Amplification Of Seismic Waves Research Articles

Seismic Wave Amplification Characteristics in Slope Sections of Various Inclined Model Grounds

The collapse of slopes caused by earthquakes can lead to landslides, resulting in significant damage to both lives and structures. Seismic reinforcement of these slopes can protect social systems during an earthquake. In South Korea, where more than 70% of the land is mountainous, the stability of slopes is of paramount importance compared to other countries. While many seismic designs are based on peak ground acceleration (PGA), there is relatively little consideration given to the extent of PGA’s influence, and few studies have been done. This study aims to assess the seismic amplification of slopes with multilayers using a 1 g shaking table and verify the results through numerical analysis after confirming the impact of PGA at specific points. Typically, slope model experiments are conducted on single-layered ground models. However, actual ground conditions consist of multiple layers rather than a single layer, so a multi-layered model was created with different properties for the upper and lower layers. Two multi-layered ground models consisting of two layers were created, one with a flat ground surface and the other with a sloped surface. The properties of the two layers in each model were configured as a single layer to create the slope models. The peak ground acceleration (PGA) of the four ground models was compared, revealing that seismic wave amplification increases as it moves upward, and the amplification is even greater when transitioning from the lower to the upper ground layers, leading to different dynamic behavior of the slope. Through the contour lines, the influence of PGA was further confirmed, and it was found that approximately 60% of the PGA impact occurs at the topmost part of the slope on average. Analysis of the earthquake waves showed that the top of the slope experienced an average amplification of about 31.75% compared to the input motion, while the lower part experienced an average amplification of about 27.85%. Numerical analysis was performed using the ABAQUS program, and the results were compared with the 1 g shaking table experiments through spectral acceleration (SA), showing good agreement with the experimental results.

Nonlinear Seismic Response of Tunnel Structures under Traveling Wave Excitation

Tunnels traditionally regarded as resilient to seismic events have recently garnered significant attention from engineers owing to a rise in incidents of seismic damage. In this paper, the reflection characteristics of the elastic plane wave incident on the free surface are analyzed, and the matrix analysis method SWIM (Seismic Wave Input Method) for the calculation of equivalent nodal loads with artificial truncated boundary conditions for seismic wave oblique incidence is established by using coordinate transformation technology, according to the displacement velocity and stress characteristics of a plane wave. The results show that the oblique incidence method is more effective in reflecting the traveling wave effect, and the “rotational effect” induced by oblique incidence must be considered for P wave and SV wave incidence, including the associated stress and deformation. This effect exhibits markedly distinct rotational phenomenon. In particular, the P wave incidence should be focused on the vault and the inverted arch due to the expansion wave. With the increase of the oblique incidence angle, the structural stress and deformation are rotated to a certain extent, and the values are significantly increased. Simultaneously, the shear action of the SV wave may result in “ovaling” of the tunnel structure, thereby facilitating damage to the arch shoulder and the sidewall components. As the oblique incidence angle, the potentially damaging effects of the “rotational effect” to the vault and the inverted arch, but the numerical value does not change significantly. In addition, in comparison to a circular cross-section, the low-frequency amplification of seismic waves in the surrounding rock and the difference of frequency response function in different parts of the lining are more pronounced. In particular, the dominant frequency characteristics are significant at P wave incidence and the seismic wave signal attenuation tends to be obvious with increasing incidence angle. In contrast, SV waves exhibit more uniform characteristics.

