Soil Transfer Functions Research Articles

Assimilating Seismic Data And Soil Basic Information to Predict Near-surface Permeability And Water Content

Soil permeability plays a key role in the study of earth sciences for agriculture and forestry. Because the traditional laboratory measurement is time-consuming and laborious, and only discrete profile data can be obtained. In this paper, a simple and efficient method using soil transfer function (PTFs), is proposed to estimate permeability and other parameters indirectly by seismic wave observation. Based on Biot’s theory establishing the relationship between shear-wave velocity and permeability, and the basic soil information in the study area, including land survey, logging and drilling data, using the PTFs constraint to estimate saturated hydraulic conductivity, soil components, saturated water content and residual water content may favor the physical corrections of the PTFs. The results show that there are three distinct layers of permeability in the study area, consistent with the velocity structure. The measured basic information further verifies the accuracy of the saturated permeability coefficient estimation, which shows the reliability of the improved PTFs. The established near surface permeability estimation method by integrating seismic wave observation and soil basic information may provide further assimilation for parameter estimation combining geophysical observation and hydrogeographic statistics.

Short-time frequency-domain method for truly nonlinear dynamic ground response analysis: The equivalent-nonlinear approach

Evaluating soil nonlinearity during cyclic loading is one of the most significant challenges in ground response analysis, especially when dealing with the inverse problem of deconvolution. Different schemes have already been developed for dynamic ground response analysis, both in the time and the frequency domain. The most accurate method to account for soil nonlinearity is the nonlinear dynamic analysis in the time domain. This approach is based on nonlinear constitutive models capable of accurately simulating highly nonlinear problems like soil liquefaction. However, the time-domain analysis is suitable only for the convolution analysis to define the ground motion at the free surface of a soil deposit from the bedrock motion. The frequency-domain analysis is the most common solution for the inverse problem called deconvolution, which is used to define the bedrock motion from the free surface ground motion. A well-known approach developed in the frequency domain for ground response analysis is the equivalent-linear method (EQL). This approach adopts an iterative procedure to define elastic shear modulus and damping ratio compatible with the induced strain level. Still, it presents some limitations, especially for highly nonlinear soil response, due to the use of strain-compatible but constant soil properties. This article presents a new scheme to conduct truly nonlinear dynamic analysis in the frequency domain based on the new concept of the short-time transfer function. Unlike the EQL method, which uses a constant transfer function, the proposed approach, called the “Equivalent-Nonlinear” method (EQNL), defines a soil transfer function evolving in time, depending on the shear stress and strain demands. The EQNL method approximates the response of a nonlinear system as an incrementally changing viscoelastic system and could represent a valuable tool for nonlinear deconvolution. This article shows the analytical formulation and the first set of validations of the EQNL approach, with detailed comparisons with the EQL and NL methods and vertical array data. These comparisons show the potentialities of the EQNL approach to reproduce the results of the nonlinear dynamic analysis. The EQNL approach has been implemented in MATLAB, and the source code is provided as supplementary material for this article. A more comprehensive validation is underway, aiming to better characterize the limitations and the capabilities of the method.

Effect of water table level on metro-induced vibrations received by adjacent historical buildings

One of the main concerns in development of metros in historical cities is adverse effects of train-induced vibrations on Cultural and Historical Structures (CHS). In this regard, several approaches have been developed in the literature to predict the level of railway-induced vibration received by CHSs. One of the main limitations of the proposed prediction approaches is a lack of consideration of the effect of variation of water table level on the railway-induced vibrations. To fill this gap, a comprehensive field measurement was carried out in this research in the historical city of Isfahan. Based on the data obtained from the field measurement, significant effects of variation of water table level on the Peak Particle Velocity (PPV) and Soil Transfer Function (STF) were shown. Using the result obtained from the measurement, an adjustment factor was derived to consider the effect of variation of water table level in the conventional train-induced vibration prediction approach. The accuracy and validity of the water table level adjustment factor derived in this study were evaluated through an independent comprehensive field measurement performed in a different historical city.

