Linear Site Response Research Articles

Peak ground motions and characteristics of nonlinear site response during the 2018 Mw 6.6 Hokkaido eastern Iburi earthquake

The observed peak ground accelerations and peak ground velocities (PGVs) of the 2018 Mw 6.6 Hokkaido eastern Iburi earthquake generally followed the median values from ground motion prediction equations with reasonable errors at fault distances ≥ 50 km. However, at smaller distances, the equations significantly underestimated the peak ground motions, and it was eminent for PGVs. A comparison of surface-to-borehole spectral ratios of S-waves during the mainshock and other events revealed that the sites at smaller distances experienced various degrees of nonlinear site response. The two most widely known characteristics of nonlinear site response are the weakening of higher-frequency components and shifting of predominant frequencies to lower ones in comparison with the linear site response. At one of the sites that recorded the largest intensity of 7 in JMA scale of 0–7, the latter nonlinear effect was so dominant that the ground motions around the new predominant frequency got intensified by one order of magnitude in comparison with that during the weak-motions. Two sites, which were closely located, recorded vertical peak ground accelerations exceeding 1 g for the up-going motions. The recordings showed asymmetric waveforms and amplitudes characteristics of the nonlinear site response in extreme vertical ground motions recorded during a few earthquakes in the past. Few sites having lower vertical peak ground accelerations were also suspected of being experienced nonlinear site response on vertical motions. These findings suggest taking a cautious approach to enumerate the reduction in amplification at higher frequencies using the single-station horizontal-to-vertical (H-to-V) spectral ratio technique. However, we found that the H-to-V technique was still useful to detect nonlinearity. Finally, an ad hoc equation was derived to correct the nonlinear site amplification in predicting horizontal PGVs with respect to one of the most widely used attenuation models in Japan. The results indicated that the effect was much stronger for a larger input motion than that for a proportional change in the Vs30 values.

Site Amplification Functions for Central and Eastern North America – Part I: Simulation Data Set Development

This paper presents the development of large-scale simulation-based data sets used to inform new site amplification models for Central and Eastern North America (CENA). Linear elastic, equivalent linear, and nonlinear one-dimensional site response simulations of site conditions in CENA are employed. An analysis tree is introduced to capture the range of expected CENA geologic conditions. Independent variables include the following: (1) representative and random shear wave velocity ( VS) profiles using data from the literature; (2) randomized, nonlinear shear modulus reduction and damping vs. shear strain curves with constraint on soil shear strength; and (3) outcrop ground motions representative of the VS= 3,000 m/s CENA reference rock condition. The resulting database of 1,747,278 simulations is conditioned on several parameters relevant to site amplification, which facilitates model development that is the subject of a companion paper. The database is openly available for use by other researchers.

An investigation on the evaluation of dynamic soil characteristics of the Elazig City through the 1-D equivalent linear site-response analysis

Consideration of the effects of the site response in the design of civil structures systems is of important to mitigate the damages to a certain extent on structures and the environment. Hence, it is relatively crucial to reliably attain the dynamic soil parameters of an earthquake-prone city/state. In the current study, a comprehensive investigation on the dynamic soil properties of the city of Elazig with very close proximity to the East Anatolian Fault Zone (EAFZ) having a high potential of producing destructive earthquakes is carried out. Performing probabilistic seismic hazard analysis (PSHA), the moment magnitude of the city is determined as Mw = 7.7 according to 10% probability of exceedance in 50 years. Bedrock-level acceleration spectra is developed utilizing different attenuation relationships for the city, and 1-D equivalent linear site response analysis is conducted on an example soil profile of the city through the SHAKE2000 software considering 16 earthquake motions recorded at the bedrock level. Local surface acceleration spectra obtained from the analysis are then compared to the design spectra of the Turkish Seismic Code for Buildings (TSCB) and Eurocode-8 (EC8) in an attempt to identify the difference between the code spectra and local surface spectra. In addition, in situ geotechnical tests of standard penetration and seismic refraction are conducted at different locations of the study area. Incorporating the results from the field tests into the site response analysis, the soil amplification factor, predominant soil period, peak ground acceleration and spectral maps for the period of T = 0.2 and T = 1.0 s are obtained for the study area. The outcomes from the analysis reveals that structures with higher vibration period than T = 1.0 s are subjected to lower spectral acceleration (Sa), whereas higher Sa values can be used for those with a vibration period lower than T = 0.2 s.

