Surface Wave Survey Research Articles

Frequency–Wavenumber (FK)-Based Data Selection in High-Frequency Passive Surface Wave Survey

Passive surface wave methods have gained much attention from geophysical and civil engineering communities because of the limited application of traditional seismic surveys in highly populated urban areas. Considering that they can provide high-frequency phase velocity information up to several tens of Hz, the active surface wave survey would be omitted and the amount of field work could be dramatically reduced. However, the measured dispersion energy image in the passive surface wave survey would usually be polluted by a type of “crossed” artifacts at high frequencies. It is common in the bidirectional noise distribution case with a linear receiver array deployed along roads or railways. We review several frequently used passive surface wave methods and derive the underlying physics for the existence of the “crossed” artifacts. We prove that the “crossed” artifacts would cross the true surface wave energy at fixed points in the f–v domain and propose a FK-based data selection technique to attenuate the artifacts in order to retrieve the high-frequency information. Numerical tests further demonstrate the existence of the “crossed” artifacts and indicate that the well-known wave field separation method, FK filter, does not work for the selection of directional noise data. Real-world applications manifest the feasibility of the proposed FK-based technique to improve passive surface wave methods by a priori data selection. Finally, we discuss the applicability of our approach.

CONTRIBUCIÓN DE LAS FRECUENCIAS CARACTERÍSTICAS AL PERIODO DE VIBRACIÓN DOMINANTE EN LA CIUDAD DE QUERÉTARO, MÉXICO

En este trabajo se presenta la metodología desarrollada para evaluar la contribución de la frecuencia característica de cada estrato al período fundamental de vibración a partir de la inversión de las curvas de dispersión aparente obtenidas del levantamiento en campo de ondas superficiales con fuente activa, sin importar la velocidad de cada capa. El cálculo del período fundamental se realizó con el procedimiento simplificado de un medio estratificado lineal desarrollado por Dobry et al. (1976). Como referencia para la clasificación por clases o categorías de velocidades se utilizó el elaborado por el International Building Code (IBC, 2009) y modificado para los materiales del subsuelo de la Ciudad de Querétaro. Las unidades geológicas principales se agruparon en tres secuencias estratigráficas: la Rocosa que abarca las mesetas y elevaciones topográficas que rodean el valle, la de Ladera que es la zona de pendiente variable constituida por depósitos volcánicos y sedimentarios (aluviales), y la secuencia de Planicie que comprende depósitos estratificados del tipo lacustre, fluvial y volcánico. A partir del análisis de los perfiles de velocidades de ondas de corte se observó que existen estratos con velocidades bajas confinados por otros de alta velocidad; lo que indica la presencia de estratos de baja rigidez a profundidades variables. En la zona rocosa el período fundamental de vibración es corto (menor que 0.1 s), mientras que en los depósitos de la planicie es más largos (mayor que 0.3 s). En la zona de ladera el período es relativamente largo (variable entre 0.1 s a 0.3 s) posiblemente debido a un efecto topográfico. Los resultados obtenidos muestran que la metodología propuesta para evaluar el período dominante a partir de la integración de las frecuencias características obtenidas con ondas superficiales permite estimar los espesores y velocidades de corte de cada estrato, el periodo fundamental de vibración de cada secuencia estratigráfica y finalmente, sus espectros de sitio.

S-wave reflection and surface wave surveys in liquefaction affected areas: a case study of the Hinode area, Itako, Ibaraki, Japan