Investigation of parameters affecting the soil amplification by means of 1-D analysis

The increase in the amplitude of earthquake waves as they pass through layers of soft soil close to the surface can have significant effects on ground amplification and structural damage. The aim of this study is; ground response analysis was performed using 1D (One Dimensional) Equivalent Linear Analysis method with DeepSoil software for specific soil profiles. The analyses were carried out with 3 different strong ground motions selected in accordance with the response spectrum. Strong ground motion records selected according to the regulation were scaled in accordance with the spectrum in the frequency domain. Analysis results were compared with the Turkish Earthquake Response Regulations 2018 (TEBR 2018). It is explained how the soil transfer functions, namely how the amplification functions vary depending on the parameters of the soil layer thickness and shear wave velocity. Depending on the characteristics of the soil profile, it has been observed that the incoming earthquake waves only amplify those in a certain frequency range. By performing ground response analysis, it should be known which frequency content of the ground amplification and therefore which types of structures will affect and the design should be made by considering these criteria.

Identifying marine and freshwater overprints on soil-derived branched GDGT temperature signals in Pliocene Mississippi and Amazon River fan sediments

The fractional abundance of branched glycerol dialkyl glycerol tetraether (brGDGT) membrane lipids in coastal marine sediments has been posited as a proxy for the reconstruction of terrestrial temperatures on the nearby land, based on the assumption that they are produced in soils and delivered to the marine realm by rivers following erosion. Here, we test the suitability of brGDGTs as a continental paleothermometer in Pliocene age sediments from the northern Gulf of Mexico (GoM; speculated Mississippi River input) and the Ceará Rise (speculated Amazon River input). Low branched to isoprenoid tetraether (BIT) index values of 0.00–0.13 and the near absence of pollen and long-chain plant waxes in the GoM sediments suggest that the Mississippi River did not have a strong influence on the delivery of terrestrial organic matter to the site during the Pliocene and soil input was limited. Indeed, the high weighted average of cyclopentane-containing tetramethylated brGDGTs (#ringstetra) in the GoM sediments (0.50 ± 0.09) relative to that of modern soils from the Mississippi catchment (0.25 ± 0.16) indicates that the brGDGTs in the GoM sediments were mostly produced in situ in the marine realm, hampering reliable land temperature reconstruction using the global soil transfer function. In contrast, high BIT index values (0.46 ± 0.21) and low #ringstetra (0.25 ± 0.15) in sediments from the Ceará Rise suggest that these brGDGTs are primarily derived from soils. However, reconstructed temperatures were 11–18 °C lower than modern Amazon catchment temperatures. The relative abundance of 6-methylated brGDGTs (Isomerisation Ratio; IR) in the sediments is 0.82 ± 0.10, which resembles that of suspended particulate matter (SPM) in the modern Amazon River more than that of catchment soils (IR = 0.18 ± 0.18). This reveals that brGDGTs in the Ceará Rise sediments likely have a freshwater, riverine origin. Thus, the majority of the brGDGTs in both the GoM and Ceará Rise sediments are produced in situ, in the marine or river realms, which precludes application of the brGDGT paleothermometer. Our study shows that the sources of brGDGTs in coastal marine sediment archives must be critically evaluated prior to using the proxy for paleoclimate reconstruction.

Stratified Data Reconstruction and Spatial Pattern Analyses of Soil Bulk Density in the Northern Grasslands of China

The spatial pattern of soil bulk density in the grasslands of northern China largely remains undefined, which raised uncertainty in understanding and modeling various soil processes in large spatial scale. Based on the measured data of soil bulk density available from soil survey reports from the grasslands of northern China, we constructed a soil Stratified Pedotransfer function (SPTF) from the surface soil bulk density. Accordingly, the stratified bulk density data of soil vertical profile was reconstructed, and the estimation of soil bulk density data in horizontal space was performed. The results demonstrated that the soil bulk density of the grasslands of northern China was typically high in the central and northwestern regions and low in the eastern and mountainous regions. Mean soil bulk density of the grasslands was 1.52 g·cm−3. According to geographical divisions, the highest soil bulk density was observed in the Tarim basin, with mean soil bulk density of 1.91 g·cm−3. Conversely, the lowest soil bulk density was observed in the Tianshan Mountain area, with mean soil bulk density of 1.01 g·cm−3. Based on data obtained on various types of grasslands, the soil bulk density of alpine meadow was the lowest, with a mean soil bulk density of 0.75 g·cm−3, whereas that of temperate desert was the highest, with mean soil bulk density of 1.80 g·cm−3. Mean prediction error, root mean square deviation, relative error, and multiple correlation coefficient of soil bulk density data pertaining to surface layer (0–10 cm) in the grasslands of northern China were 0.018, 0.223, 16.2%, and 0.5386, respectively. The approach of employing multiple data sources via soil transfer function improved the estimation accuracy of soil bulk density from stratified soils data at the large scale. Our study would promote the accurate assessment of grassland carbon storage and fine land characteristics mapping.

