Vertical Ground Acceleration Research Articles

Relationship Between Vertical Ground Reaction Force and Acceleration from Wearable Inertial Measurement Units During Single-Leg Drop Landing After Anterior Cruciate Ligament Reconstruction

The purpose of this study was to clarify the relationship between vertical ground reaction force (VGRF) and acceleration from wearable inertial measurement units (IMUs) during single-leg drop landing after anterior cruciate ligament reconstruction (ACLR). Twenty-six participants, 42.4 ± 5.3 weeks after ACLR, performed three single-leg drop landing trials bilaterally. The peak VGRF was assessed using a force plate. The resultant acceleration was calculated using IMUs attached to the shank, thigh, and lumbar region. Univariate regression analysis was performed to examine the linear relationship between the VGRF and resultant acceleration. The limb symmetry index (LSI) of the VGRF was linearly associated with the LSI of the resultant accelerations at the shank, thigh, and lumbar sensors (R2 = 0.166, p = 0.039; R2 = 0.525, p < 0.001; and R2 = 0.250, p = 0.009, respectively). In the involved limb, only the resultant acceleration at the thigh was a significant predictor of VGRF (R2 = 0.490, p < 0.001), whereas in the uninvolved limb, the resultant accelerations at the shank, thigh, and lumbar sensors were significant predictors of VGRF (R2 = 0.245, p = 0.010; R2 = 0.684, p < 0.001; and R2 = 0.412, p < 0.001, respectively). Caution may be required when using IMUs to predict VGRF asymmetry because the coefficient of determination for predicting VGRF is lower in the involved limb than in the uninvolved limb.

A FRCM technique for strengthening of masonry domes against near-fault pulse-like vertical excitations

Masonry domes have been used extensively in historic architecture, covering large interior spaces in structures ranging from temples, mausoleums, palaces and fortresses to baths, churches, and mosques. This research is motivated by the post-earthquake observations following the 2023 Kahramanmaraş earthquakes, which revealed significant structural damage to masonry domes caused by near-fault pulse-like horizontal and vertical ground motions. Previous studies in the literature have not investigated the impact of near-fault pulse-like vertical and horizontal ground motions on the seismic performance of masonry domes. This paper aims to explore the impact of the vertical component on the seismic damage behavior of masonry domes subjected to near-fault pulse-like ground motions. Additionally, it seeks to propose a cost-effective seismic strengthening technique characterized by minimal intervention, improved workability, and reduced cost. A 3D finite element model of a masonry dome with a drum was created using the isotropic continuum macro modeling technique with homogenized properties. The Concrete Damage Plasticity (CDP) model was selected as the nonlinear material model. Near-fault pulse-like vertical and horizontal ground motions recorded during the February 6, 2023, Kahramanmaraş earthquake (M7.7) were chosen for the nonlinear analysis. Initially, displacements, tensile strains, and damage patterns of masonry domes subjected to near-fault pulse-like vertical and horizontal ground motions were obtained and thoroughly evaluated for V/H (the peak vertical ground acceleration to the peak horizontal ground acceleration ratio) ratios of 0.0, 0.50, 0.75, 1.0, and 1.25. Subsequently, seismic analyses were conducted on masonry domes strengthened with four different Fabric Reinforced Cementitious Mortar (FRCM) configurations under near-fault pulse-like excitations with a V/H ratio of 1.25 to propose an optimal strengthening technique.

Peak Acceleration Distribution on the Surface of Reef Islands under the Action of Vertical Ground Motion

This paper adopts the fluid–structure coupling algorithm based on the acoustic fluid element, the fluid dynamic artificial boundary, and the consistent viscoelastic artificial boundary of solid media to establish a finite element model of the dynamic interaction of the reef-island–seawater system. Then, a numerical simulation of the seismic response of the reef-island site is carried out to study the seismic ground motion distribution patterns of the reef–seawater site and the reef-island–lagoon site. The innovation of this article is that the influence of reef–island topography and fluid–structure coupling is considered in the analysis when vertical ground motion is input. The results show that the slope angle of the bottom layer has a significant influence on the peak ground acceleration distribution and peak size on the island slope surface and the reef platform. For high-frequency input motion, a smaller reef platform width will induce a larger peak acceleration response on the reef platform. Seawater has a significant suppressive effect on vertical ground acceleration. The more high-frequency components of the input bedrock motion, the more obvious this suppression effect will be. The existence of the lagoon will amplify the maximum peak acceleration on the reef platform. According to the calculation results, lagoon terrain can amplify the maximum horizontal and vertical peak accelerations on the reef platform by about 19 and 6 times relative to the free-field results, respectively.