Sensitivity analysis of geotechnical site conditions effect on the seismic response of a saturated inhomogeneous poroviscoelastic soil profile

PurposeThis paper aims to present the investigation of the linear and nonlinear seismic site response of a saturated inhomogeneous poroviscoelastic soil profile for different soil properties, such as pore-water saturation, non-cohesive fines contentFC, permeabilityk, porositynand coefficient of uniformityCu.Design/methodology/approachThe inhomogeneous soil profile is idealized as a multi-layered saturated poroviscoelastic medium and is characterized by the Biot’s theory, with a shear modulus varying continuously with depth according to the Wichtmann’s model. Seismic response analysis has been evaluated through a computational model, which is based on the exact stiffness matrix method formulated in the frequency domain assuming that the incoming seismic waves consist of inclinedP-SVwaves.FindingsUnlike the horizontal seismic response, the results indicate that the vertical one is strongly affected by the pore water saturation. Moreover, in the case of fully saturated soil profile, the same vertical response spectra are found for the two cases of soil behavior, linear and nonlinear.Originality/valueThis research is a detailed study of the geotechnical soil properties effect on the bi-directional seismic response of saturated inhomogeneous poroviscoelastic soil profile, which has not been treated before; the results are presented in terms of the peak acceleration ratio, as well as the free-field response spectra and the spectral ratio (V/H).

Evaluation of the site amplification factors estimated by equivalent linear site response analysis using time series and random vibration theory based approaches

The objective of this study is to estimate and compare the site amplification factors (AFs) using two different one dimensional (1-D) equivalent-linear (EQL) site response analysis approaches: the time series (TS) approach and the random vibration theory (RVT) based method. For this purpose, random soil profiles combined with different soil types, EQL soil properties, and unit weights are tested at several input ground motion levels. Analysis results showed that the AFs estimated by the TS-approach are systematically higher than the AFs estimated by the RVT-based method in the short period range (T < 0.5 s), especially when the bedrock peak ground acceleration is higher than 0.2 g. The relative difference between the AFs estimated in both methods is most prominent in granular soils: differences reach up to 35–40% compared to 10–15% for clays. On the other hand, the AFs calculated in this study are in good agreement with the empirical AF models utilized in recent ground motion models, indicating that the RVT-based AF models may be preferred in the future to cover a larger range of scenarios than the empirical datasets.

Equivalent linear computation of response spectra for liquefiable sites: The spectral interpolation method

A simplified methodology is presented for the computation of elastic response spectra at liquefiable sites, based on the widely used equivalent linear site response analysis method. The target response spectrum is obtained by frequency dependent interpolation between the response spectra for “non-liquefied” and for “liquefied” ground, the former computed for the native soil properties, without excess pore pressure buildup, and the latter for the properties of the liquefied soil. Apart from the structural frequency, the interpolation coefficient is also related to the factor of safety against liquefaction. In this way, the proposed methodology takes indirectly into account the initial segment of the seismic excitation time-history, until the onset of liquefaction, which is of cornerstone importance for the overall ground response at sites with low and moderate liquefaction potential. Results of parametric nonlinear numerical analyses and three field case studies are used to calibrate the methodology and evaluate its accuracy. In addition, the potential of the proposed methodology for defining code-oriented design spectra for liquefiable sites is examined.