3D Bedrock Structure of Bornova Plain and Its surroundings (İzmir/Western Turkey)

An earthquake record is needed on engineering bedrock to perform soil deformation analysis. This record could be obtained in different ways (seismographs on engineering bedrock; by the help of the soil transfer function; scenario earthquakes). S-wave velocity (V s) profile must be known at least till engineering bedrock for calculating soil transfer functions true and completely. In addition, 2D or 3D soil, engineering–seismic bedrock models are needed for soil response analyses to be carried out. These models are used to determine changes in the amplitude and frequency content of earthquake waves depending on the seismic impedance from seismic bedrock to the ground surface and the basin effects. In this context, it is important to use multiple in situ geophysical techniques to create the soil–bedrock models. In this study, 2D and 3D soil–bedrock models of Bornova plain and its surroundings (Western Turkey), which are very risky in terms of seismicity, were obtained by combined survey of surface wave and microgravity methods. Results of the study show that the engineering bedrock depths in the middle part of Bornova plain range from 200 to 400 m and the southern and northern parts which are covered limestone and andesite show the engineering bedrock (V s > 760 m/s) feature. In addition, seismic bedrock (V s < 3000 m/s) depth changes from 550 to 1350 m. The predominant period values obtained from single station microtremor method change from 0.45 to 1.6 s while they are higher than 1 s in the middle part of Bornova plain where the basin is deeper. Bornova Plain has a very thick sediment units which have very low V s values above engineering bedrock. In addition, it is observed sudden changes at the interfaces of the layer in horizontal and vertical directions.

Analysis of Soil Transfer Function in Izmir Metropolitan Area, Turkey

Analysis of Soil Transfer Function in Izmir Metropolitan Area, Turkey

Dynamic amplification factor concept of soil layers: a case study in İzmir (Western Anatolia)

Dynamic soil amplification factor (DAF) defining which ratio earthquake acceleration will reach the soil surface by changing is one of the most important factors in seismic risk studies. When computing the value of DAF at a point without a strong motion station, peak horizontal acceleration values (PGA) at the bedrock and soil transfer function are needed. PGA value at the bedrock can be obtained by using either real seismic records or the earthquake scenario. However, the soil transfer function (soil transfer function) can be computed observationally and theoretically. Observational soil transfer function is defined by microtremor horizontal/vertical spectral ratio. In case of theoretical computation, the density belonging to the soil layers between the bedrock and the soil surface is used together with the change of P-S wave rates with the depth and the damping factor. In this study, the dynamic amplification factor (DAF) has been computed and mapped for 57 points by using observational soil transfer functions obtained by microtremor horizontal/vertical spectral ratio as well as the earthquake scenario at a new city center located within the metropolitan area of Izmir. Also, theoretical soil transfer function at 1 point was obtained through spatial autocorrelation method (SPAC) study and determined to be compatible with observational result. It was observed that both peak period values are higher than 1 s and DAF values are higher than 2 throughout the area. Also, according to the soil profile obtained from the SPAC study, S wave rate changes up to a depth of 1300 m showing that acoustic impedance differences may occur in the frequencies and the magnitudes of the earthquake waves. The fact that peak period values obtained from microtremor studies are higher than 2 s supports this result. This means that acoustic impedance differences likely to occur in these depths should also be taken into consideration while computing the dynamic amplification factor.