Property damage results from liquefaction that occurs easily in soft sandy layers. Moreover, liquefaction damage tends to be more serious at locations where earthquake ground motions are locally amplified. It is commonly understood that ground stiffness is correlated with S-wave velocity (Vs); in addition, the structure of the local subsurface is important for predicting local earthquake ground motion. Surface wave and S-wave reflection surveys are efficient, non-destructive techniques used to obtain two-dimensional S-wave velocity distributions and to map subsurface structures. In this study, we performed surface wave and S-wave reflection surveys to investigate the Hinode area of Itako, Ibaraki, Japan. This area suffered serious liquefaction damage during the Great Eastern Japan Earthquake of 2011. Using subsurface boundaries imaged by the reflection surveys and the Vs structures obtained by surface wave analyses, it is possible to extrapolate geological and hydraulic information obtained by boring and cone penetration tests (CPTs). The combined information was used to delineate the layer in which liquefaction occurred, identified as an artificial layer of sandy dredged material, formed after 1970. The results of this study confirmed the effectiveness and applicability of geophysical surveys to the evaluation of the liquefaction potential. These methods enable us to predict the spatial distribution of liquefiable soils for future large earthquakes.

平成23年（2011年）東北地方太平洋沖地震による液状化発生領域での表面波探査 ―千葉県香取市利根川北岸地区の例―

2011年3月11日に平成23年（2011年）東北地方太平洋沖地震が発生し，多くの被害が発生した。東京湾岸や利根川下流域では広範囲にわたって，液状化の被害を受けた。本研究では，利根川下流域にあたる千葉県香取市の利根川北岸地域で表面波探査を実施し，地下約30 mまでのS波速度（Vs）構造を求めた。その結果，調査領域の地下は，比較的高速度のVsを持つ砂質表層，低速度のシルト質層，高速度の砂質基盤層の三層に区分されることがわかった。

Surface wave surveying for near-surface site characterization in the East San Francisco Bay Area, California

Seismic surface wave methods are effective tools for estimating S-wave velocity in urban areas for near-surface site characterization and geologic hazard assessment. A surface wave survey can provide quantitative site-specific measurement of physical properties needed for the design of earthquake-resistant structures. We successfully used a combined active and passive seismic surface wave method to estimate the S-wave velocity in the upper 30 m at sites with a range of geologic conditions. At five of the six sites, multichannel analysis of surface waves (MASW) and microtremor array method (MAM) methods were used. The MAM method could not be used at one site due to insufficient ambient noise. Data from the active method (MASW) contained higher frequencies that contributed to higher resolution of the near-surface zone, whereas passive data (MAM) contained lower frequencies that provided deeper penetration. Phase velocities from the two methods were in good agreement in the frequency range where they overlapped. Surface wave dispersion curves from the two methods were used to prepare an initial velocity model, and a nonlinear inversion was performed to obtain an improved velocity-depth profile. The use of a multimethod data set provided greater confidence in velocity measurements. The six sites of this study may be classified as belonging to two main groups based on S-wave velocities and geologic materials. Two sites are located in the East Bay Hills on Mesozoic bedrock, and four sites are located on Holocene sedimentary units. The highest [Formula: see text] was [Formula: see text] (class C), at a site with fractured and weathered bedrock exposed in a geotechnical trench at 1–2 m depth. The four sites on Holocene sedimentary units have [Formula: see text] values ranging from 207 to [Formula: see text] (class D).

Aged embankment imaging and assessment using surface waves

Rapid, non-intrusive surface wave surveys provide depth profiles from which ground models can be generated for use in earthwork condition assessment. Stiffness throughout earthworks controls the behaviour under static and dynamic loads, and characterising heterogeneity is of interest in relation to the stability of engineered backfill and life-cycle deterioration in aged utility and transportation infrastructure. Continuous surface wave methods were used to identify interfaces between fine- and coarse-grained fill in an end-tipped embankment along the Great Central Railway in Nottinghamshire, UK. Multichannel analysis of surface wave (MASW) methods were used to characterise subsurface voiding in a canal embankment along the Knottingley and Goole canal near Eggborough, Yorkshire. MASW methods are currently being used to study extreme weather impacts on the stability of a high-plasticity clay embankment along the Gloucestershire–Warwickshire railway near Laverton. Optimal results were obtained using equipment capable of generating and detecting over wide frequency ranges.

A Low-Cost Energy-Efficient Cableless Geophone Unit for Passive Surface Wave Surveys.