Effect of uncertainty in $$V_{\mathrm{S}}{-}N$$ V S - N correlations on seismic site response analysis

This paper studies the reliability of the calculated shear-wave velocity ( $$V_{\mathrm{S}}$$ ) from different available $$V_{\mathrm{S}}$$ and SPT-N correlations in terms of seismic site response analysis. In the present study, various $$V_{\mathrm{S}}$$ –N correlations developed for different regions around the globe have been used to calculate the bound of $$V_{\mathrm{S}}$$ variations with depth at three different sites in Kolkata city. This bound has later been used to generate the random $$V_{\mathrm{S}}$$ profiles using the Monte Carlo simulation. Equivalent linear site response analysis has been performed to study the response of those generated profiles under different input motion excitations. Strong-to-weak ground motion records have been used for this purpose. The amplification spectra of the generated $$V_{\mathrm{S}}$$ profiles using all soil types and specific soil-type $$V_{\mathrm{S}}$$ –N correlations show significant variations. The study also shows that the $$V_{\mathrm{S}}$$ –N correlation may result in quite different $$V_{\mathrm{S},30}$$ values and subsequently it may lead to the different site classes according to the NEHRP 2003 classification. So, the random choice of the $$V_{\mathrm{S}}$$ –N correlation, where the direct measurement of $$V_{\mathrm{S}}$$ is not available, may affect the outcome of seismic hazard analysis significantly. The study points out the need for accurate estimation of the $$V_{\mathrm{S}}$$ profile either from in-situ determination or using site-specific correlation.

On linear site amplification behavior of crustal and subduction interface earthquakes in Japan: (1) regional effects, (2) best proxy selection

A strong-motion database is compiled from KIK-Net Archive of Japan (kyoshin.bosai.go.jp) with following criteria: shallow crustal and subduction interface events between 2000 and 2016, recorded within 300 km and moment magnitude, Mw range is 4.9–7. Time-based average of shear-wave velocity profiles up to different depths 10 m (VS10), 20 m (VS20), 30 m (VS30) and 50 m (VS50) are computed. Only stations with 200 < VS30 < 1500 m/s and the shear-wave velocity (Vs) profiles of the site reaches 800 m/s (h800) are used. Then ground-motion prediction equations for crustal and interface earthquakes are generated for surface motions, borehole motions, and surface-to-borehole spectral ratios (SBSR). The linear site response effect in surface motion equations are modeled in terms of h800 and site proxies: VS10, VS20, VS30, and VS50. The borehole-motion and SBSR models use Vs at borehole depth, and impedance ratio and h800, respectively. The crustal earthquakes generally produce higher ground-motions than interface events at rock site. The site behavior of crustal and interface earthquakes are found statistically different. The difference in short-period site factor is not more than 5%, whereas, at long-period site factor, crustal motions are amplified 13% more than interface motions. Applying the borehole motion and SBSR models, the estimated surface motions are compared with observed surface motions. The misfit is generally found less than 6%. It is concluded that SBSR can be a good indicator for site-specific amplification. Simple inference test is applied to the between-site residuals of surface motion and SBSR models to understand the regional variations in site amplification. In the point of site amplification, the interface earthquakes are more sensitive to regional effects than crustal earthquakes. The comparisons of between-site residuals and site amplification estimates computed with alternative site proxies reveal that at short periods VS20 is sufficient to predict the site response; however, as the period increases the performance of VS50 proxy becomes the best.

Evaluation of site effects on ground motions based on equivalent linear site response analysis and liquefaction potential in Chennai, south India