Monitoring infiltration under a real on-site treatment system of domestic wastewater and evaluation of soil transfer function (Paris Basin, France)

The problem of evacuation of treated domestic wastewater has been investigated through a field study on a real undrained on-site treatment system (UOSTS). This system imposes a special mode of infiltration into the soil which is irregular. To characterize the hydraulic properties of this type of flow, soil texture, organic matter content and in situ saturated hydraulic conductivity (Ks) were measured for each 15 m2 of soil under the bottom of the UOSTS. In addition, the variation of water table and rainfall and the evolution of soil moisture and matrix potential were monitored using the sensors implanted under the system. The mean of the measured Ks is 100 times higher than values deduced from empirical pedotransfer functions based on the soil matrix properties. The measured Ks varies greatly in the 15 m2 area. Moreover, large and variable quantities of stone fragments (>2 mm) were found in the soil samples. These results suggest that a heterogeneous flow may occur in the stony soil via the macropores which shortcut the soil matrix. Indeed, according to their position, a non-uniform reaction of the sensors to the infiltration of treated wastewater was observed. In addition, two daily periodic peaks of water consumption in the house have been detected by the water content and tensiometer probes, confirming that the saturation rate is controlled by infiltration and not the water table.

Site effects evaluation in Málaga city’s historical centre (Southern Spain)

In this paper we present a site effects analysis carried out in Malaga city’s historical centre (Southern Spain). Two different methodologies have been used: an experimental technique using ambient noise measurements and a 1D numerical method. Soil fundamental frequencies have been obtained from the first technique, and soil transfer functions have been calculated from the numerical methodology. In order to use these results in vulnerability studies, intensity increments for each type of soil have also been estimated. From this information, a seismic microzonation has been proposed for the city centre, classified in six types of soils. Soil fundamental frequencies vary between above 5.0Hz at the hills of the city (where rock arises on the surface), and 1.0Hz near Guadalmedina river. The results show regions with high intensity increments (ΔI = +1.5) corresponding to areas which suffered heavy damage in the 1680 earthquake (Imax = VIII–IX). Moreover, most of the monuments and historical buildings in the city are located in these high risk areas. Results underline the importance of this kind of studies for seismic risk mitigation, historical preservation and emergency planning in the main cities’ historical centres.

The effect of road unevenness on the dynamic vehicle response and ground-borne vibrations due to road traffic

In this paper, the relation between road unevenness, the dynamic vehicle response, and ground-borne vibrations is studied. In situ measurements of road unevenness and the dynamic vehicle response for six roads with different types of pavement are supplemented by numerical predictions of ground vibrations. The predictions are performed in two stages. In the first stage, the dynamic vehicle response is computed based on the measured road unevenness. The vehicle model is validated by comparing the predicted and measured vehicle response and subsequently used to predict the dynamic vehicle loads. In the second stage, the dynamic road–soil interaction problem is considered and the transfer functions between the road and the soil are computed. The effect of the pavement type (continuous, jointed, or composed of individual pavers) on the road–soil transfer functions is investigated and the free field vibrations are calculated using the dynamic vehicle loads computed in the first stage. The predicted free field vibrations are validated by measurements at one of the measurement sites before and after rehabilitation of a deteriorated concrete pavement. Finally, the results are used to investigate the relation between indicators of road unevenness such as the ISO 8608 road class, the International Roughness Index, and the coefficient of evenness on one hand, and the dynamic vehicle response and level of ground-borne vibration on the other hand.

A Hybrid Inversion Technique for the Evaluation of Source, Path, and Site Effects Employing S-Wave Spectra for Subduction and Upper-Crustal Earthquakes in El Salvador

We propose a hybrid inversion analysis (hia) technique aimed at incorporating earthquakes from different seismogenic sources in one single inversion scheme. The application of this technique provides estimations of the source, path, and site effects at 23 strong-motion stations in El Salvador, Central America. The strong-motion dataset comprises 404 triaxial accelerograms corresponding to 63 subduction and upper-crustal earthquakes with M S magnitudes between 3.0 and 7.8. Application of the hia technique reveals: (1) good matching of the estimated source spectra with those derived from the ω 2 point source model; (2) rapid and low attenuation patterns characterizing the upper-crustal volcanic belt and subduction zone, respectively; and (3) soil transfer functions characterized by amplification ratios larger than those derived from spectral ratio techniques by a factor of two. Reference- site-dependent techniques yield similar soil transfer functions at all stations, whereas the horizontal-to-vertical spectral ratio technique yields similar results at sites characterized by clearly predominant peaks.

