Analysis Of Site Effects Research Articles

Analysis of local site effects on seismic ground response under Boumerdes earthquake scenario: case study of Zeralda site of Algeria

Analysis of local site effects on seismic ground response under Boumerdes earthquake scenario: case study of Zeralda site of Algeria

Unraveling the Seismic Source in Archaeoseismology: A Combined Approach on Local Site Effects and Geochemical Data Integration

Archaeoseismological research often deals with two unresolved questions: the magnitude and level of damage caused by past earthquakes, and the precise location of the seismic source. We propose a comprehensive review of an integrated approach that combines site effects with the analysis of geochemical data in the field of archaeoseismology. This approach aims to identify active buried faults potentially related to the causative seismic source and provide insights into earthquake parameters. For each integrated method, we report the foundational principles, delineation of theoretical field procedures, and exemplification through two case studies. Site effects analysis in archaeoseismology assumes a pivotal role in unraveling historical seismic occurrences. It enables estimating the earthquake magnitude, assessing the seismotectonic patterns, and determining the resulting damage level. Valuable data related to earthquake parameters can be extracted by analyzing vibration frequencies and acceleration measurements from structures within archaeological sites. This information is instrumental in characterizing seismic events, evaluating their impact on ancient structures, and enhancing our understanding of earthquake hazards within the archaeological context. Geochemical investigations supply indispensable tools for identifying buried active faults. The analysis of fluids and gases vented in proximity to faults yields valuable insights into their nature, activity, and underlying mechanisms. Faults often manifest distinctive geochemical imprints, enabling the differentiation between tectonically active and volcanically related fault systems. The presence of specific gases can further serve as indicators of the environmental conditions surrounding these fault networks. Integrating site effects analysis and geochemical investigations within archaeoseismological research is crucial to improving our understanding of unknown past earthquakes. Moreover, it enhances the seismic hazard assessment of the region under study.

The 2023 Turkey–Syria Earthquake Sequence: Ground-Motion and Local Site-Effect Analyses for Kahramanmaras City

The 2023 Turkey–Syria Earthquake Sequence: Ground-Motion and Local Site-Effect Analyses for Kahramanmaras City

Regional zonation based on seismic vulnerability using local site effect analysis and potential damage to the city of Medan (North Sumatra, Indonesia) due to earthquake

BackgroundMicrozonation becomes important for big cities like Medan (North Sumatra, Indonesia) as population agglomeration increases in urban areas resulting in rapid and unplanned construction. Mitigation efforts must be carried out to minimize losses arising from earthquakes, such as loss of life and environmental damage, and it can be done by analyzing seismic susceptibility and local site effects.PurposeThis study analyzes the potential for environmental damage caused by seismic hazards in the city of Medan, North Sumatra, Indonesia. The purpose of this study is to provide an overview of the definition and methodology of seismic–geotechnical hazard zoning and the methodology used for making seismic hazard maps with the case study of Medan City.MethodsWhile determining the zoning, microzonation measurements and environmental data parameters are involved. To obtain comprehensive results, microzonation measurements were carried out using three methods, namely the Multichannel Seismic Analysis Surface Wave (MASW), Spatial Autocorrelation (SPAC), and Horizontal-To-Vertical Spectral Ratio (HVSR) with 200 measuring points spread throughout the city of Medan. Parameter weighting values such as population, site class, seismic susceptibility, dominant period, land cover, slope, and weather class were obtained using the analytic hierarchy process (AHP) method.ResultsWe presented the result of the survey, including the MASW, SPAC, and HVSR results. In general, medium soil and soft soil dominate almost all areas of Medan city. The estimated depth of engineering bedrock is at a depth of about 291.33 – 735.87 meters from the ground surface. The dominant period values ranged from 0.0907 s to 8.30723 s.ConclusionsWe classified Medan City (North Sumatra) into several zones, based on their seismic vulnerability using local site effect analysis and potential damage due to earthquakes. This study is necessary for future seismic hazard assessment.