Seismic design and performance analysis of perforated rubber buffer layer in tunnel

Tunnels may be damaged under earthquakes, which has been observed by many earthquake events, and the buffer layer is proposed and widely investigated as a damping measure. The rubber is considered as a qualified buffer layer material because of its small elastic modulus and super elasticity, but its high price makes it difficult to apply in practical engineering. Therefore, four types of rubber buffer layers are proposed in this study, including the common rubber buffer layer and three types of perforated rubber buffer layers (PRBL), which can reduce the seismic damage and cost of tunnels. A pseudo-static method for calculating the seismic response of tunnels under horizontal and vertical earthquake motions is proposed and verified. Based on proposed pseudo-static method, a seismic design method for the buffer layer is present, and the proposed seismic design process is used to study the seismic mitigation performance of buffer layers. The initial design of the buffer layer under earthquake action E1 is carried out by pseudo-static method, and then the seismic mitigation performance is verified through dynamic time history analysis method under earthquake action E2. The earthquake action E1 and earthquake action E2 are the earthquake actions with short and long return periods of the engineering site, respectively. The results show that the common rubber buffer layer has almost no seismic mitigation performance, and the three types of PRBLs have good seismic mitigation performance. The type IV buffer layer is strip-shaped PRBL and the holes are along the longitudinal direction of the tunnel, and it has optimal seismic mitigation performance. The effects of vertical earthquake motion and peak ground acceleration (PGA) on the seismic mitigation performance of the buffer layer are studied. The results show that vertical earthquake motion has little effect on the seismic mitigation performance of different types of buffer layers. For different PGAs, the type IV buffer layer is able to efficiently decrease the peak internal force of secondary lining. The results also prove the validity of design method.

Observed nonlinear site amplification of vertical ground motion in Taiwan

The objective of this study is to evaluate the possible reason for the observed nonlinear site amplification (NSA) of vertical ground motions in Taiwan. First, we observe that NSA generally occurs simultaneously in both the horizontal and vertical components of a ground-motion record and that the NSA levels are similar between these components. We also observe that most vertical peak ground acceleration (PGA) and vertical peak oscillator spectral acceleration (SA) responses for different periods occur during the shear wave (S-wave) window after S-wave arrival. The differences in the source, path, and site effects on PGA and SA responses occurring during the pressure wave (P-wave) and S-wave windows are evaluated individually through a regression analysis. We determine that NSA is observed only when PGA and SA responses occur during the S-wave window. This evidence demonstrates that the observed NSA of vertical ground motions in Taiwan may result from the hysteresis of the soil layer subjected to S-waves. This study provides physical evidence for the observed NSA of vertical ground motions in Taiwan.

Experimental verification and performance evaluation of an inertia-type bidirectional isolation system

Both horizontal and vertical ground motion can cause damage to vibration-sensitive equipment. However, most mature seismic isolation devices only isolate horizontal ground acceleration; few devices isolate both vertical and horizontal ground acceleration. In this paper, a novel inertia-type bidirectional isolation system (IBIS) is proposed that comprises independent vertical and horizontal seismic isolators. The IBIS’s vertical isolator comprises leverage apparatus with a counterweight, which provides a vertical lifting force in the static state to balance the self-weight of the isolated object, and an additional inertial force in the dynamic state, resulting in higher static but lower dynamic effective vertical stiffness. The horizontal isolator is a conventional sliding-type system comprising a sliding platform and pair of springs. The IBIS’s equations of motion are derived by using Lagrange’s equation, and the theoretical model is verified through shaking-table test results. Numerical simulation and experimental results show that the IBIS has an anti-resonance property in the vertical direction, leading to higher isolation performance under both near-fault and far-field ground acceleration. The conventional sliding-type horizontal isolator component performs well under far-field ground acceleration but may perform unsatisfactorily under near-fault ground acceleration.