We study local site effects with detailed geotechnical and geophysical site characterization to evaluate the site-specific seismic hazard for the seismic microzonation of the Chennai city in South India. A Maximum Credible Earthquake (MCE) of magnitude 6.0 is considered based on the available seismotectonic and geological information of the study area. We synthesized strong ground motion records for this target event using stochastic finite-fault technique, based on a dynamic corner frequency approach, at different sites in the city, with the model parameters for the source, site, and path (attenuation) most appropriately selected for this region. We tested the influence of several model parameters on the characteristics of ground motion through simulations and found that stress drop largely influences both the amplitude and frequency of ground motion. To minimize its influence, we estimated stress drop after finite bandwidth correction, as expected from an M6 earthquake in Indian peninsula shield for accurately predicting the level of ground motion. Estimates of shear wave velocity averaged over the top 30 m of soil (VS30) are obtained from multichannel analysis of surface wave (MASW) at 210 sites at depths of 30 to 60 m below the ground surface. Using these VS30 values, along with the available geotechnical information and synthetic ground motion database obtained, equivalent linear one-dimensional site response analysis that approximates the nonlinear soil behavior within the linear analysis framework was performed using the computer program SHAKE2000. Fundamental natural frequency, Peak Ground Acceleration (PGA) at surface and rock levels, response spectrum at surface level for different damping coefficients, and amplification factors are presented at different sites of the city. Liquefaction study was done based on the VS30 and PGA values obtained. The major findings suggest show that the northeast part of the city is characterized by (i) low VS30 values (< 200 m/s) associated with alluvial deposits, (ii) relatively high PGA value, at the surface, of about 0.24 g, and (iii) factor of safety and liquefaction below unity at three sites (no. 12, no. 37, and no. 70). Thus, this part of the city is expected to experience damage for the expected M6 target event.

Linear and nonlinear site response analyses to determine dynamic soil properties of Kirikkale

In order to make reliable earthquake-resistant design of civil engineering structures, one of the most important considerations in a region with high seismicity is to pay attention to the local soil condition of regions. It is aimed in the current study at specifying dynamic soil characteristics of Kirikkale city center conducting the 1-D equivalent linear and non-linear site response analyses. Due to high vulnerability and seismicity of the city center of Kirikkale surrounded by active many faults, such as the North Anatolian Fault (NAF), the city of Kirikkale is classified as highly earthquake-prone city. The first effort to determine critical site response parameter is to perform the seismic hazard analyses of the region through the earthquake record catalogues. The moment magnitude of the city center is obtained as Mw=7.0 according to the recorded probability of exceedance of 10% in the last 50 years. Using the data from site tests, the 1-D equivalent linear (EL) and nonlinear site response analyses (NL) are performed with respect to the shear modulus reduction and damping ratio models proposed in literature. The important engineering parameters of the amplification ratio, predominant site period, peak ground acceleration (PGA) and spectral acceleration values are predicted. Except for the periods between the period of T=0.2-1.0 s, the results from the NL are obtained to be similar to the EL results. Lower spectral acceleration values are estimated in the locations of the city where the higher amplification ratio is attained or vice-versa. Construction of high-rise buildings with modal periods higher than T=1.0 s are obtained to be suitable for the city of Kirikkale. The buildings at the city center are recommended to be assessed with street survey rapid structural evaluation methods so as to mitigate seismic damages. The obtained contour maps in this study are estimated to be effective for visually characterizing the city in terms of the considered parameters.

Site response analysis of vertical ground motion in consideration of soil nonlinearity

Vertical ground motion significantly affects the seismic response of engineering structures, particularly nuclear power plants and dams. However, most ground motion predictions or site response analyses focus on horizontal ground motion. As a result, knowledge of the characteristics of vertical ground motions is inadequate. In this study, a benchmark approach for equivalent linear vertical site response analyses is developed, with focus on the modeling of soil nonlinearity. The modeled soil exhibits different nonlinear behavior in the vertical direction depending on the saturation condition (i.e., above or below the groundwater table). Moreover, the vertical nonlinearity is different from that observed in the horizontal direction. The vertical ground responses predicted by the proposed approach are generally consistent with downhole measurements associated with different geological conditions, groundwater tables, and shaking intensities.