Sex‐related differences in premature cardiovascular disease in familial hypercholesterolemia

BackgroundFamilial hypercholesterolemia (FH) is associated with an increased prevalence of premature atherosclerotic cardiovascular disease (ASCVD), however, little is known about sex-specific differences in premature ASCVD and its risk factors. ObjectiveThe present study seeks to assess the burden and risk factors for premature ASCVD among men and women with FH. MethodsIn this study we retrospectively examined sex-specific differences in ASCVD prevalence, risk factor burdens, and lipid treatment outcomes in 782 individuals with clinically or genetically confirmed FH treated in 5 U.S. lipid and genetics clinics. A generalized linear model using Binomial distribution with random study site effect and sex-stratified analysis was used to determine the strongest predictors of premature ASCVD, and lipid treatment outcomes. Covariates included age, sex, diabetes mellitus (DM), hypertension, and current smoking. ResultsAmong the cohort, 98/280 men (35%) and 89/502 women (18%) had premature ASCVD (defined as <55 years in men and <65 years in women). Women with premature ASCVD had higher mean treated total cholesterol (216 vs. 179 mg/dl, p=<0.001) and LDL-C (135 vs. 109 mg/dl, p= 0.005). ConclusionThese data confirm that high percentages of women and men with FH develop premature ASCVD, and suggest that FH may narrow the observed sex difference in premature ASCVD onset. These data support more aggressive prevention and treatment strategies in FH, including in women, to reduce non-lipid risk factors and residual hypercholesterolemia.

Analysis of Local Site Effects in the Međimurje Region (North Croatia) and Its Consequences Related to Historical and Recent Earthquakes

The Međimurje region (North Croatia), situated between the Drava and Mura rivers with a slightly elevated hilly area, can be generally characterized as a low-seismicity area. However, macroseismic observations from historical and recent earthquakes indicate that some localities in this region are more prone to damage than others. Significant damage and the observed higher intensities in the Međimurje region after the historical earthquakes of 1738 MLm5.1 (Međimurje) and 1880 ML6.3 (Zagreb), and events that occurred in the instrumental era, 1938 ML5.6 (Koprivnica), 1982 ML4.5 (Ivanec), and the most recent 2020 ML5.5 Zagreb and 2020 ML6.2 Petrinja earthquakes, point to the influence of local site effects. There is a reasonable indication that these earthquakes involved several localized site effects that could explain the increased intensity of half a degree or even up to one degree at certain localities compared to macroseismic modeling for rock condition. To better understand the influence of local site effects in the Međimurje region, the single-station microtremor Horizontal-to-Vertical Spectral Ratio (HVSR) method for subsurface characterization was used. Based on individual measurements, microzonation maps were derived for the Međimurje region to better understand the behavior of ground motion and the influence of local site conditions in comparison to macroseismic intensities and past damage observations. Several local site effects could be interpreted as a main contribution to site amplification and resonance effects due to variations in deep soft-deposit thicknesses overlayed on hard deposits and directional variations in topographical areas that could localize earthquake damage patterns. Correlations of microtremor analysis with intensity observations from historical earthquakes as well with recent earthquakes could help to distinguish local site zones prone to the possible occurrence of higher earthquake damage from nearby and distant earthquakes.

Locating the Source Regions of the Single and Double-Frequency Microseisms to Investigate the Source Effects on HVSR in Site Effect Analysis

Locating the Source Regions of the Single and Double-Frequency Microseisms to Investigate the Source Effects on HVSR in Site Effect Analysis

Abstract 9843: Sex-Related Differences in Premature Cardiovascular Disease in Individuals with Familial Hypercholesterolemia