Vertical floor acceleration spectra for regular steel frame structures

The scope of this contribution is the assessment of the vertical peak component acceleration of single-degree-of-freedom (SDOF) oscillators attached to elastic moment-resisting steel frames subjected to recorded ground motions. These SDOF oscillators represent nonstructural components (NSCs) flexibly attached to the load-bearing structure whose acceleration demands correlate with their maximum strength demands. The results in terms of floor acceleration spectra show that the interaction between a vertically oscillating NSC and the structure is much more pronounced than for horizontally oscillating NSC of the same mass and natural frequency. This means that even for vertical NSCs with very small mass (in the case of the investigated eight-story frame 0.01% of the frame mass depending on the number of stories) a coupled analysis is required for a realistic prediction of the NSC acceleration demand. In a parametric study of vertical NSCs attached to steel frame structures of different number of stories, a median vertical peak component acceleration was observed up to 5.5 times larger than the vertical peak floor acceleration of the attachment node of the load-bearing structure and up to 20 times larger than the vertical peak ground acceleration. The amplification of the vertical acceleration response is thus of the same order of magnitude as for horizontal NSCs. This means that the vertical dynamic response of flexible NSCs cannot be neglected and should therefore be studied in more detail in the future.

Vertical floor spectra in low- and mid-rise elastic RC moment resisting frame buildings

To examine how floor spectral accelerations affect the design force of flexible Non-Structural Components (NSCs), the present study discusses the estimation of floor response spectra resulting from strong vertical seismic motion. 3-, 6-, 9- and 12-storey reinforced concrete buildings with moderately ductile moment-resisting frame systems, designed in accordance with the National Building Code of Canada [25] were selected for this research. 65 sets of historical records relating to 31 severe earthquakes from across the world were used to analyze the linear behavior of these structures. A constant amplification of the Vertical Floor Spectral Acceleration (FSAV) was observed along the building height. This amplification was noticeably elevated for slab nodes, especially at the center of the interior slab and in shorter buildings. Furthermore, the vertical component of the earthquake had a greater impact at shorter periods, since the maximum vertical acceleration occurred at periods lasting less than 0.35 sec. Finally, equations to estimate FSAV corresponding to the input vertical ground acceleration were proposed for typical code-conforming RC frame buildings.

Vertical effects of near-fault ground motions and the optimal IMs for seismic response of continuous girder bridges with FPB isolators

The characteristics of vertical components in the near-fault region were investigated based on 121 pairs of typical near-fault ground motions. A weak positive correlation between the vertical and horizontal peak ground acceleration (PGA) and peak ground velocity (PGV) is shown. Basically, the ratios of vertical to horizontal peak ground acceleration and velocity of the near-fault ground motions comply with the lognormal distribution, and the vertical ground motions are significantly stronger at lower periods. Fifteen scaler horizontal and nine scaler vertical IMs are compared to select the optimal scaler IMs of horizontal and vertical seismic demands of an isolated girder bridge with friction pendulum bearings (FPB isolators). It is found that acceleration-related scalar IMs perform better for vertical seismic demands, while velocity-related scaler IMs perform better for horizontal seismic demands. The optimal vector-valued IM, consisting of scalar horizontal and vertical IMs in the forms of IMh,IMv, for horizontal seismic demands were proposed. The optimal vector-valued IMs show an apparent improvement in efficiency compared with the corresponding scaler IMs when vertical components are considered. Furthermore, the probabilistic seismic demand models (PSDMs) for horizontal seismic demands with optimal vector-valued IM were adopted to assess the seismic demands under a given intensity of vertical and horizontal ground motions. It is identified that the vertical effects significantly influence the shear force of piers while slightly influencing the curvature of piers and bearing displacements.

Моделирование сейсмического воздействия на земляное полотно с демпфирующим слоем. Сравнение аналитического и конечно-элементного методов

The mathematical modeling of seismic impact on the railway subgrade has been considered. While modeling used the coefficients of horizontal and vertical ground accelerations, regulated by building codes, and the generated accelerogram. Analyzing the stability and stress-strain state of the subgrade during an earthquake reduires calculations carried out in the GEO5 «Slope Stability» and GEO5 FEM software packages. The convergence of the results has been assessed. The most unfavorable combination of directions of seismic impact components has been determined, and a conclusion has been made about their influence on the calculation results. The values of the stability coefficient for the embankment, the magnitude of stresses and deformations in the structure of the subgrade and foundation have been given for various parameters of the design scheme and for different earthquake intensities. The results of the analysis allow to estimate the correctness of the reflection of the picture of the stress-strain state of the embankment has been assessed. The necessity and effectiveness of using the finite element method for calculating the stress-strain state of a soil structure taking into account seismic effects is substantiated. The nature of the influence of the physical and mechanical characteristics of the roadbed structure on its stability and stress-strain state during an earthquake has been determined. The author made some calculations of a structure with a damping layer introduced into the structure to reduce the negative impact of seismicity. The dependences of the stability coefficient, stresses and deformations in the roadbed on damping parameters have been determined. The possibility of increasing stability, reducing stresses and reducing deformations of the subgrade under seismic influences using a damping layer or using soil with certain physical and mechanical characteristics as a material for embankment has been established.

