Response Spectral Ratio Research Articles

Nonlinear seismic response of seabed with terrain variation and seawater-seabed coupling

Understanding the seismic characteristics of submarine sites and conducting seismic response analysis for such locations are crucial for the safety of marine engineering. However, due to a shortage of strong motion records, the ground motion of offshore earthquakes has not yet been fully characterized. The actual seabed conditions are highly intricate, necessitating consideration of factors such as the dynamic coupling effect between seawater and seabed, the strong nonlinearity of seafloor soft sediments, and the diverse nature of natural submarine terrain. In this study, the modified Davidenkov dynamic constitutive model is used to simulate the nonlinear behavior of the soil. The Coupled Acoustic-Structure method is utilized to simulate the interaction between seawater and seabed. Three typical and simplified terrains, namely flat terrain, valley terrain, and hilly terrain, are individually modeled. The measured seafloor ground motions with different frequency components are used as bidirectional seismic excitations input from the bedrock. The amplification factor in terms of CAV is introduced to evaluate the amplification of seismic ground motion characteristics at seabed surface with respect to those at the bedrock surface. The acceleration response spectra in both horizontal and vertical directions, as well as the corresponding vertical-to-horizontal response spectral ratios, at the representative points are obtained, respectively. Several key findings are consistent with the features of the observed offshore and onshore earthquake ground motions. Numerical examples are presented to illustrate the different influence rules of terrain condition, overlying water depth, and seismic intensity on the nonlinear seismic response characteristics.

Overview of Site Effects and the Application of the 2022 New Zealand NSHM in the Wellington Basin, New Zealand

ABSTRACT We provide an overview of the treatment of site effects in the New Zealand National Seismic Hazard Model (NZ NSHM), including a case study of basin effects in central Wellington. The NZ NSHM 2022 includes a change in site parameter from subsoil class (NZS class) to VS30. Poor NZ VS30 characterization is a major source of uncertainty in the NSHM; however, advanced site characterization in Wellington allows for in-depth study. First, we construct a regional 3D shear-wave velocity model and maps of site parameters (T0, NZS class, and VS30) for central Wellington. At central city soil sites, we find the ratios of NZ NSHM 2022 hazard spectra with respect to the current equivalent design spectra range from factors of ∼0.8–2.6 (median ∼1.5), depending on local site conditions and spectral period. Strong amplification peaks at 0.5–2 s are observed in central Wellington. Linear site-specific amplifications from multiple methods are compared at 13 stations and are well-defined by both site-to-site residuals and response spectral ratios relative to station POTS. At many deeper soft sites (VS30<300 m/s), strong amplification peaks occur around T0 that are underpredicted by mean ergodic ground-motion model (GMM) predictions. This underprediction is slightly enhanced when using basin-specific Z1.0 as an additional site parameter. Our study highlights outstanding challenges in modeling strong basin response within shallow basins in NSHMs, including the need to consider region- or basin-specific modeling approaches as well as nonlinear effects at high shaking intensities that dominate the hazard. For New Zealand, in general, as illustrated in the Wellington case study, a priority is the further characterization of VS30 (and VS) for the seismic network to better isolate and quantify uncertainties in seismic hazard and allow useful exploration of regional–GMM adjustments and partially nonergodic approaches.

An offshore non-ergodic ground motion model for subduction earthquakes in Japan Trench area

With the improvement of the world’s largest seafloor observation network (S-net) and the increase in the quantity and quality of records, the ergodic assumptions can be further relaxed in the modeling of offshore ground motion models (GMMs). This allows accounting for systematic and repeatable source, site, and path effects to further understand the characteristics of offshore ground motion in the Japan Trench region. We developed an offshore ergodic backbone GMM for subduction earthquakes and classified the sites into four categories using horizontal–vertical response spectral ratio to investigate site amplification. The offshore ergodic GMM is applicable for subduction earthquake scenarios with moment magnitudes ranging from 4.0 to 7.4 and rupture distances ranging from 10 to 300 km. Comparing offshore ergodic GMMs with onshore GMMs for subduction earthquakes, we found that offshore GMMs were significantly different from onshore GMMs, especially in the long-period and unburied states. Then a new offshore non-ergodic GMM was developed based on the offshore ergodic GMM. The systematic and repeatable source and site effects were captured by the spatially varying coefficients represented by Gaussian processes, while the systematic and repeatable path effects were captured by cell-specific anelastic attenuation proposed by Dawood and Rodriguez-Marek (2013), calculated with the Cohen-Sutherland computer graphics algorithm. The non-ergodic GMM revealed systematic and repeatable source, site, and path effects that were not captured by the ergodic GMM. Moreover, the non-ergodic GMM showed reduced aleatory variability and epistemic uncertainty on ground motion estimation compared to ergodic GMM. The reduction of aleatory variability and epistemic uncertainty had a significant impact on probabilistic seismic hazard analysis. Quantifications of these results are contributed to conduct reasonable seismic design and seismic risk assessment for marine engineering in offshore regions vulnerable to strong subduction earthquakes.