Background: Familial hypercholesterolemia (FH) is associated with elevated risk for premature atherosclerotic cardiovascular disease (ASCVD) (&lt;55 years in men and &lt;65 years in women). Little is known about sex-specific differences in risk factors and treatment outcomes in individuals with FH and premature ASCVD. Objective: To characterize sex-specific risk factor burdens and treatment outcomes in individuals with FH and premature ASCVD. Methods: The prevalence of premature ASCVD in 782 adults with FH (diagnosed by clinical scores and/or genetic testing) from 7 US-based lipid clinic practices was assessed retrospectively. A multivariate logistic mixed effects model with random study site effect and sex-specific analysis was used to determine the strongest predictors of premature ASCVD, and lipid treatment outcomes. Covariates included age, sex, diabetes mellitus (DM), hypertension (HTN), and current smoking. Results: 98/280 men and 89/502 women had premature ASCVD. Women with premature ASCVD were older by an average of 3 years (mean age 58 vs. 55 years, p= 0.04) and had higher on treatment total cholesterol (216 vs. 178 mg/dl, p&lt;0.001) and LDL-C (135 vs. 109 mg/dl, p= 0.005) (Table 1). In men, the strongest predictors of premature ASCVD were HTN (OR 5.39, 95% CI 2.85, 10.93, p&lt;0.001) and DM (OR 2.25 95% CI 1.17, 4.37, p=0.016). In women, the strongest predictors of premature ASCVD were HTN (OR 5.48, 95% CI 3.22, 9.71, p&lt;0.001) and smoking (OR 2.85, 95% CI 1.35, 5.94, p=0.005). Treated LDL-C was not a significant predictor of ASCVD in either men or women. Conclusion: The normal delay in age of onset of ASCVD in women vs. men may be shortened in individuals with FH. Both women and men with FH have an increased risk of premature ASCVD in the setting of HTN, but risks from smoking and DM differ by sex. Women with FH and premature ASCVD had higher on-treatment LDL-C. Aggressive treatment strategies are needed to reduce risk factor burdens and residual hyperlipidemia in these patients.

Mesoscale seismic hazard zonation in the Central Seismic Gap of the Himalaya by GIS-based analysis of ground motion, site and earthquake-induced effects

Mesoscale seismic hazard zonation in the Central Seismic Gap of the Himalaya by GIS-based analysis of ground motion, site and earthquake-induced effects

Polarization characteristics of Rayleigh waves to improve seismic site effects analysis by HVSR method

The horizontal-to-vertical spectral ratio (HVSR) method based on ambient noise recordings is a popular and efficient approach to estimate the seismic site effect parameters. This method is sufficiently robust in determining the predominant frequency (f0) of the site, whereas its estimate of the amplification factor lacks consistency because generation mechanisms, source locations and proportions of the wave types making up ambient noise vary locally and are not well understood, in addition to lack of clarity in the theory of the HVSR method. As the generation mechanisms, source locations and wave compositions of the single- and double-frequency (SF and DF respectively) microseisms (0.05–0.5 Hz) are better studied compared to the noise in other frequency bands, this study focuses on investigating the site effects on the fundamental Rayleigh (Rg) waves in the SF and DF microseisms recorded at 30 Transportable Array stations in the east coast of the United States. HVSRs are calculated first to obtain f0s as well as the unconsolidated sediment thicknesses (USTs). Then the polarization analyses are carried out to select the ellipsoids approximating the particle motions of the Rg waves and to estimate the HVSR of these Rg ellipsoids (HVSRR). The polarization parameters and HVSRR indicate that the Rg waves' particle motions form oblate ellipsoids in the UST range whose f0 values fall within the DF band. Comparison of the observed HVSR and HVSRR and the computed HVSR values based on the body wave and the Rayleigh wave theories shows that the observed HVSR in the DF band on bedrock and/or thin unconsolidated sediments are mainly due to the ellipticity of Rg waves, while those on thick unconsolidated sediments whose f0 values fall within the DF band result from the combined effects of the ellipticity of Rg waves and multiple reflection of S-waves. This outcome will help develop procedures to improve the consistency of HVSR's amplification estimates and hence its reliability in seismic site effects analysis.

Joint multizonal transdimensional Bayesian inversion of surface wave dispersion and ellipticity curves for local near-surface imaging