Selection of representative shear modulus reduction and damping curves for rock, gravel and sand sites from the KiK-Net downhole array

Representative computation of ground response parameters requires accurate information about nonlinear dynamic behavior of the soil column, commonly incorporated in site response analysis through shear modulus reduction and damping curves which are functions of the strain level. Most site response studies are carried out by considering a set of existing shear modulus and damping curves, without knowing its suitability for the in situ soil type. In this study, an attempt has been made to identify suitable shear modulus and damping curves for soil grouped into different classes viz. sand, gravel and rock. Soil profiles of sites having surface and bedrock motion recordings are selected from the KiK-Net downhole array database and equivalent linear and total stress nonlinear site response analysis has been carried out by varying the shear modulus and damping curves for different sites. Estimated surface response spectra for each set of shear modulus and damping curves are compared with the observed response spectra at each site, and a detailed analysis is made to find out which set of curves gives a best match with the recorded data. Based on this study, representative property curves for rock, gravel and sand are suggested, which could be used for further site response studies in the region. This study shows that only a set of shear modulus and damping curves ensure a compatible spectrum with the recorded data from the KiK-Net downhole array sites, among the many available shear modulus and damping curves in the literature.

Newly Developed MATLAB Based Code for Equivalent Linear Site Response Analysis

Characteristics of ground motions generated during an earthquake (EQ) alter between bedrock and the surface depending upon subsoil properties. Such modifications in the ground motion characteristics are termed as local site effects. Building response as well as induced effects of EQs are thus controlled by these modified ground motions at the surface. Hence, addressing the local site effect known as site response analysis is of considerable importance for any region. Numerically, site response analysis can be performed using linear, equivalent linear and nonlinear methodologies. Amongst these three methodologies, equivalent linear method of site response analysis is widely followed because of its simplicity and reasonable accuracy. At present, there are numerous softwares and codes which can perform site response analysis following equivalent linear methodology. Some of these softwares are; SHAKE2000, EERA and DEEPSOIL. In this work, a new MATLAB code is developed which can perform equivalent linear site response analysis in the frequency domain. New code is developed in such a way that the response in user specified layers can be shown together for better comparison and understanding. All the response parameters (Fourier spectrum, strain time history, amplification spectra, acceleration time history etc.) are shown in a single window so that the user can compare amongst them. Further, the numerical values of these response parameters can be obtained easily. In addition, limitation of underestimating high frequency ground motion by available equivalent linear analysis tool is overcome in the newly developed code. In order to validate the newly developed code, site response analyses carried out for a typical borehole using SHAKE2000 and newly developed code are compared and found closely matching.

A comparative study on Soil Properties and Applications Review with EERA and NERA in İstanbul-MARMARAY Project between Kazlıçeşme to Sirkeci

Over the course of history Marmara region in North-western Turkey has been the site of numerous destructive earthquakes. Based on historical and instrumental earthquake records, the Marmara sea region is one of the most seismically active regions of the Eastern Mediterranean. The Marmara region is under the influence of the western part of the North Anatolian Fault Zone (NAFZ) and the N-S extensional regime of Western Turkey. Therefore, the earthquake risk analysis is very important for the MARMARAY Project. 76 km-long MARMARAY Project is an important project not only for Turkey but also for the world because it joins the two continents through railway. It will also serve for a comfortable and healthy way of environment, providing a contemporary solution for urban transportation. Geotechnical and geological parameters of the region were obtained from analyses of seven boreholes. In this paper, using average wave velocities in layers, thickness, density and formation data based on the PS logs, 43 m and 65.5 m depths ranging from 7 different boring logs in a ground-wise different geological regions in Istanbul, ground response functions were obtained. Based on the soil profiles transferred to EERA (Equivalent - Linear Earthquake Site Response Analyses of Layered Soil Deposits) and NERA (Nonlinear Earthquake Site Response Analyses of Layered Soil Deposits) softwares, the rock soil record of August 17, 1999 Kocaeli earthquake in Istanbul – Besiktas Ministry of Public Works and Settlement (IBMPWS), response and design spectrums that may be considered crucial in case of an earthquake were obtained. The acceleration record was used as an input motion having PGA value of 0,04287 g (east-west component) which was applied on sublayers (i.e. sand, gravel, clay) using EERA and NERA programs. The analysis is done by keeping constant damping ratio of 5%. Also nonlinear analysis was compared with the linear method of analysis. Stages involved in ground response analyses to develop site-specific response spectra at a soil site are summarized. Some of the known site response analysis methods are summarized and similarities and differences between linear and nonlinear methods.