Reducing the uncertainties in the NGA-West2 ground motion models by incorporating the frequency and amplitude of the fundamental peak of the horizontal-to-vertical spectral ratio of surface ground motions

Ground motion models (GMMs) are developed empirically to predict ground motion intensity measures. The site effects in GMMs are usually addressed using time-averaged shear-wave velocity for the upper 30 m of the site (VS30) and shear-wave isosurface depth (i.e. Z1.0 and Z2.5). However, the former does not include the effect of layered soil structure on the site’s response, and the latter is generally inferred. Many studies have shown that site fundamental frequency can be used as an additional site proxy. Using horizontal-to-vertical spectral ratio (HVSR), one can estimate the site fundamental frequency in a fast and inexpensive way. In this article, a model is developed to incorporate site fundamental frequency and its corresponding amplification factor in the Next Generation Attenuation (NGA)-West2 GMMs to reduce the uncertainties. First, a subset of the NGA-West2 database consisting of 14,636 recordings from 298 events is selected after a two-step screening procedure and used to compute the horizontal-to-vertical response spectral ratio (HVSRPSA) of recorded surface ground motions. Second, automated methodologies previously developed by the authors are used to obtain maximum likelihood estimates of site fundamental frequency (fml), its corresponding amplitude (Aml), and associated uncertainties. Third, a mixed-effect maximum likelihood approach is implemented for residual analysis and site-term residual calculation. Finally, an HVSR-based model is developed for the NGA-West2 dataset considering the relationship between site-term residual and the HVSR-based proxies (i.e. fml and Aml). In this model, Aml is as important as fml in reducing the uncertainties. Results show that using a single HVSR-based model can consistently reduce the site-to-site variability ([Formula: see text]) for all NGA-West2 GMMs, which already include the effect of VS30, Z1.0, or Z2.5. Besides, the reduction in [Formula: see text] is period-dependent, with an average of 13% reduction. As a result of the reduction in [Formula: see text], total standard deviation ( σ) decreases by 3.5% on average.

A New Model for Vertical-to-Horizontal Response Spectral Ratios for Central and Eastern North America

ABSTRACT It is a well-known fact that critical structures are required to be designed for the vertical effects of earthquake ground motions as well as the horizontal effects. We developed a new model for the spectral ratio of vertical-to-horizontal components of earthquakes (V/H ratio) for central and eastern North America (CENA). The proposed V/H ratio model has the advantage of considering the earthquake magnitude, source-to-site distance, and the shear-wave velocity of soil deposits in the upper 30 m of the site for peak ground acceleration and a wide range of spectral periods (0.01–10.0 s). The model evaluation is based on a comprehensive set of regression analysis of the compiled Next Generation Attenuation-East database of the available CENA recordings with M ≥ 3.4 and Rrup<1000 km. The median value of the geometric mean of the orthogonal horizontal motions rotated through all possible nonredundant rotation angles, known as the RotD50, is used along with the vertical component to perform regression using the nonlinear mixed-effect regression. We excluded the earthquakes and recording stations in the Gulf Coast region due to their different ground motion attenuation (Dreiling et al., 2014). To compute V/H ratios for the Gulf Coast region, we refer the readers to the study of Haji-Soltani et al. (2017). Moreover, we excluded the National Earthquake Hazard Reduction Program site class E sites from consideration because of their complex site response characteristics and their potential for nonlinear site effects. The predicted V/H ratios from the proposed model are compared with recently published V/H ratio models. We suggest our model to be used for developing the vertical response spectra for CENA sites.

