1) site-to-site variability ( φS2 S) is first estimated as a random-variance in a mixed-effects GMPE regression, (2) δS2 Ssat new sites with strong motion are estimated using the a priori φS2 S, and (3) the GMPE site-specific single-site aleatory variability σss,sis replaced with a generic site-corrected aleatory variability σ0. Comparison of region- and site-specific hazard curves from our method against the traditional ergodic estimates at 225 sites in Europe and Middle East shows an approximate 50% difference in predicted ground motions over a range of hazard levels—a strong motivation to increase seismological monitoring of critical facilities and enrich regional ground motion data sets.

A Ground Motion Record Selection Approach Based on Multiobjective Optimization

ABSTRACTThe evaluation of the seismic safety and reliability of buildings and building contents within a probabilistic framework often requires response history analyses using site-specific ground motion records. The ground motion selection method proposed in this paper addresses this issue by a stochastic search procedure in which record sets are selected such that first- and second-order statistics (median and dispersion) satisfy predefined ground motion spectrum targets over a wide period range. Once a ground motion record set is selected, it can be used for seismic assessment of a broad class of buildings within the target period range at the given location.