Impact of Higher Frequency Content of Input Motion Upon Equivalent Linear Site Response Analysis for the Study Area of Delhi

While travelling through the subsoil layers, earthquake generated bedrock motions get modified significantly due to local soil and should be quantified using ground response analysis. Present study concentrates on equivalent linear method of site response analysis in SHAKE2000 software. It is a frequency based analysis tool having default frequency set to 15 Hz. While due consideration is given to amplitude, no to very limited information about the frequency content of the input motion to be considered in ground response analysis is available. In the present work, the effect of the maximum frequency of ground motion in site response analysis using SHAKE2000 is examined. Two sets of analyses are carried out in this work based on 30 globally recorded input motions. In the first analyses, input motion up to 15 Hz maximum frequency, which is a default value in SHAKE2000 is considered while second analyses are based on considering each of the 30 input motions up to the Nyquist frequency. Comparing the results from the two sets of analyses highlight that selection of maximum frequency in SHAKE2000 has considerable effect in ground motion amplification at different depths. As a result, even the peak ground acceleration which controls the building behavior and damage scenario, is going to change considerably even in case same input motion is used in the analysis.

Equivalent Linear Computation of Response Spectra for Liquefiable Sites: The Spectral Envelope Method

AbstractA simplified methodology is proposed for the computation of elastic response spectra at liquefiable sites, based on the widely used equivalent linear (frequency domain) site response analysis method. The actual response spectrum is obtained as the upper-bound envelope of the thus calculated response spectra corresponding to the preliquefaction and the postliquefaction segments of the seismic excitation, the former computed for the natural soil properties and the latter for the properties of the liquefied soil. The time of liquefaction onset, which separates the two seismic excitation segments, is defined in terms of the minimum factor of safety against liquefaction within the liquefiable layer. Additional guidelines are provided for the estimation of the excess pore pressure buildup and the associated soil softening during the preliquefaction segment of the seismic excitation, as well as for the definition of the liquefied soil stiffness and the hysteretic damping ratio. The proposed methodology h...

Comparison of Equivalent Linear and Nonlinear Site Response Analysis Results and Model to Estimate Maximum Shear Strain

We compared the results of equivalent linear (ELA) and nonlinear site response analyses (NLA) and found that the differences between the values of the peak ground acceleration ( PGA), peak ground velocity ( PGV), Arias intensity ( I a), significant duration ( D5–75), and response spectrum for periods between 0.025 s and 2 s predicted by each method are non-negligible for maximum shear strain values predicted by ELA ( γ max, ELA) greater than 0.04% to 1.0%. As γ max, ELA increases, ELA in general predict smaller shear strain and D5–75 values, and larger PGA, PGV, I a, mean period, and response spectral values for periods less than 0.1 s and periods near the natural site period than NLA. To help researchers and practitioners decide when to use ELA and/or NLA, we developed a model to estimate γ max, ELA before conducting a site response analysis.

Comprehensive Comparison among the Campbell–Bozorgnia NGA‐West2 GMPE and Three GMPEs from Europe and the Middle East