Seismic hazard prediction using multispectral amplification maps in a complex topographic area: A case study of Qiaozhuang town, Sichuan Province, Southwest China

Earthquakes can cause widely distributed slope failures and damage in mountainous areas. The accurate prediction of ground motions in mountainous areas is essential for managing the seismic risk of urban cities near mountains but is restricted primarily by complex seismic site amplification effects in areas of uneven terrain. This study selected Qiaozhuang town located in the Qingchuan—Pingwu fault zone, Southwest China, as a case study. A simulator for mapped seismic responses using a hybrid model (SiSeRHMap) was applied to compute the multispectral seismic topographic amplification maps at the three slope units surrounding Qiaozhuang town (Weigan hill, Mt. Dong, and Mt. Shizi). Post-earthquake damage survey maps, 1D seismic site response spectral ratios, and H/V spectral ratios of earthquake data were used to validate the computed seismic site amplification factors and resonance frequencies. The results suggest that strong topographic amplification effects usually occur at distinct slope locations, such as hilltops, convex slope positions, upslope, and narrow ridges. The computed topographic amplification factors in the study area reached up to 2.4 at upslope or hilltops, and the resonance frequencies were between 3 and 10 Hz. Topographic effects can be as important as stratigraphic effects when assessing seismic amplification effects in the study area. We conclude that both topographic and stratigraphic effects should be considered in the comprehensive seismic hazard assessment of the study area or other similar mountain towns.

Local Geology Effects on Soil Amplification and Predominant Period in Düzce Basin, NW Turkey

Amplification and predominant periods of soils in Düzce Basin were investigated by analysing the data sets of last two major earthquakes and aftershocks of Kocaeli and Düzce earthquakes occurred in 1999 with a magnitude of Mw:7.4 and Mw:7.2, respectively. Two different methods named horizontal/vertical spectral acceleration ratio (HVSAR) and soil-to-rock Response Spectral Acceleration Ratio (RSAR) were used to determine soil amplifications for various periods in Düzce Basin. The data set includes 31 strong gorund motion records from five strong ground motion stations. It was found that the site amplifications at stations are directly related to the local geology underlying the stations. Averaging the residuals between the predicted and observed PGAs resulted in soil amplification from 1.33 to 2.33. The HVSAR method presented soil amplification values between 2.7 and 10 and predominant period values between 0.4 and 0.7 s. Soil amplification values from 1.5 to 14 and predominant periods from 0.5 to 0.8 s were obtained by the RSAR method. High site amplifications and predominant periods mainly depend on the thickness of lithological variances accompanied by low physical and geotechnical properties of alluvial deposits.

Ground accelerations and empirical site classification through H/V response spectral ratio (HVRSR) using historical records from the strong motion network of the Aburrá Valley, Colombia

Using data from the strong motion network of the Aburrá Valley in Colombia, consisting of approximately 24 years of records, we studied the seismic response of 30 sites in the Metropolitan area of the city of Medellín and surrounding municipalities. The network recorded over 240 earthquakes since 1996, with magnitudes between 1.7 and 6.7. The strong motion records indicate a maximum Peak Ground Acceleration (PGA) of 0.05 g (55 gals). We computed the damped 5% response spectra to estimate the soil's natural periods at each site, using the Horizontal-to-Vertical Response Spectral Ratio (HVRSR). The fundamental periods vary from ∼0.1 s to ∼0.5 s, allowing us to perform a first-order characterization of soil rigidity as well as the classification of the soils in five categories. This classification shows a reasonable relationship with the local geology in the Aburrá Valley, which mainly consists of a metamorphic basement, igneous intrusions, and slope and alluvial deposits, with a highly variable degree of mechanical and chemical weathering. The relatively short fundamental periods indicate an absence of soft soils among the station sites, often associated with the largest amplification of seismic waves. The classes identified show spectral amplifications on natural periods, relative to hard-rock, with factors between 2 and 4.5.