SummaryPhysical properties of near-surface soil and rock layers play a fundamental role in the seismic site effects analysis, being an essential element of seismic hazard assessment. Site-specific mechanical properties (i.e. shear- and compressional-wave velocities and mass density) can be inferred from surface wave dispersion and horizontal-to-vertical or ellipticity data by non-linear inversion techniques. Nevertheless, results typically exhibit significant inherent non-uniqueness as different models may fit the data equally well. Standard optimization inversion techniques minimize data misfit, resulting in a single representative model, rejecting other models providing similar misfit values. An alternative inversion technique can be formulated in the Bayesian framework, where the posterior probability density on the model space is inferred. This paper introduces an inversion approach of surface wave dispersion and ellipticity data based on a novel multizonal transdimensional Bayesian formulation. In particular, we parametrize 1-D layered velocity models by the varying number of Voronoi nuclei, allowing us to treat the number of layers as an unknown parameter of the inverse problem. The chosen parametrization leads to the transdimensional formulation of the model space, sampled by a reversible jump Markov chain Monte Carlo algorithm to provide an ensemble of random samples following the posterior probability density of model parameters. The used type of the sampling algorithm controls a model complexity (i.e. the number of layers) self-adaptively based on the measured data's information content. The method novelty lies in the parsimonious selection of sampling models and in the multizonal formulation of prior assumptions on model parameters, the latter allows including additional site-specific constraints in the inversion. These assumptions may be based on, e.g. stratigraphic logs, standard penetration tests, known water table, and bedrock depth. The multizonal formulation fully preserves the validity of the transdimensional one, as demonstrated analytically. The resultant ensemble of model samples is a discrete approximation of the posterior probability density function of model parameters and associated properties (e.g. VS30, quarter-wavelength average velocity profile and theoretical SH-wave amplification function). Although the ultimate result is the posterior probability density function, some representative models are selected according to data fit and maximum of the posterior probability density function. We first validate our inversion approach based on synthetic tests and then apply it to field data acquired from the active seismic survey and single-station measurements of ambient vibrations at the SENGL seismic station site in central Switzerland.

Simulations of ground motions under plane wave incidence in 2D complex site based on the spectral element method (SEM) and multi-transmitting formula (MTF): SH problem

Recent ground motion simulations based on the spectral element method have mainly focused on source-internal problems. Reports on seismic responses due to plane wave incidence are rare, even though these are frequently encountered in site effect analysis and soil-structure interaction simulations. In this study, a seismic motion simulation method for 2D complex sites under plane SH wave incidence is proposed based on high-precision spectral element method (SEM) and multi-transmitting formula (MTF). The accuracy and stability of this method are validated through numerous numerical examples. Comparisons with analytical solutions and extended results demonstrate the high simulation accuracies for the ground motions in 2D complex site models when SH plane waves are vertically incident from the bottom. Compared with MTF in the traditional finite-element method (FEM), MTF integrated into SEM demonstrates better performance for both high- and low-frequency stabilities. First, until to the third-order MTF, this method shows a fairly good ability to eliminate high-frequency instability. This instability only occurs when the artificial wavespeed, ca, adopted in the MTF is larger than about five times the physical velocity, cs. For the most common case of ca = cs, long-term stable results can be achieved without any special treatments. In addition, under the condition of no interventions, the low-frequency drift instability for MTF in SEM is considerably lessened compared with that of MTF in FEM, and the drift instability can also be eliminated by a smaller perturbation parameter than in the latter. The method presented in this study combines the advantages of SEM and MTF, and exhibits better stability performance, indicating good application prospects for wave motion simulations of plane wave incidence problems.

Application of horizontal to Vertical Spectral Ratio microtremor technique in the analysis of site effects and structural response of buildings in Querétaro city, Mexico

Querétaro city is situated in the north central part of the Trans-Mexican Volcanic Belt, and it was considered by several previous studies as an aseismic region. Since that, as well as considering the surrounding seismotectonic setting, it was significant to assess the seismic hazard across the city which aids in the development and updating the building codes and the seismic design criteria. In this regard, the Horizontal to Vertical Spectral Ratio (HVSR) Nakamura's technique has been applied to investigate the local-site effects across the city. Microtremor measurements were performed at 76 free-field selected sites, through the implementation of portable seismic stations equipped with three-component velocity sensors of Trillium Compact 120 s broadband seismometer. Then, acceleration values were estimated by generating synthetic accelerograms based on a recently-developed algorithm that combines the HVSR technique and the theory of random vibrations, considering as a reference the September 19, 2017 (Mw 7.1) intraslab earthquake recorded at the Centro de Geociencias (CGEO) Seismic Station, in Juriquilla, Querétaro. Finally, by computing the pseudoacceleration response spectra through the linear acceleration method at structural periods of 0.1, 0.5, 1.0, 2.0, and 5.0 s, corresponding seismic hazard maps were established for the studied region. Based on these values and delimiting the areas with higher risk considering the interaction of the soil with the buildings on it, this article is the basis for delimiting seismic parameters that define the city, with future applications in the seismic engineering considering both linear and nonlinear structural behaviors.