Nationwide frequency-dependent seismic site amplification models for Iceland

Seismic wave amplification due to localized site conditions or site-effects, is an important aspect of regional seismic hazard assessment. In the absence of systematic studies of frequency-dependent site-effects during strong Icelandic earthquakes, various local site proxies of large-scale studies in other seismic regions have been used and/or proposed for application in Iceland. Recently, however, earthquake site-effects were rigorously quantified for 34 strong-motion stations in Southwest Iceland for the first time and correlated to distinct Icelandic geological units of hard rock, rock, lava rock, and sedimentary soil. These units are prevalent throughout Iceland and in this study therefore, we present 1) nationwide maps of proxies (e.g. slope, Vs30, geological units) that may contribute to a better estimation of site effects and associated, 2) frequency-dependent site-amplification maps of Iceland relative to the median ground-motion prediction of Rahpeyma et al. (2023) [55]. We particularly focus on the two transform zones of the country, on the basis of digital elevation models and detailed geological maps. Specifically, the frequency-dependent site factors for each geological unit are presented at 1, 2, 5, 7, 10–30 Hz, and PGA. Finally, for comparison, we generate site amplification maps based on recent large-scale models developed in other seismic regions and/or applied in other studies (e.g., ESRM20) as well as various site proxies they are based on (e.g., geology- and slope-based inferred VS30, geomorphological sedimentary thickness). We compare site-proxy maps and amplification maps from both Icelandic and large-scale, non-Icelandic, models. Specifically, neither spatial patterns nor amplification levels in either proxy or amplification maps from large-scale non-Icelandic studies resemble those observed from local quantitative strong-motion research as presented in this study. We attribute the discrepancy primarily to the young geology of Iceland and its formation history. Additionally, this study compares model performance across frequencies by assessing the bias of model predictions against empirical site amplifications in the South Iceland Seismic Zone, accounting for site-to-site variability of residuals indicating the superior performance of the local amplification model. The results presented in this study now allow a more informed estimation of earthquake ground motion amplitudes on various geological units that are expected to result in more reliable and information-based seismic hazard estimates in Iceland.

Seismic wave amplification in a weakly nonlinear two-layered soil deposit

Based on numerous observations, local soil site conditions can significantly affect the formation of seismic responses. In this paper, we examine seismic responses caused by shear waves propagating through a two-layered soil deposit. The aim of the research is to study the phenomenon of amplification of shear waves due to the resonant properties of the soil deposit and the nonlinear characteristics of partial layers, which are assumed to be the cubically nonlinear continuous media. The target problem relates to a nonlinear boundary value problem, the solution of which is carried out using a semi-analytical approach. According to the approach, the problem’s solution is sought using the method of separation of variables, while the solution to the corresponding spectral problem is derived in the form of a power series. Additionally, good agreement is shown between theoretical studies and numerical simulations. The developed approach allows one to evaluate the amplification factor for a nonlinear two-layered soil deposit and to detect changes in the shape of amplification factor profiles when the frequency of an incident wave on a rigid bedrock is varied.

Prediction of Fourier Amplitude Spectrum of Ground Motion in Mexico City from Subduction Thrust Earthquakes

Mexico City, one of the largest cities in the world, experiences frequent, devastating interplate earthquakes that originate on the subduction thrust along the Pacific coast of Mexico more than 250 km away. A notorious example is the 19 September 1985 Michoacán earthquake (Mw 8.0) which killed ~ 10,000 persons and caused wide-spread destruction in the city. The main cause of seismic damage in Mexico City is its subsoil that amplifies the ground motion. In view of the seismic hazard faced by the city, a reliable estimation of ground motion during future earthquakes is of vital importance. We present a new ground motion prediction equation (GMPE) for the Fourier amplitude acceleration spectrum (FAS) from subduction thrust earthquakes along the Pacific coast of Mexico at the reference station, CU, located in the firm zone of Mexico City. The GMPE is derived via Bayesian regression analysis and is based on an enlarged set of recordings (1965-2020; 40 earthquakes; 250 ≤ R≤ 500 km; 5 ≤ Mw ≤ 8.0). An important feature of the new GMPE is that it includes a term to model different attenuation along different ray paths. The inclusion of this term leads to a reduction in the aleatory variability of the GMPE, particularly at high frequencies. Since spectral amplification of seismic waves with respect to CU is known at many sites in the city, the FAS at these sites can be computed if it is known at CU. The new GMPE has been incorporated in a fully Fourier-based probabilistic seismic hazard analysis of Mexico City.