Analytical model for response spectral ratio considering the effect of earthquake scenarios

Analytical model for response spectral ratio considering the effect of earthquake scenarios

A Comparative Study of Response and Fourier Spectral Ratios on Classifying Sites

It has been known for decades that predominant periods of soil columns have crucial roles in the evaluation of site effects of ground motion. For this reason, detecting reliable site predominant periods relies upon a diligent data process and frequency domain transform method. In engineering seismology literature, predominant period-based site classifications have been developed to mitigate the local site effects of earthquakes. The main purpose of this study is to investigate the differences between Fourier and response spectral ratios in order to estimate the clear predominant periods and seismic site classes using instrumental accelerogram data. Within this framework, Fourier and response spectra of 26 installed strong ground motion stations in southern Turkey operated by AFAD [T.C. Disaster and Emergency Management Presidency, Strong Ground Motion Database of Turkey (TR-NSMN)] were examined. A total of 527 acceleration records with magnitude ranging from 3 to 5 having shallow crustal depths (0–25 km) and near-field earthquakes (< 150 km) have been analyzed. Elastic response and Fourier spectral ratios of horizontal-to-vertical (H/V) spectra were evaluated for a fair comparison using the S-wave phase. Although there are no significant differences, it was observed in this study that the response spectral ratio’s predominant periods reveal more reliable results for engineering purposes, especially in many sites where Fourier spectra show superficial peaks at engineering bedrock. As a pioneer study for a part of Turkey’s seismic station network, it will be an important step to establish a relationship between response and Fourier spectra to detect the site classes of stations alternatively in a global extent manner in the future.

A Response Spectral Ratio Model to Account for Amplification and Attenuation Effects in the Atlantic and Gulf Coastal Plain

ABSTRACT We used our previously published Lg-wave spectral ratio model to develop a model of pseudospectral acceleration (PSA) response ratios at sites in the Atlantic and Gulf Coastal Plain, relative to a reference site condition defined as the mean response for site locations outside the Coastal Plain. The model is strongly dependent on sediment thickness. The results of this study can be used to predict PSA response, for linear behavior, at sites in the Atlantic or Gulf Coastal Plain with a known thickness of Coastal Plain sediment, given a ground-motion model for reference site conditions outside the Coastal Plain region of the central and eastern United States.

Investigation of Relationship between the Response and Fourier Spectral Ratios Based on Statistical Analyses of Strong-Motion Records

In both seismic design and probabilistic seismic-hazard analyses, site effects are typically characterized as the ratio of the response spectral ordinate on the ground surface to that on the bedrock based on the scaling law borrowed from the Fourier spectral ordinate. Recent studies have shown that different from the Fourier spectral ratio (FSR), the response spectral ratio (RSR) does not purely reflect the site effects but also depends on the earthquake scenario even for linear analysis. However, previous studies are limited to theoretical analysis. This study statistically compares the two spectral ratios by analyzing many actual seismic ground motions recorded at nearby soil and rock sites. It is observed that the average RSR and FSR have similar overall shapes, and their maximum values occur at approximately the same period; however, the values around the peak are clearly different with FSRs consistently exceeding the RSRs. The RSR–FSR relationship depends on the earthquake scenario and the oscillator damping; their difference at periods longer than the site’s fundamental period decreases as the magnitude and epicentral distance increase, and the RSRs generally approach the FSRs as the oscillator damping decreases.

Site classification and probabilistic estimation of Vs30 for the Iranian strong-motion network

Through a probabilistic approach, this study provides estimates of the time-averaged shear-wave velocity in the top 30 m of soil column (Vs30) for the stations of Iranian strong-motion network. For this purpose, we consider the strong-motion dataset of the Road, Housing and Urban Development Research Center for the period 1975–2018 from which 3828 three-component records from 1636 events with moment magnitude of >3, recorded at 892 stations (hypocentral distances of <300 km), are used in this study. The stations with known Vs30 (388 stations) are grouped into the NEHRP site classes; 3 stations in class A, 115 in class B, 213 in class C, 52 in class D, and 5 in class E. We obtain the probability density function and cumulative distribution function of the natural logarithm of horizontal-to-vertical response spectral ratio of ground-motion amplitudes, ln(H/V), at different periods as the basis for site classification and Vs30 estimation. We show that there is a strong dependency between site class and ln(H/V) at periods between 0.5 and 1.4 s. Using two classification criteria, we estimate the site class and Vs30 for 504 stations without this information. Our results show that there are 6 stations in site class A, 191 in class B, 76 in class C, 222 in class D, and 9 in class E. The residuals between observed and estimated Vs30 values (observed − estimated in logarithmic scale) do not show any trends and are consistent across all stations with a mean, standard deviation, and percentage error of 0.09, 0.19, and 15%, respectively. We also test our approach against the values obtained from the topography slope method proposed by Wald and Allen (2007), which results in a larger error with a mean, standard deviation, and percentage error of −0.41, 0.39, and 77%, respectively.