Development of an MTF in ADINA and its application to the study of the Yuxi Basin effect

A three-dimensional multitransmitting formula is developed in ADINA to simulate the input of seismic waves and the scattering of infinite domains at the same time, consistent with the progress of the explicit finite element method of lumped mass. A three-dimensional cube model is built, and a delta pulse wave is input to compare the simulation results with the analytical solutions. The simulation results show that the peak error is 0.2% of the input wave, which meets the requirements of the usual numerical simulation. This method has a certain efficiency advantage in site effect analyses of fine models for localized fields. A velocity structure model of the Yuxi Basin is built, and the associated basin effect is studied by numerical simulation. The distribution of the focusing effect is related to the structure of the narrow east-west and wide north-south features in the Yuxi Basin, and the edge effect is related to the slope of the basin base. A distribution map is given of the amplification effect of ground motion in the basin.

Site Effects Analysis of Shallow Subsurface Structures at Mashiki Town, Kumamoto, Based on Microtremor Horizontal-to-Vertical Spectral Ratios

ABSTRACTIn this study, we conducted a series of microtremor surveys to understand the contribution of soil amplifications to the heavy structural damage of wooden houses in downtown Mashiki, Kumamoto, Japan, during the 2016 Kumamoto earthquake. We analyzed the microtremor horizontal-to-vertical spectral ratios (MHVRs) of each observation site. A few previous studies have demonstrated the applicability of the earthquake horizontal-to-vertical spectral ratios (EHVRs) to identify velocity structures. Therefore, we transformed the MHVRs into pseudo-EHVRs (pEHVRs) using the EHVR-to-MHVR ratio (EMR) method. We identified the velocity structures in Mashiki, according to the diffuse field concept (DFC) for earthquake, using the pEHVRs. We also estimated the seismological bedrock motions during the mainshock based on the DFC. We then performed the seismic ground response analyses of subsurface structures, using a 1D linear analysis and an equivalent linear analysis (ELA). Finally, we obtained the distribution maps of peak ground acceleration (PGA) and peak ground velocity (PGV) for Mashiki town. We obtained the following results: (a) the thickness of the soft sediment under the southwestern part of Mashiki is deeper than that under the northeastern part; (b) the thickness of the soft sediments was a primary cause of the heavy damage to buildings of Mashiki; (c) the ground motions estimated by the ELA method seemed to be close to the observed seismic ground motions in Mashiki; (d) the distribution of the estimated PGV in Mashiki had a close relationship with the damage ratio distribution of buildings; (e) the EMR method, along with the DFC for earthquake and the 1D ELA method, successfully simulated the strong motions that occurred during the mainshock in Mashiki.

Numerical Analysis of Seismic Site Effects in Loess Region of Western China under Strong Earthquake Excitations

The Loess Plateau is one of the most tectonically and seismically active areas in the world. Observations from past strong earthquakes, particularly the Minxian–Zhangxian and Wenchuan earthquakes, have shown distinctive evidence of seismic site effects in the mountainous area of southeastern Gansu province. In this study, seismic damage in the loess areas of southeastern Gansu province induced by these earthquakes was investigated and briefly described. Different types of ground motion were selected, and the one-dimensional equivalent linear method was used for numerical analysis of the ground motion effects in the loess regions. Moreover, seismic response analysis of a typical loess tableland was conducted. The results showed that the seismic responses of a typical loess tableland under different seismic excitations have totally different dynamic characteristics. Moreover, the seismic damage in loess regions was more serious under far-field seismic excitation compared with near-field seismic excitation with the same peak acceleration. Through this study, the quantitative assessment of ground motion effects can be approximately estimated and the mechanism of site amplification effects on ground motion is further explained.