The passive surface wave survey is a practical, non-invasive seismic exploration method that has increasingly been used in geotechnical engineering. However, in situ deployment of traditional wired geophones is labor intensive for a dense sensor array. Alternatively, stand-alone seismometers can be used, but they are bulky, heavy, and expensive because they are usually designed for long-term monitoring. To better facilitate field applications of the passive surface wave survey, a low-cost energy-efficient geophone system was developed in this study. The hardware design is presented in this paper. To validate the system’s functionality, both laboratory and field experiments were conducted. The unique feature of this newly-developed cableless geophone system allows for rapid field applications of the passive surface wave survey with dense array measurements.

Site-specific ground motion simulation and seismic response analysis for microzonation of Nanded City, India

We study strong ground motion characteristics and ground response analysis of different sites in Nanded City, India. Synthetic strong ground motion records are obtained for two scenario earthquakes of magnitude M 5.2 and M 6.8 in southern Peninsular India using the finite fault model. Shear-wave velocity averaged over top 30 m of the soil is obtained from multichannel analysis of surface wave survey at 60 sites at depths of 20–50 m below the ground surface. The sites in different parts of the city are characterized by peak ground acceleration (PGA) at the surface and bedrock level, 5 % damped response spectra at the ground surface and the amplification factor defined as the ratio of ground motion at the surface to that at the bedrock. The area east to the lineament is characterized by low V S30 values (<200 m/s), probably associated with Godavari River basin sediments with alluvial deposits, composed of brown clay with intercalated bands of sand and gravel. A relatively high PGA value at the surface of about 0.24 g for the M 5.2 target event and hence high ground motion amplification indicative of major damage are observed at sites E-NE to the lineament in the area that are associated with the top soil column consisting of unconsolidated river basin sediments with very low V S30 values (<200 m/s). The amplification factor for the city ranges from 3 to 8 for the highest target event of magnitude M 6.8. There is a strong lateral variation in PGA values at the surface for the part of the city lying to the east of the lineament and parallel to its trend, where a relatively high amplification factor of 6–8 is found at a dominant frequency of 1.5–2.5 Hz, which can be considered as a significant zone of amplification and hence areas with high seismic hazard. The site-specific response spectra show that the peak of spectral acceleration for different sites occurs around 3 Hz. There is a large spatial variation of spectral acceleration at any given frequency for the city. For example, site nos. 9 and 50 are characterized by a peak in spectral acceleration of 0.55 and 0.9 g, respectively, at 3 Hz frequency.

Application of the Surface Wave Survey Method on Multi-Scale Engineering Problems: Laboratory and Field Testing Case Studies

Abstract The geometric dispersion of surface waves offers the feature to infer the properties of a medium. The surface wave survey method is under continuous evolution and its applications include the noninvasive characterization of a medium at a small scale and the earthquake geotechnical survey at a large scale. Despite the significant difference in scales, these applications generally utilize the propagation of the surface waves along the boundary of a layered medium. This paper discusses standard steps involved in surface wave surveys. Two application case studies are conducted and presented in detail. In the small scale laboratory application case, a nondestructive testing (NDT) methodology is proposed for the coating investigation using laser interferometric measurements of surface waves. In the large scale field application, an accelerometer-based passive surface wave survey is designed for earthquake geotechnical engineering site characterization. Finally, recommendations for practical application of surface waves in multi-scale engineering problems are presented.

Physical modelling of a surface-wave survey over a laterally varying granular medium with property contrasts and velocity gradients

Laboratory experiments using laser-based ultrasonic techniques can be used to simulate seismic surveys on highly controlled small-scale physical models of the subsurface. Most of the time, such models consist in assemblies of homogeneous and consolidated materials. To enable the physical modelling of unconsolidated, heterogeneous and porous media, the use of granular materials is suggested here. We describe a simple technique to build a two-layer physical model characterized by lateral variations, strong property contrasts and velocity gradients. We use this model to address the efficiency of an innovative surface-wave processing technique developed to retrieve 2-D structures from a limited number of receivers. A step by step inversion procedure of the extracted dispersion curves yields accurate results so that the 2-D structure of the physical model is satisfactorily reconstructed. The velocity gradients within each layer are accurately retrieved as well, confirming current theoretical and experimental studies regarding guided surface acoustic modes in unconsolidated granular media.