New GMPEs for the Sagami Bay Region in Japan for Moderate Magnitude Events with Emphasis on Differences on Site Amplifications at the Seafloor and Land Seismic Stations of K-NET

ABSTRACTGround-motion prediction equations (GMPEs) for the horizontal and vertical spectral accelerations (SAs) from the offshore area off the Sagami Bay is presented in this article. To compare the ground motions on the seafloor with those at onshore sites, an onshore GMPE was derived for the onshore stations adjacent to the offshore sites and including those in the Kanto basin sites. The offshore dataset includes 738 three-component records, and the onshore dataset includes 3775 records; both datasets are derived from the same set of 233 earthquakes selected for this study. The local site conditions of the offshore sites are investigated by implementing the mean horizontal-to-vertical response spectral ratios because soil condition data are unavailable. Individual site correction terms are used for the offshore sites due to differences among the site conditions, whereas site-class terms are used for the onshore sites based on the travel-time-averaged shear-wave velocity to 30 m (VS30). A comparison between the offshore and onshore models shows that the horizontal SAs for the whole periods and vertical SAs for moderate and long periods of the offshore motions are considerably larger than those of the onshore motions due to the deep deposition layer comprising soft sediment blanketing the seafloor; the vertical SAs of the offshore motions are slightly smaller than those of the onshore motions at short spectral periods. The inconsistency of the vertical motions at short periods may be due to the combined effect of the deposition layer and water layer. However, the vertical site amplification for short periods is independent of the water depth, and the reason of high-frequency deficiency in vertical components need further investigation.

Investigating properties of vertical design spectra in Japan by applying differential evolution to KiK-net data

The vertical design spectrum plays an important role in seismic design whether of critical or ordinary structures. However, many studies focused on the vertical to horizontal response spectral ratio and less researchers investigated the properties of vertical design spectra directly. In this study, differential evolution and simulated annealing are firstly examined to determine an appropriate method to estimate the characteristic parameters of the vertical design spectra. Then, the properties of the vertical design spectra in Japan are investigated by applying differential evolution to about 10000 KiK-net seismic data. Compared with epicentral distance, the influence of earthquake magnitude is more obvious which shows up as the linear correlation between the corner period and earthquake magnitude. Moreover, we propose a loglog exponential formula which relates the corner period of vertical design spectra to that of horizontal design spectra, and the formula may be used in other regions.

Simulation of the Jiuzhaigou, China, earthquake by stochastic finite-fault method based on variable stress drop

An improved stochastic finite-fault method was used to simulate the Mw 6.6 earthquake that occurred on August 8, 2017, in Jiuzhaigou, Sichuan, China. A variation of the stochastic finite-fault method, considering the dynamic corner frequency, was used to overcome the corner frequency. It explains the effect of a given slip distribution on the corner frequency of each subfault. A comparison of the response spectra (damping ratio 5%), spectral ratio (simulated values/observed values), and model deviation demonstrated that the improved corner frequency performs well for the whole periods, especially in short periods from 0.2 to 1 s. Similarly, the revised duration model and the site-amplification factor were applied to simulate the ground motion during the Jiuzhaigou earthquake, and then the response spectra were obtained. The duration of the nine near-field station recordings matched well with the simulated ground motions, and the peak ground acceleration (PGA) of most of the stations matched well with the observed PGA. In the short periods (T < 1 s), a small difference is observed between the simulated response spectra and the observed spectra for most of the stations. However, the response spectra were overestimated within the period range (0.05–10 s). Generally, the simulated ground motions obtained by using the improved model matched well with the observed ground motions, which could be considered the basis for earthquake-resistant design during the postdisaster recovery and the structural dynamic analysis of the Jiuzhaigou region.

Influence of Local Site Condition on Vertical-to-Horizontal Spectrum Ratio – Insight from Site Response Analysis

ABSTRACT A vertical-to-horizontal (V/H) response spectral ratio of 2/3 is commonly adopted in earthquake engineering for assessing the magnitude of vertical motion. However, higher V/H ratios are found in some earthquake records. This study evaluates the factors that can influence the V/H ratio on the basis of vertical and horizontal site response analyses. Two sets of rock motions representing near-source and far-field conditions are propagated through four selected sites that vary in soil column thickness, groundwater table, soil type, and wave velocity profile. The V/H ratio on the ground surface is calculated and compared with that at the bedrock. Results show that the V/H ratio is amplified by the local site effect, and increases at low wave velocity and high intensity of input motion owing to the different nonlinearities presented in the vertical and horizontal directions. The groundwater table considerably varies the V/H ratio and should be considered in assessing the vertical motion or V/H ratio.