Mexico City Earthquake of 11 May 2023 (Mw3.2)

On 11 May 2023 a local earthquake in Mexico City was felt very strongly in Mixcoac, San Angel, and Coyoacán. The event was part of a seismic sequence that had begun about 6 months earlier. Peak Ground Acceleration (PGA) at the closest station (distance ~ 1 km), located in the hill zone, was ~ 0.18 g. Although the response spectrum at short periods at this station exceeded the design spectrum specified in the Mexico City´s Building Code, no structural damage was reported. Moment tensor inversion of bandpass filtered (0.08 – 0.24 Hz) displacement records yields M0 = 6.8x1013 N-m (Mw 3.2), H = 0.7 km, and the likely fault plane characterized by φ = 2700, δ = 760,On 11 May 2023 a local earthquake in Mexico City was felt very strongly in Mixcoac, San Angel, and Coyoacán. The event was part of a seismic sequence that had begun about 6 months earlier. Peak Ground Acceleration (PGA) at the closest station (distance ~ 1 km), located in the hill zone, was ~ 0.18 g. Although the response spectrum at short periods at this station exceeded the design spectrum specified in the Mexico City´s Building Code, no structural damage was reported. Moment tensor inversion of bandpass filtered (0.08 – 0.24 Hz) displacement records yields M0 = 6.8×1013 N-m (Mw 3.2), H = 0.7 km, and the likely fault plane characterized by φ = 2700, δ = 760, λ = -750. These source characteristics are very similar to those estimated for the 17 July 2019 earthquake which occurred during a swarm-like seismic activity about 5 km to the north. Spectral analysis of recordings at 19 sites in the hill zone, 14 in the transition zone, and 41 in the lake-bed zone reveals great variability of the ground motion within each of the zones. Estimated stress drop, Δσ, is 0.5 MPa. A large disparity is found between the observed source spectrum and theoretical source spectrum; their ratio provides an estimation of the amplification of seismic waves as they travel through the layers of decreasing velocity at shallower depth. We denote this ratio as the site effect. Predicted PGA and PGV for an Mw 3.2 earthquake, computed using stochastic technique (Boore 1983, 2003), assuming a Brune ω-2 source, Δσ = 0.5 MPa and including the site effect, are in reasonable agreement with the observations. Expected PGA and PGV at the epicenter of a postulated Mw 5 earthquake are 0.6 g and 60 cm/s at a generic hill-zone site; the expected values are twice as large in the lake-bed zone. These predictions should, however, be taken with caution as they are based on several approximations.

Performance evaluation of parameters as estimators of seismic site effects in northern South America

In this study, we investigate the performance of several parameters as estimators of seismic site effects for sites in northern South America. Investigated parameters include the conventional time-averaged shear wave velocity in the upper 30 m (VS30), the predominant period of the site, and horizontal-to-vertical spectral ratios. To assess the performance of these parameters, we estimate the amplification of seismic waves within shallow soil layers (i.e., site effects) at recording stations across northern South America. The site amplification is estimated by analyzing the residuals calculated from ground-motion records with respect to model predictions for hard-rock site conditions. Several functional forms were introduced to express the linear site amplification in terms of the explored parameters. We evaluate the efficacy of the parameters, as well as their advantages and limitations, by considering their impact in the site-to-site standard deviation of the residuals between observations and predictions using the introduced functional forms.

Three-dimensional broadband simulation of near-fault seismic ground motion considering complete source-path-site effect: Modeled by fast multipole indirect boundary element method

Efficient and accurate numerical methods are essential for analyzing seismic wave propagation and amplification in near-fault complex sites. Understanding the complete process of ground motion simulation, including fault rupture, path propagation, and near-surface complex site response, is crucial for studying earthquake damage mechanisms, seismic zoning, and designing large-scale engineering structures. In this study, we propose a fast multipole indirect boundary element method (FMIBEM) to achieve broadband and high-efficiency simulation, enabling a comprehensive analysis of the complete process involving seismic ground motion. The FMIBEM significantly reduces the computational and storage costs associated with 3D near-fault complex site seismic wave scattering problems to O(N). We validate the accuracy of the method by comparing it with the analytical solution. Compared to the conventional indirect boundary element method (IBEM), our proposed method reduces computational time by over 95 % and storage costs by nearly 90 %. FMIBEM greatly enhances the efficiency of the boundary element method for simulating seismic wave scattering in near-fault complex sites. To demonstrate the effectiveness of our approach, we apply the FMIBEM method to two typical 3D near-fault complex site examples of seismic wave scattering. The simulation results successfully capture both the local site amplification effect and the characteristic near-fault seismic features, such as the hanging wall effect, permanent displacement effect, and large velocity pulse.