Horizontal-to-Vertical Spectral Ratio (HVSR) IRIS Station Toolbox

AbstractThe horizontal-to-vertical spectral ratio (HVSR) for seismic ambient noise is a popular method that can be used to estimate the predominant frequency at a given site. In this article, we introduce the Incorporated Research Institutions for Seismology (IRIS) Data Management Center’s (DMC’s) openly available HVSR station toolbox. These tools offer a variety of ways to compute the spectral ratio by providing different averaging routines. The options range from the simple average of spectral ratios to the ratio of spectral averages. Computations take advantage of the available power spectral density estimates of ambient noise for the seismic stations, and they can be used to estimate the predominant frequency of the many three-component seismic stations available from the IRIS DMC. Furthermore, to facilitate the identification of the peaks in HVSR profiles for the assessment of the predominant frequency of station sites, the toolbox can also process the results of HVSR analysis to detect and rank HVSR peaks. To highlight the toolbox capabilities, three different examples of possible use of this toolbox for routine site-effect analysis are discussed: (1) site effects related to thawing in Arctic regions, (2) ground-motion amplification in urban area, and (3) estimation of station VS30.

Anti-plane responses of acceleration by a shallow hill next to an alluvial valley

This study proposed a hybrid method combining finite element method (FEM) and a wave function based on the Lamb series in conjunction with modified transfinite interpolation for use in examining surface accelerations on a semi-elliptical hill subjected to shear horizontal (SH) waves of various dimensionless frequencies (η) at various incident angles (θ). The case topography included a semi-elliptical hill of fixed height adjacent to a semi-elliptical alluvial valley of variable depth (EHAV). Differences in site effects between EHAV and a single semi-elliptical hill (or a semi-elliptical alluvial valley) were investigated as a function of the modified transmissibility (TR). Variations in TR associated with η clearly revealed the resonance frequencies (RFs), associated with an elevated probability of landslides. Our simulation results revealed a larger number of RFs form in hills adjacent to AV than in isolated hill. This study proposes a systematic approach for the analysis of site effects of EHAV, focusing on the identification of potential landslides due to seismic waves excitation.

Seismic hazard analysis and local site effect of the 2017 Mw 7.3 Sarpol-e Zahab, Iran, earthquake

A strong earthquake occurred on November 12, 2017, in Sarpol-e Zahab city, western Iran, with the moment magnitude ( $$M_{{\text{w}}}$$ ) of 7.3 and a focal depth of 18 km. The maximum horizontal peak ground acceleration of 0.69 g was recorded at the Sarpol-e Zahab station. Significant damages were observed in frame and masonry buildings, while the damage distribution was non-uniform throughout this small city. The preliminary site reconnaissance revealed that numerous engineering structures collapsed or considerably damaged in some regions, contrary with those non-structural masonry buildings in other regions which remained intact during earthquake. This paper represents a preliminary reconnaissance report prepared through the site visit done by the authors, a few days following the earthquake occurrence. Then, the data recorded by the strong ground motion stations in the affected city and the surrounding regions together with the geotechnical data gathered from the available boreholes in Sarpol-e Zahab are incorporated for probabilistic seismic hazard and local site effect analyses. The observed response spectra at two stations and distance-dependency of ground acceleration are compared with those predicted by some attenuation models. The results of probabilistic seismic hazard analysis in the return periods of 475 and 2475 years are compared with the observed ground response and the design spectra recommended by the Iranian seismic code (for site classes Types I and II). Several geotechnical boreholes from the previous works in the affected area were analyzed through the equivalent-linear site response approach in order to obtain the seismic response at the soil surface. The results are then compared with the code design spectra for the site classes of Types III and IV. It is demonstrated that the calculated response spectra are generally larger than those recommended by the Iranian seismic code, especially for the 4–7 stories buildings.

Basin edge effect on industrial structures damage pattern at clayey basins

In this numerical study, the 2D dynamic behavior of a clayey basin and its effect on damage pattern over basin edge are investigated. To attain this goal, a fully nonlinear time domain analysis method has been applied. Then, the fragility curves of the considered two typical industrial structures for that certain point are estimated using the acceleration time histories recorded at each surface point. The results show that the use of the damage related parameters in site effect analyses, instead of amplification curves, can yield more realistic estimation of the basin dynamic response. In a distance about 150m from outcrop at the basin edge, the differences between fragility curves increase when increasing the distance from outcrop with respect to the reference rock site. Outside this region and towards the basin center, they tend to occur in rather single curves. Furthermore, to connect the structural damage to the basin edge effect, the earthquake demand value at different points for two typical structures was evaluated. It was seen that the probability of occurrence of damage increases over 250 m from outcrop, while the effect of the basin edge was limited to 150 m in case of the basin edge evaluation by using fragility curves.