Orthotropic plates with dynamic vertical seismic load modeled as multi line

Calculation plate floor concrete, using a static load which is a gravity load consisting of a live load and a dead load, with various of boundary conditions, floor slabs are orthotropic plate, and rarely account for dynamic loads due to vertical seismic loads, with other boundary conditions, such as Clamped, simply supported, ES (Elastic Support), ER (Elastic Restraint), and ESR (Elastic Support and Restraint). Analytical solution based on the Modified Bolotin Method to analyze floor slab under Vertical Peak Ground Acceleration (PGAv), the natural frequency solution based on auxiliary Levy’s type problems. Dynamic vertical seismic loads using multiline, first line at 0 < t < 0.5 is linear equation, second line at 0.05 < t < 0.15 is quadratic equation, third line 0.15 > t < 0.6 is sextic equation, last line, t > 0.6 is linear equation, vertical seismic load with two conditions far fault and near fault, multi-line equation are depending on (PGAv/g). A numerical example is given, for various boundary conditions, and far fault, translational stiffness (kx, ky) and rotational stiffness (cx ,cy), from the results of plate calculations due to dynamic vertical seismic loads with 5 types of edge support, ES (elastic support) is the best result.

Inversion of acoustic thunder source spectral model from thunder-induced seismic waves in megacity

SUMMARYThunder-induced seismic waves recorded at dense seismic stations in Seoul, South Korea are analysed for inversion of thunder source spectra. Thunder-induced seismic waves from four local thunder events are analysed. A theory is introduced for the inversion of acoustic source spectra from thunder-induced seismic waves. In the course of source-spectral inversion, the propagation and acoustic-to-seismic coupling effects are counted. The thunder-induced seismic signals were well identified at distances of <∼20 km. Direct acoustic-to-seismic coupled seismic waves present apparent phase velocities of sound speed in atmosphere (340 m s−1). Thunder-induced seismic waves are dominant at high frequencies (>20 Hz). Vertical peak ground accelerations of thunder-induced seismic waves in local regions (0.024–0.110 m s−2 at distances of 2.4–3.7 km) are equivalent to the ground motion levels induced by a moderate-size (∼M5) earthquake at regional distances. The thunder-induced acoustic waves in the atmosphere are obtained by removing the acoustic-to-seismic coupling effect and site-response effect from the observed thunder-induced seismic waves. The quality factors for acoustic wave attenuation in the atmosphere are determined. Urban landscapes and atmospheric effects cause strong acoustic attenuation over atmospheric absorption. Acoustic thunder source spectra are determined by stacking the inverted acoustic spectra at all stations. The peak frequencies of acoustic thunder source spectra are around 34–36 Hz, suggesting the acoustic energy per unit length in lightning strikes to be ∼4 × 106 J m−1. Local seismic records are applicable for the investigation of thunder and lightning properties.

Monitoring the 2021 Mw 8.2 Alaska Earthquake by an Offshore Seismic and Fluid Pressure Observation Network and Implications for Ocean‐Crust Dynamic Coupling

AbstractGround shaking caused by earthquakes is accompanied by seafloor and sub‐seafloor formation fluid pressure variations in offshore areas, but there have been few collocated observations of these signals. In this work, we report seismic and high‐sampling‐rate fluid pressure records of the 2021 Mw 8.2 Alaska earthquake by the Ocean Networks Canada (ONC) NEPTUNE observatory at an epicentral distance of ∼2,200 km in the northeast Pacific Ocean. The system comprises observatory nodes in various tectonic environments, with each node including buried broadband seismometers, seafloor pressure sensors, and, at two nodes, borehole pressure sensors. Seismic and tsunami waveforms of the Mw 8.2 earthquake were documented in detail. Seismic seafloor pressure variations (Psf) were dominated by Rayleigh waves of periods between 5 and 50 s, with peak amplitudes of 3–4 kPa at most sites. Waveform similarity and the linear scaling between Psf and vertical ground acceleration indicate forced acceleration of the water column being dominant in governing Psf during long‐period surface‐wave arrivals, with an additional component of elastic oscillation occurring at higher frequencies (>0.1 Hz) causing extra pressure signals. Analysis of formation pressure variations due to various types of ocean loading of distinctly different frequencies (e.g., tides, tsunami, and infragravity waves) shows stable one‐dimensional vertical loading efficiencies that depend on lithology at each borehole site, with loading response being strongly influenced by the presence of free gas at shallow depths within the Cascadia accretionary prism. Inter‐site comparisons of seismic and seafloor pressure waveforms demonstrate a key role of sediment thickness in the amplification of surface wave amplitudes.