Effects of Local Soil Profiles on Seismic Site Response Analysis

Local soil conditions play a significant role in the intensity variations of seismic waves during earthquakes. These variations can be either amplified or de-amplified depending on the specific soil conditions. This study aimed to assess the impact of different soil profiles on seismic site responses. The study considered four types of site profiles: sand (Sa), clay (Cl), sand overlying clay (SaCl), and clay overlying sand (ClSa) profiles. To simulate the ground motion, we selected seven sets of strong earthquake records from the European Strong-Motion Database. These records were selected according to Eurocode-8 with a peak ground acceleration (PGA) of 0.24 g, site class A using REXEL computer program. The records were then applied to the bedrock at a depth of 30 meters. Subsequently, a series of 1-D equivalent linear (EQL) response analyses were performed using the STRATA. Amplification factors (AFs) and surface acceleration time histories provided quantitative evaluations for our analysis results. The results demonstrated that site profiles with clay overlying bedrock (SaCl and Cl profiles) exhibited higher seismic amplification and peak ground acceleration in comparison to site profiles with sand overlying bedrock (Sa and ClSa profiles). The maximum median AF is calculated from the SaCl site profile, while the minimum median AF was calculated from the ClSa profile. The relative difference between the maximum and the minimum median AFs was about 33.7%. Based on these results, we can conclude that soft local soils have a pronounced effect on the amplification of seismic waves compared to stiff local soils.

Multipath Transfer-Function Correction Method to Predict Site-Specific Amplification at City Scale

Abstract The site-specific amplification of seismic waves is an essential component of local seismic hazard assessment. It can be evaluated from empirical data, but measurements are feasible just in a limited number of locations. Hence, at the city scale, there is a need for the theoretical prediction and interpolation of the amplification. In this article, we introduce a physics-based method to predict the site-specific amplification and duration in a broad frequency range. The method is based on a novel energy-based concept of the multipath propagation of waves in viscoelastic media with random heterogeneities. The amplification is expressed by the surface-outcrop transfer function of the multipath wave propagation, which is defined by expected values of the energy spectral ratio. The method is applied to the near-surface 2D velocity model in the city of Zürich in Switzerland. The predicted amplification is validated by empirical data at a nearby seismic station, and it is compared with the soil class and other site-condition proxies. Finally, the method performance is demonstrated by the prediction of site-specific seismic waveforms and response spectra for the 2022 ML 4.7 Mulhouse earthquake.

Response of Sandy and Clayey Soils to Weak And Strong Seismic Loading

The response of sandy and clayey near-surface soils representing the classes of noncohesive and cohesive soils to seismic loading of various intensities is analyzed from the in situ data —from the records by vertical groups of the Japanese nationwide KiK-net strong motion seismograph network. For the analysis, out of a total of ~800 stations, we selected five stations with near-surface sandy soils and five stations with near-surface clayey soils, most purely represented in the upper layers. Using the method (Pavlenko and Irikura, 2003), we have constructed and analyzed the models of strong ground motion behavior for “sandy” and “clayey” stations, showing the distributions of earthquake-induced stresses and strains in the soil layers. Close estimates of the amplification of seismic waves in sands and clays at weak seismic ground motion and close stress-strain relationships characterizing the behavior of the near-surface soils at moderate seismic ground motion are obtained. The liquefaction of sandy soils under strong shaking (the 2011 Tohoku earthquake with Мw ~ 9.0) is analyzed. The effects of the extended seismic sources (directivity of their radiation pattern) on the behavior of sandy and clayey soils and the amplification of seismic waves in these soils is studied. Differences in the behavior of sandy and clayey soils are noted only at strong seismic motions: liquefaction in sandy soils is possible if the groundwater level is on the order of a few meters from the surface, while in clayey soils there is no liquefaction.