The experimental validation of a numerical model for the prediction of railway induced vibrations

This paper presents the experimental validation of a numerical model for the prediction of train induced vibrations. The model fully accounts for the dynamic interaction between the train, the track and the soil. The track geometry is assumed to be invariant with respect to the longitudinal direction, which allows for an efficient solution of the dynamic track–soil interaction problem in the frequency–wavenumber domain. The model is validated by means of several experiments that have been performed at the occasion of the homologation tests of the new HST track on the line L2 between Brussels and Köln. A first set of experiments is used to determine the dynamic soil and track characteristics. In a second set of experiments, the soil transfer functions, the track–soil transfer functions and the track and free field vibrations during the passage of a Thalys high speed train have been measured. These results are used for a step-wise validation of the numerical model that is based on the identified model parameters and allows to study the propagation of errors in the prediction model.

Geotechnical Site Characterisation in the Umbria-Marche Area and Evaluation of Earthquake Site-Response

In this research a site classification is proposed for the Umbria-Marche area (central Italy), based on geotechnical and geomorphological criteria. Two empirical techniques to evaluate site effects are used, namely the generalised spectral inversion, and the horizontal to vertical spectral ratio. The soil transfer functions obtained by the two techniques are compared in order to capture the features common to each class and verify the accuracy of the classification. We used strong ground motions recorded during the Umbria-Marche seismic sequence (September 1997-May 1998) and we selected 25 sites that were classified into four groups. The results of the empirical techniques have also been tested using theoretical 1-D or 2-D methods that are commonly used to simulate linear soil behaviour. The results, expressed in terms of amplitude transfer functions, are shown according to each soil class and confirm the consistency of the site characterisation. The empirical techniques are efficient in detecting the fundamental frequency of vibration but seldom the higher harmonics. Conversely, the peak amplitude of the transfer functions is not consistently determined, especially for sites located in deep sedimentary basins, where 2-D effects occur and simplified methods, such as the horizontal to vertical spectral ratios (HVSR) or 1-D theoretical models frequently fail. Significant amplifications are also found for 2-D rock structures such as rock crests or cliffs.

The effects of torsion and motion coupling in site response estimation

AbstractSoil amplification characteristics are investigated using data from the Chibaken‐Toho‐Oki earthquake and its aftershocks recorded at Chiba dense array in Japan. The frequency‐dependent amplification function of soil is calculated using uphole‐to‐downhole spectral ratio analysis, considering the horizontal components of shear wave. The identified spectral ratios consistently demonstrate the splitting of peaks in their resonance frequencies and low amplification values in comparison with a 1D model. The torsional behaviour and horizontal ground motion coupling are clarified as the reasons for these phenomena at the site. To prove the hypothesis, the torsional motion is directly evaluated using the data of the horizontal dense array in different depths at the site. The comparison between Fourier spectra of torsional motion and identified transfer functions reveals the peaks at the same frequencies. The wave equation including torsion and horizontal motion coupling is introduced and solved for the layered media by applying wave propagation theory. Using the developed model, the effects of torsional motion with horizontal motion coupling on soil transfer function are numerically examined. Splitting and low amplification at resonance frequencies are confirmed by the results of numerical analysis. Furthermore, the ground motion in two horizontal directions at the site is simulated using site geotechnical specification and optimizing the model parameters. The simulated and recorded motions demonstrate good agreement that is used to validate the hypothesis. In addition, the spectral density of torsional ground motions are compared with the calculated one and found to be well predicted by the model. Finally, the results are used to explain the overestimation of damping in back‐calculation of dynamic soil properties using vertical array data in small strain level. Copyright © 2003 John Wiley &amp; Sons, Ltd.

P-wave Amplification by Near-Surface Deposits at Different Excitation Levels

Possible nonlinearity in the response of sedimentary layers to incident P waves is studied using the strong-motion data from a vertical array in Taiwan at the site where a significant nonlinear response to S waves had been found. Soil transfer functions are analyzed at different excitation levels with a maximum vertical acceleration at surface reaching -0.1 g, corresponding to the compressional strain of 7 × 10 -5. Weak-motion and strong-motion transfer functions are compared. No effects of reduced amplification or change in resonance frequencies with increasing strain level were observed, suggesting that the response remained linear in the range of strain under consideration.