MASW for geotechnical site investigation

Multichannel anaylsis of surface waves (MASW) is a seismic surface-wave technique developed specifically for near-surface applications at depths usually shallower than a few tens of meters (Park et al., 1999). Since its introduction in the late 1990s, use of the technique has rapidly increased for two reasons: (1) it provides the shear-wave velocity (VS) of ground materials, which is one of the most important geotechnical parameters in civil engineering, and (2) it is easier to use than other common seismic approaches (e.g., refraction, reflection, and surface-wave surveys).

電気探査・表面波探査によるビーチロックの地下構造&lt;br/&gt;─沖縄県名護市屋我地島沿岸地点での適用例─

沿岸域で適用可能な自己修復能力を持つ人工岩盤に関する研究は，環境に負荷を与えず低コストで海岸堤防を建設する上で重要と考えられ，自然材料（微生物，砂，貝殻，サンゴ片，海藻など）を用いて厳しい気象条件に耐えうる強度の人工岩盤を比較的短期間で形成させることを目標としている。その一つのモデルとして，熱帯・亜熱帯地域のサンゴ礁沿岸域に存在するビーチロックが着目されているが，その地下構造を明らかにした調査事例はほとんどない。そこで，沖縄県内に数多く分布が確認されているビーチロックの地下構造を地表面から非破壊で明らかにすることを目的に，電気探査法および表面波探査法を行った。また，ビーチロック試料を用いた室内試験によりその物理特性を計測した。その結果，ビーチロックはその下部にある未固結の砂層より明らかに比抵抗と弾性波速度が大きく，その厚さは最大1m程度で海側に近いほど厚さは増加する傾向があることが分かった。

Seismic Imaging of a Leachate-Recirculation Landfill: Spatial Changes in Dynamic Properties of Municipal Solid Waste

Leachate-recirculation landfills enhance waste degradation through percolation of leachate inside the waste mass. In situ monitoring of moisture distribution and changes in mechanical properties (stiffness) of municipal solid waste (MSW) is needed to optimize the safe and effective operation of these types of landfills. Geophysical methods, such as electrical-resistivity tomography, have effectively monitored moisture distribution during and after leachate injection. This study investigates seismic surveys to capture the changes in mechanical properties [shear modulus (via shear-wave velocity) and Poisson’s ratio] of MSW to infer the extent of degradation and provide dynamic properties needed for seismic stability evaluation. To achieve this goal, a series of seismic surveys were performed at the Veolia ES Orchard Hills landfill, 15 km south of Rockford, Illinois, to image seismic velocity structure and the Poisson’s ratio of a recirculation cell, compared with an adjacent newer landfill cell without leachate recirculation. Seismic data were collected using fan shot direct P-wave (compressional wave) surveys and S-wave (shear wave) surveys, conventional P-wave refraction, and the multichannel analysis of surface waves (MASW) method. The fan shot surveys employed a sledgehammer source on one side of the landfill and geophones on the opposite side, thus exploiting the landfill’s topography and geometry to image waste to a depth of approximately 10 m. P-wave-velocity tomographic models and S-wave-velocity tomographic models from these direct-wave (through-pile) raypaths indicate a dramatic velocity increase below 5 m depth, perhaps indicating consolidation and compaction of the waste material. The ratio in P-wave to S-wave velocity ranges from 1.8 to 3.7, with an average of approximately 2.7, and Poisson’s ratio ranges from 0.29 to 0.46, with an average value of 0.42 (standard deviation 0.024). In the upper 5 m S-wave velocity (∼150–170 m/s) is higher at the recirculation cell than in newer portions of the landfill consisting of uncompacted waste (∼110–120 m/s), as derived from analysis of surface waves. The landfill cap, which is present over the recirculation cell, but not over the new waste, may be at least partly responsible for this difference. S-wave velocities are very similar below 5 m depth, whereas P-wave velocity (from seismic-refraction profiling) indicates a slight decrease in velocity between the leachate-recirculation cell and newer portions of the landfill. The refraction and surface wave surveys, however, were depth-limited (less than 8–9 m), compared with the fan shots. Overall, this study showed that seismic surveys have the potential to monitor spatial and temporal variation of dynamic properties of MSW.