Research on Seismic Wave Delay and Amplification Methods in the Shaking Table Test of Large-Span Structures in Mountain Areas

The traveling wave and slope amplification effects should be considered in the shaking table test of large-span structures in mountain areas. Based on the structural characteristics and site conditions of a large-span structure in a mountain area, this paper designed a high-rise steel frame structure with viscous dampers through finite element analysis to amplify seismic waves with a time delay. Then, the original structure and steel frame models with a similarity ratio of 1/40 were made for shaking table tests. The test results showed that a high-rise steel frame structure with reasonable viscous dampers could delay and amplify seismic waves, and the scaled model of the structure could play the same role in shaking table tests. Meanwhile, by comparing the seismic responses of large-span structural models in mountain areas before and after the amplification of seismic wave delays, it was found that the delay and amplification of seismic waves had little impact on the acceleration response of the structure. In contrast, the seismic wave delay played a dominant role in the change in the structural displacement response.

Investigating the Influence of a Pre-Existing Shear Band on the Seismic Response of Ideal Step-like Slopes Subjected to Weak Motions: Preliminary Results

The assessment of slope susceptibility to seismically-induced displacements receives wide attention in the geotechnical earthquake engineering field, but the alteration of the seismic wave inside the slope and at the ground surface due to the presence of a shear band confining a quiescent landslide body is rarely investigated. This paper describes the preliminary results of the numerical analysis of two step-like FE models, reproducing a gentle slope and steep cutting subjected to weak earthquakes, thus focusing on seismic wave amplification processes only. The results show that the higher the thickness of the weakened zone, the higher the maximum value of the amplification factors predicted at the ground surface. For gentle slopes affected by a landslide body confined by a thick shear band, the highest amplification factors are expected in the longer period range of 0.7–1.1 s, while the highest level of amplification is achieved in the intermediate period interval of 0.4–0.8 s in the case of steep slopes. In addition, the parasitic vertical component of acceleration can be considerably amplified beyond the crest and at the toe of the slope for increasing band thickness, especially in the case of steep topography, for which the effects of the shear band morphology enhance those related to the topographic profile. Finally, the fundamental frequency of the sloping deposit is not particularly affected by the presence of the shear band, while the amplitude of the amplification function at the fundamental frequency is clearly related to its thickness.

Direct estimation ofVS30 using spatial autocorrelation and centreless circular array coefficient curves obtained from microtremor array data

SUMMARYThe average S-wave velocity (VS) in the upper 30 m (VS30) is a proxy for seismic wave amplification. Microtremor array exploration is one of the available methods for site characterization, but the recorded data require complicated processing that can lead to different estimations of VS30 depending on the analyst and processing software. We propose a method of estimating VS30 by using derivatives obtained in the early stages of microtremor array data processing. Statistical analysis with 2376 virtually generated subsurface VS structure models revealed that the frequencies at which the spatial-autocorrelation (SPAC) coefficients and centreless circular array (CCA) coefficients take specific values strongly correlate with VS30, which we used to develop formulas for estimating VS30. Numerical validations using actual VS profiles at 616 sites in Japan showed that the proposed method could estimate VS30 with a root-mean-square deviation (RMSD) of 57–80 m/s with SPAC coefficients and 56m/s with CCA coefficients. Our proposed methods were applicable for 98–100 per cent of theVS profiles when we limited our estimation to sites with VS30 < 760 m/s. The results indicated that SPAC coefficients from arrays with radii of 8–20 m can be used for VS30 estimation and are less affected by incoherent noise. In contrast, CCA coefficients are much more sensitive to incoherent noise, which resulted in the overestimation of VS30. The estimated VS30 values from the recorded microtremor array data were in good agreement with the reference values from the actual VS profiles. The proposed method allows for robust and efficient VS30 estimation without relying on the analyst’s skills or software.