Effect of simulation accuracy of shear keys shear state on seismic response of friction pendulum bearing

In order to study the effect of simulation accuracy of shear keys shear state on seismic response of friction pendulum bearing, a vertical spring-friction system composed of equivalent components is used to simulate the friction pendulum bearing effectively, and two numerical calculation programs are developed. A spring element with life-and-death characteristics is used to realize the simplified simulation of shear keys shear state in the program 1, while shear keys on both sides of the friction pendulum bearing in the same direction are considered independently in the program 2. By comparing the seismic responses of the two programs with different shear key shearing force, vertical spring stiffness and different peak ground acceleration (PGA) conditions, it can be concluded that the precise simulation of shear keys shear state can more accurately calculate the shear key shear time and the maximum acceleration of the structure, which is beneficial to seismic isolation design. When the shear key shearing force is large and the PGA is small, the relative displacement response of bearing will be small if the shear keys are simultaneously sheared off. Increasing the stiffness of the vertical spring can reduce the residual displacement of the friction pendulum bearing. The simulation accuracy of shear key shear state has little influence on the relative displacement response when the equivalent stiffness of friction pendulum bearing is large. In this case, the shear key shear state can be simplified.

PREDICTION MODEL FOR BASE SHEAR INCREASE DUE TO VERTICAL GROUND MOTION IN FRICTION PENDULUM ISOLATED STRUCTURES

Seismic isolation is one of the most effective seismic hazard mitigation techniques, which has been implemented in many structures. Friction pendulum isolators are one of the most popular isolation devices to achieve energy dissipation and shear resistance that depends on the effective radius and instantaneous vertical force on them. So, the horizontal response of this type of isolators is coupled with the axial load on them, which could change due to vertical acceleration during ground shaking. Thus, it makes consideration of the vertical excitation in the design and analysis phase inevitable, especially for structures in those regions where vertical ground accelerations are more pronounced. In this study a model for the prediction of increase in base shear due to vertical motion for friction pendulum isolated structures is proposed. A simple single friction pendulum isolator system is utilized with the assumption of rigid superstructure on top and subjected to a hundred earthquake ground motions with different characteristics. A multi-layer perceptron model with three layers is utilized, and a simple computer program, which is open-source, is prepared to construct probability curves. With the help of the program, within the range of the considered structural parameters in the study, probability curves related to increase in base shear, maximum isolator displacement and residual isolator displacement can be constructed, and designers can have a rough estimation on modification of these parameters due to vertical ground motion.

Effects of vertical ground acceleration on the seismic moment demand of bridge superstructure connections

Vertical ground accelerations are not always considered in bridge design practice, which is partially due to the lack of consistent recommendations in the design codes and standards. However, undeniably, the vertical ground acceleration component in an earthquake can be large. While the effects of vertical ground acceleration on bridges have been studied in the past, the focus has mostly been on performance of the substructure, especially columns. This study thus investigates the effects of large magnitude of vertical ground accelerations on the response of bridge superstructures as it can experience significant impact, particularly in the connections and bearing forces. To quantify the effects of vertical ground accelerations and compare the outcomes with existing design recommendations, an analytical study is undertaken on the seismic response of straight, skewed, and curved steel bridge superstructures with drop pier caps. The results show that the vertical accelerations can amplify the superstructure moment demands at the midspan and support locations by as much as above 100%. It is further shown that the current design practice to account for vertical ground acceleration effect is not sufficient for earthquakes with high vertical ground accelerations. Although the superstructure used in this study incorporated steel girders, the results are also applicable to bridges with concrete superstructure.