A performance-based framework for assessing liquefaction potential based on CPT data

This article describes a new performance-based approach for evaluating the return period of seismic soil liquefaction based on standard penetration test (SPT) and cone penetration test (CPT) data. The conventional liquefaction evaluation methods consider a single acceleration level and magnitude and these approaches fail to take into account the uncertainty in earthquake loading. The seismic hazard analysis based on the probabilistic method clearly shows that a particular acceleration value is being contributed by different magnitudes with varying probability. In the new method presented in this article, the entire range of ground shaking and the entire range of earthquake magnitude are considered and the liquefaction return period is evaluated based on the SPT and CPT data. This article explains the performance-based methodology for the liquefaction analysis – starting from probabilistic seismic hazard analysis (PSHA) for the evaluation of seismic hazard and the performance-based method to evaluate the liquefaction return period. A case study has been done for Bangalore, India, based on SPT data and converted CPT values. The comparison of results obtained from both the methods have been presented. In an area of 220 km2 in Bangalore city, the site class was assessed based on large number of borehole data and 58 Multi-channel analysis of surface wave survey. Using the site class and peak acceleration at rock depth from PSHA, the peak ground acceleration at the ground surface was estimated using probabilistic approach. The liquefaction analysis was done based on 450 borehole data obtained in the study area. The results of CPT match well with the results obtained from similar analysis with SPT data.

Comparison of surface wave techniques to estimate shear wave velocity in a sand and gravel sequence: Holme Pierrepont, Nottingham, UK

This study evaluated the application of surface wave methods to aggregate variability and thickness determinations. We compared the results of field assessments of sand and gravel sequences using three surface wave survey approaches. The first was a seismic refraction approach, the second, a continuous surface wave (CSW) survey approach, and the third adopted a multi-channel analysis of surface waves (MASW) technique to the original refraction field set-up and records. The sand and gravel sequences were highly heterogeneous and the shear wave profiles were not normally dispersive (i.e. did not exhibit a monotonic increase in velocity with depth), which had a significant effect upon the performance of the three field approaches. Both CSW and MASW approaches provided information over a broad spectrum from which velocity–depth profiles were produced, but the upper frequency of operation was limited in both methods because of poorer signal quality at higher frequencies. Shear wave velocity profiles obtained using vertically vibrating sources during CSW surveys were different from profiles obtained using a horizontally polarized source in the refraction survey. This was attributed to different propagation paths and modes of propagation, which were illustrated via additional tomographic inversion of the refraction travel times but could also be attributed to data inversion methods. Probing using an ultra-lightweight cone penetrometer, continuous reflection profiling using ground-penetrating radar, and also an active extraction programme at the field site provided the opportunity to directly observe the subsurface geology and verify field results. Within the sand and gravel sequence, high-velocity layers were associated with matrix-supported coarse gravel lenses, some of which were weakly cemented. Localized high- and low-velocity zones within the underlying bedrock were interpreted as being related to lithostratigraphic heterogeneity and the development of an upper, weathered zone.