Seismic wave amplification characteristics of mountainous areas based on surface to subsurface spectral ratios of KiK-net seismograms

山地斜面等のKiK-netで観測された多数の地震について, 加速度振幅のフーリエスペクトルに関する地表と地中のスペクトル比 (SR) を求め, 周波数ごとの平均を平均スペクトル比 (ASR) とした。さらに, 周期0.1～0.5秒間の平均値を平均スペクトル比強度 (ASRI) とし, 地震動増幅の指標とした。ASRIと地盤指標としての30m深平均S波速度 (AVS30) との間に明瞭な負の相関がみられ, 近似的には山地においても地震動増幅の指標としてAVS30が適用できることが推定された。一方, ASRIと地形指標の曲率との間には, 弱い正の相関がみられた。また山地斜面の地形の影響が示唆されるケースもあった。しかし, ASRが山地斜面以外と大差ない山地斜面が多数存在することから, 山地斜面の揺れやすさは限定的であることが推定された。

Study on the Seismic Effect of the Pebble Soil Site in the Zhongwei Basin

Based on a large amount of drilling and geophysical exploration work in the Zhongwei Basin, and combined with the collected borehole data of a seismic safety assessment, this paper summarizes and builds 16 typical pebble soil layer calculation models. The effects of the thickness of the pebble layer, the thickness of the overlying silty clay, the top interface of the pebble layer on the peak acceleration and the response spectrum of the site seismic response were analyzed using the equivalent linearization method of the one-dimensional soil layer seismic response. The analysis results showed that the variation in pebble layer thickness had no obvious effect on the peak acceleration of the ground surface under different inputs; the influence of the pebble layer thickness on the ground acceleration response spectrum was primarily concentrated in the middle/high-frequency band of 0.2–0.6 s. Within this range, the acceleration response spectrum of the site with a 30 m pebble layer thickness was small, and the response spectrum curve showed a “trough” shape with a certain “weak isolation” effect. Under the same pebble layer thickness, the upper ground surface peak acceleration with a silty clay layer thickness increased with the increase in the central basin pebble soil field, where a short cycle of the seismic wave amplification effect was more obvious. The response spectrum peak period points were within 0.1–0.2 s and were influenced by the action of rare earthquakes. Moreover, the response spectrum curve showed a more obvious phenomenon of “twin peaks”, and the second peak point appeared in the period of 0.5–0.7 s. With the increase in the input intensity, the PGA amplification ratio of the pebble-top interface was significantly smaller than that of the site surface; under different intensities of input, the acceleration response spectrum of the pebble-top interface showed a “trough” phenomenon that was lower than the bedrock input at approximately 0.1 s. Under the action of rare ground motion, the acceleration response spectrum curve of the pebble-top interface showed a “double peak” phenomenon, and within 0.24–0.4 s, the spectrum value was lower than the bedrock input, showing an obvious shock absorption and isolation effect. Under the action of an earthquake, the energy of the pebble-top interface was concentrated in the low-frequency range of 1.1–2.2 Hz, and the amplification effect was obvious. In the range of 8–10 Hz, the amplitude was lower than the bedrock input, and the seismic isolation effect was obvious.