Campbell and Bozorgnia (2006) compared their newly developed Next Generation Attenuation‐West1 project (NGA‐West1) ground‐motion prediction equation (GMPE) with a contemporary GMPE developed for the active crustal region of Europe and the Middle East. Based on that comparison, they proposed that their GMPE could be used to estimate ground motions in these regions. Later studies by a number of investigators confirmed this proposal for several of the NGA GMPEs using available pan‐European GMPEs and European strong‐motion data. In this study, I performed a detailed comparison of the NGA‐West2 GMPE of Campbell and Bozorgnia (2014) with three newly developed GMPEs for the pan‐European region. The comparisons were performed in terms of median predictions, standard deviations, and residual analyses with respect to the NGA‐West2 database used to develop the NGA‐West2 GMPE. These comparisons indicate that the scaling characteristics of all four GMPEs are generally comparable in terms of attenuation and linear site response but differ in terms of scaling with magnitude, source depth, style of faulting, and nonlinear site effects. These differences are not scientifically significant and are not found to be statistically significant for the pan‐European events of similar magnitude in the NGA‐West2 database. As a result, I propose that the GMPE of Campbell and Bozorgnia (2014) can be used to estimate ground motions from moderate‐to‐large‐magnitude earthquakes in pan‐Europe as a means of more reliably extending these estimates to large magnitudes and short distances of greater engineering interest and to include ground‐motion scaling features that are not currently included in pan‐European GMPEs.

Challenges associated with site response analyses for soft soils subjected to high-intensity input ground motions

Nonlinear site response analyses are generally preferred over equivalent linear analyses for soft soil sites subjected to high-intensity input ground motions. However, both nonlinear (NL) and equivalent linear (EQL) analyses often result in large shear strain estimates (3–10%) at soft sites, and these large strains may generate unusual characteristics in the predicted surface ground motions, such as irregular time histories and atypical spectral shapes. One source of unusual ground motion predictions may be attributed to unrealistically low shear strengths implied by commonly used modulus reduction curves. Therefore, modulus reduction and damping curves can be modified at shear strains greater than approximately 0.1% to provide a more realistic soil model for site response. However, even after these modifications, nonlinear and equivalent linear site response analyses still may generate unusual surface acceleration time histories and Fourier amplitude spectra at soft soil sites when subjected to high-intensity input ground motions. In this study, we use equivalent linear and nonlinear 1D site response analyses for the well-known Treasure Island site to demonstrate challenges associated with accurately modeling large shear strains, and subsequent surface response, at soft soil sites.

Soil amplification with a strong impedance contrast: Boston, Massachusetts

In this study, we evaluate the effect of strong sediment/bedrock impedance contrasts on soil amplification in Boston, Massachusetts, for typical sites along the Charles and Mystic Rivers. These sites can be characterized by artificial fill overlying marine sediments overlying glacial till and bedrock, where the depth to bedrock ranges from 20 to 80m. The marine sediments generally consist of organic silts, sand, and Boston Blue Clay. We chose these sites because they represent typical foundation conditions in the City of Boston, and the soil conditions are similar to other high impedance contrast environments. The sediment/bedrock interface in this region results in an impedance ratio on the order of ten, which in turn results in a significant amplification of the ground motion. Using stratigraphic information derived from numerous boreholes across the region paired with geologic and geomorphologic constraints, we develop a depth-to-bedrock model for the greater Boston region. Using shear-wave velocity profiles from 30 locations, we develop average velocity profiles for sites mapped as artificial fill, glaciofluvial deposits, and bedrock. By pairing the depth-to-bedrock model with the surficial geology and the average shear-wave velocity profiles, we can predict soil amplification in Boston. We compare linear and equivalent-linear site response predictions for a soil layer of varying thickness over bedrock, and assess the effects of varying the bedrock shear-wave velocity (VSb) and quality factor (Q). In a moderate seismicity region like Boston, many earthquakes will result in ground motions that can be modeled with linear site response methods. We also assess the effect of bedrock depth on soil amplification for a generic soil profile in artificial fill, using both linear and equivalent-linear site response models. Finally, we assess the accuracy of the model results by comparing the predicted (linear site response) and observed site response at the Northeastern University (NEU) vertical seismometer array during the 2011M 5.8 Mineral, Virginia, earthquake. Site response at the NEU vertical array results in amplification on the order of 10 times at a period between 0.7–0.8s. The results from this study provide evidence that the mean short-period and mean intermediate-period amplification used in design codes (i.e., from the Fa and Fv site coefficients) may underpredict soil amplification in strong impedance contrast environments such as Boston.