Detecting Site Resonant Frequency Using HVSR: Fourier versus Response Spectrum and the First versus the Highest Peak Frequency

ABSTRACTIn this investigation, we examine the uncertainties using the horizontal-to-vertical spectral ratio (HVSR) technique on earthquake recordings to detect site resonant frequencies at 207 KiK-net sites. Our results show that the scenario dependence of response (pseudospectral acceleration) spectral ratio could bias the estimates of resonant frequencies for sites having multiple significant peaks with comparable amplitudes. Thus, the Fourier amplitude spectrum (FAS) should be preferred in computing HVSR. For more than 80% of the investigated sites, the first peak (in the frequency domain) on the average HVSR curve over multiple sites coincides with the highest peak. However, for sites with multiple peaks, the highest peak frequency (fp) is less susceptible to the selection criteria of significant peaks and the extent of smoothing to spectrum than the first peak frequency (f0). Meanwhile, in comparison to the surface-to-borehole spectral ratio, f0 tends to underestimate the predominant frequency (at which the largest amplification occurs) more than fp. In addition, in terms of characterizing linear site response, fp shows a better overall performance than f0. Based on these findings, we thus recommend that seismic network operators provide fp on the average HVSRFAS curve as a priority, ideally together with the average HVSRFAS curve in site characterization.

Spatially correlated vertical ground motion for seismic design

Spatial variation of vertical ground motion may have influence on the response of long span lifeline structures like bridges, pipelines, etc. However, studies specific to the spatial variability of vertical component of ground motion are limited in the literature when compared with the associated horizontal components. Based on the data recorded at SMART1 and LSST arrays, comparison of spatial variability of vertical and horizontal components is explored here using the coherency model reported by the authors elsewhere. Alternatively, Fourier amplitudes of horizontal components are often scaled through an empirical function to estimate that of the vertical components. Ratio of auto-spectral density (ASD) of horizontal to vertical ground accelerations is then investigated using the array recordings. Conditional simulation of spatially varying ground motion (CSSVGM) can be categorized into two different approaches: (i) (evolutionary) cross-spectral density (CSD) based procedures and (ii) auto-spectral density (ASD) based procedure. While the former assumes spatially uniform ASD and accounts only for the phase variability, the latter takes into the account the spatial variability of ASD and thereby accounts for both phase and amplitude variability. These frameworks do not differentiate between horizontal and vertical components. However, the results reported to date by most researchers are based only on the horizontal components. Spatially varying vertical components are next simulated in this paper using both the perspectives and assessed against the array recordings. An attempt has also been made to estimate the SVGM of the vertical components for a future event. Choice of functional form of ASD (of a seed ground motion) on the resulting spatially varying vertical ground motion is also investigated. Finally, empirical forms of vertical to horizontal (V/H) response spectral ratio reported in the prior art do not account for the spatial variability over the footprint of array, which is also investigated here.

Significance of site natural period effects for linear site amplification in central and eastern North America: Empirical and simulation-based models

This article evaluates linear simulation-based and empirical site amplification models including site natural period dependency parameters to account for the distinctive amplification behavior near site fundamental frequencies resulting from the sharp impedance contrast between soil and underlying hard bedrock in central and eastern North America (CENA). The simulation-based amplification models are developed using 581,685 frequency-domain linear analyses generated from a parametric study and include VS30-scaling and site natural period ( Tnat) parameters. The empirical models are derived from residuals analyses of ground-motion models for two reference conditions: B/C boundary ( VS30 = 760 m/s) and CENA hard-rock condition ( VS = 3000 m/s). The simulation-based and empirical models are compared for 8 site profiles in CENA to measured horizontal-to-vertical (H/V) component response spectral (RS) ratios, the mean of linear simulations for similar sites, and one-dimensional (1D) linear site response analysis for four of these sites. Comparisons between observed and estimated site amplification behaviors highlight model dependency on Tnat in CENA. Model consistencies and differences related to the distinct linear amplification features near site fundamental frequency are discussed.