Characterization of ground oscillations induced by underground mining

We examine ground acceleration during M1.5 and M2.0 seismic events induced by underground mining at Upper Silesian coal basin and Legnica Glogow copper mine, respectively, using methods of nonlinear time series analysis, in order to confirm its stochastic nature. Recorded time series are firstly embedded into the adequate phase space using the mutual information and box-assisted methods. After this, we performed stationarity test, by which we confirmed that the examined ground acceleration belongs to a group of stationary processes. Surrogate data testing is applied then, which resulted in following: (1) horizontal ground acceleration at Legnica Glogow copper mine represents stationary linear stochastic processes with Gaussian inputs, (2) ground acceleration at Upper Silesian coal basin originates from a stationary Gaussian linear process that has been distorted by a monotonic, instantaneous, time-independent non-linear function, (3) vertical ground acceleration at Legnica Glogow copper mine could not be ascribed to any of the examined processes, probably due to high level of instrumental or background noise. Low values of determinism coefficient (c≤0.7), negative values of maximum Lyapunov exponent and quick saturation of neighboring points distance with the increase of embedding dimension indicate the absence of determinism in the observed ground acceleration time series.

Analytical approach for vertical floor acceleration of regular RC frames under earthquake excitation

Vertical floor acceleration (VFA) analysis arises as an important issue for seismic design of floor-attached nonstructural components (e.g., ceilings). However, to date, estimating the VFA is hardly accessible in the literature. In this paper, an analytical method is proposed for the VFA of regular RC frames. Here “regular” means the frame has uniform spans along each principal direction, so the structure can be represented by a single-span analogy. Firstly, the fundamental frequency, modal mass, and modal participation factor of a clamped floor slab are analyzed based on the classic thin-plate theory. Then, the dynamic properties of the clamped floor slab are adjusted to account for the effect of the flexible beam restraints (non-clamped). According to the adjusted dynamic parameters, the beam-restrained slab is substituted by a single-degree-of-freedom system, and is assembled with the column-beam system to form the global dynamic model for the structure. Based on the assembled model, the analytical process for the VFA is presented. The feasibility of the model is validated using the finite element modelling (FEM) method. The vertical dynamic properties and the peak VFA of a single-, 3-, 6-, and 9-story frame are computed using the FEM and the proposed analytical approach. Results show that the VFA obtained from the analytical approach is close to the FEM outcomes. Furthermore, important features of VFA are revealed by the computation. It is shown that the VFA could be 10 times as large as the peak vertical ground acceleration. A larger VFA appears at the higher stories, yet the relationship between the VFA and the height is nonlinear because of the effects of the higher-order modes.

Attenuation Relationships for Horizontal and Vertical Peak and Spectral Accelerations for Alborz Zone of Iran

ABSTRACT In the present study, the attenuation relationships of horizontal and vertical peak ground acceleration and 5%-damped spectral acceleration, suitable for the northern region of Iran (Alborz Zone), are presented. The dataset contains 308 three-component records from 104 events with moment magnitudes between 4.5 and 7.6 and hypocentral distances from 10 to 200 km. Site conditions of the stations have been classified into two categories, rock and soil. To determine the unknown constants of the relations, one-step nonlinear regression analysis was used. Finally, it was found that the proposed attenuation relationships show good compatibility with a number of past well-known studies.

Smooth Crustal Velocity Models Cause a Depletion of High-Frequency Ground Motions on Soil in 2D Dynamic Rupture Simulations

ABSTRACTA depletion of high-frequency ground motions on soil sites has been observed in recent large earthquakes and is often attributed to a nonlinear soil response. Here, I show that the reduced amplitudes of high-frequency horizontal-to-vertical spectral ratios (HVSRs) on soil can also be caused by a smooth crustal velocity model with low shear-wave velocities underneath soil sites. I calculate near-fault ground motions using both 2D dynamic rupture simulations and point-source models for both rock and soil sites. The 1D velocity models used in the simulations are derived from empirical relationships between seismic wave velocities and depths in northern California. The simulations for soil sites feature lower shear-wave velocities and thus larger Poisson’s ratios at shallow depths than those for rock sites. The lower shear-wave velocities cause slower shallow rupture and smaller shallow slip, but both soil and rock simulations have similar rupture speeds and slip for the rest of the fault. However, the simulated near-fault ground motions on soil and rock sites have distinct features. Compared to ground motions on rock, horizontal ground acceleration on soil is only amplified at low frequencies, whereas vertical ground acceleration is deamplified for the whole frequency range. Thus, the HVSRs on soil exhibit a depletion of high-frequency energy. The comparison between smooth and layered velocity models demonstrates that the smoothness of the velocity model plays a critical role in the contrasting behaviors of HVSRs on soil and rock for different rupture styles and velocity profiles. The results reveal the significant role of shallow crustal velocity structure in the generation of high-frequency ground motions on soil sites.