Effects of Lunar Near‐Surface Geology on Moonquakes Ground Motion Amplification

AbstractLunar seismology has focused on exploring the Moon's seismic activity and its internal structure. However, less attention has been given to site specific, near‐surface geology‐related amplification of seismic waves on the Moon. Here, we quantified ground‐motion amplifications of seismic waves due to local site conditions at the Apollo landing sites. We analyzed Apollo Passive Seismic Experiments seismometer recordings of 30 artificial and natural impacts and estimated the mid‐period (0.1–3 Hz) ground‐motion amplification at each site. We applied techniques commonly used in engineering seismology to understand the local site effects, such as the Horizontal over Vertical Spectral Ratio (HVSR) and the Reference Site Method (RSM) on lunar seismic data. The HVSR and the RSM show convergent spectral ratios specific for each landing site. To correlate these empirical results estimated from lunar artificial and meteoroid impact events with the local site geology, we simulated ground motion amplification using 2D finite difference modeling of lunar geological models and estimated the best geological setting capable of producing a similar frequency response to those observed at each Apollo landing site. Correlation results from the empirical methods and the simulated models show similarities ranging between 79% and 92%, a correlation more than 90% between the RSM and the HVSR results, and similarity exceeding 96% between RSM estimations using different reference sites. These results demonstrate the prominence of a local site geology dependent amplification for frequencies between 0.1 and 3 Hz.

Evaluation of Field Shear Wave Velocity in Deep Soil Mixing Based on Laboratory Studies

One of the reasons behind the stabilization of soft and problematic soil by deep soil mixing is to reduce the amplification of seismic waves which arrive to the ground surface and foundation of buildings. Therefore, it is important to correctly predict the dynamic properties of the improved ground. To address the dynamic properties of deep soil mixing, this paper evaluates the in-situ shear wave velocity of deep soil mixing (Vs-field) based on laboratory investigation (Vs-lab). The conversion factors, relating to the shear wave velocities of laboratory and field, have been obtained based on a variety of tests including bender element, pulse velocity, and low-amplitude dynamic tests in the resonance column. In this study, the effect of confinement and vertical stress on the dynamic properties of the base stabilized using deep soil mixing technology was evaluated. These effects were combined with the known disturbance and aging influence which is available in the literature. The research has shown that the most significant factors affecting the shear wave velocity are confinement stress and additional vertical load, which lead to 43% and 17.5% increase respectively.

Seismic Active Pressure on an Inclined Retaining Wall with Surcharge on a Submerged Backfill

Seismic design of retaining wall supporting submerged retaining wall requires precise estimation of lateral earth pressure considering realistic parameters that constitute hydro-dynamic pressure, frequency inputs and other dynamic properties. The purpose of this study is to establish a closed-form solution for seismic lateral earth pressure acting on a retaining wall with submerged backfill with surcharge. The proposed method includes the dynamic nature by considering time-period, the frequency of the seismic wave, dynamic soil properties. Boundary conditions in the backfill are satisfied due to the propagation of the seismic wave. This study considers amplified seismic waves to estimate inertial forces due to critical soil mass and surcharge. The excess pore pressure generated during the seismic action is also considered in this study. The obtained formulation shows the significant effect of frequency content, damping resistance offered by backfill soil, amplification of seismic wave on seismic earth pressure. The seismic earth pressure obtained from this study is observed to be in a close agreement with centrifuge test results and analytical studies from the literature. This study definitely addresses the lateral pressure distribution on the retaining wall with backfill submergence and surcharge on the surface.

Site Effects Study in the Peshawar District using Seismic Noise

Surficial geology plays an important role during earthquakes in terms of its impact on the resulting ground shaking, referred to as site effects. Site effects influence the level of earthquake hazard and risk in a region. Peshawar, the provincial capital of Khyber Pakhtunkhwa, is one of the most seismically active cities in Pakistan. However, it lacks any such seismic characterization. In this work, a seismic ambient noise study was performed in Peshawar using observations from a total of 92 stations. The seismic noise data is recorded using a broadband seismometer for a period of about 30 minutes at every station point. The fundamental resonance frequency and a first-order amplification based on the seismic noise recording are estimated using the method of Nakamura. First-order estimates of the amplification range from 1.0 to 7.0, whereas the resonance frequency ranges between 0.2 to 2.5 Hz. The results suggest a complex geological structure with low seismic impedance and deep soil deposits in Peshawar. The depth of soil deposits is estimated to be more than 300 m, leading to a potential amplification of low-frequency seismic waves. These findings are crucial for tall structures with fundamental vibration periods greater than 0.40 sec. Doi: 10.28991/CEJ-2022-08-04-010 Full Text: PDF