Pitfalls in interpretation of shallow seismic data

High-resolution shallow seismic methods are the most widely used geophysical methods in near surface characterization. However, in many cases interpreting the seismic images can be misleading. In this article, we present three case studies where results from P-wave seismic reflection, SH-wave seismic reflection, and multi-channel analysis of surface wave (MASW) surveys were incorrectly interpreted because of inadequate constraints on either the surveyed sites surface or subsurface conditions. A P-wave reflection survey feature was first interpreted as a shallow fault zone but it was later determined to result from a high level of background noise as the acquisition passed through a road intersection. A SH-wave seismic reflection survey feature was interpreted to be a reverse dip-slip fault but targeted drilling showed it was deep local erosion into the bedrock surface. Finally, in an MASW survey, a steeply dipping feature was first interpreted as a bedrock valley. However, later exploratory drilling showed the feature to be a shallow layer of very soft lake sediment that severely damped most of the applied surface wave frequency band. Although initial interpretations were incorrect, they stimulated discussions among geophysicists and geologists and underscored the need for meaningful cooperation and discourse between the scientists before, during, and after geophysical data acquisition.

Amplification based on shear wave velocity for seismic zonation: comparison of empirical relations and site response results for shallow engineering bedrock sites

Amplification based on empirical relations is widely used for seismic microzonation of urban centers. Amplifications are used to represent the site effects of a particular soil column. Many empirical correlations are available to estimate the amplification of seismic waves. These correlations are based on the ratio of shear wave velocity of foundation/rock to soil velocity or 30 m equivalent shear wave velocity (<TEX>$Vs^{30}$</TEX>) and are developed considering deep soil data. The aim of this work is to examine the applicability of available amplification relations in the literature for shallow engineering bedrock sites by carrying out site response studies. Shear wave velocity of thirteen sites having shallow engineering bedrock have been selected for the study. In these locations, the depth of engineering bedrock (> 760 <TEX>${\pm}$</TEX> 60 m/s) is matched with the drilled bore hole. Shear wave velocity (SWV) has been measured using Multichannel Analysis of Surface Wave survey. These sites are classified according to the National Earthquake Hazards Reduction Program (NEHRP) classification system. Amplifications for an earthquake are arrived for these sites using empirical relations and measured SWV data. Site response analysis has been carried out in SHAKE using SWV and using synthetic and real earthquake data. Amplification from site response analysis and empirical relations are compared. Study shows that the amplification arrived using empirical relations does not match with the site response amplification. Site response amplification is much more than empirical values for same shear wave velocity.

Surface wave surveys for seismic site characterization of accelerometric stations in ITACA

This paper reports on site characterization for a set of accelerometric stations of the RAN (Italian accelerometric network) with specific attention to the shear wave velocity profile. The latter is indeed of primary importance for the usability of the accelerometric database. Surface wave analysis has been chosen as the primary investigation method since it offers the possibility of reaching the required accuracy with reasonable costs. A range of different techniques, both of the active-source and passive-source types, has been adopted to cope with the objectives of the characterization in relation to specific geological settings. Quality assessment of experimental data has been implemented to check the consistency of the measurements also with respect to the fundamental hypotheses of the method. Strategies to improve the reliability and robustness of the surface wave data inversion were exploited in order to mitigate problems arising from solution non-uniqueness and influence of higher modes in the propagation. Comparisons with independent borehole tests, available at some specific sites, confirm the reliability of the results. Although the research program covered only a subset of the network, the obtained results show the importance of specific experimental investigations aimed at estimating the shear wave velocity profile. Indeed the results lead to a re-classification of several sites with respect to the preliminary classification based on surface geology. Within this context, four selected case histories are reported in the present paper.

Application of Surface-Wave Methods for Seismic Site Characterization

Surface-wave dispersion analysis is widely used in geophysics to infer a shear wave velocity model of the subsoil for a wide variety of applications. A shear-wave velocity model is obtained from the solution of an inverse problem based on the surface wave dispersive propagation in vertically heterogeneous media. The analysis can be based either on active source measurements or on seismic noise recordings. This paper discusses the most typical choices for collection and interpretation of experimental data, providing a state of the art on the different steps involved in surface wave surveys. In particular, the different strategies for processing experimental data and to solve the inverse problem are presented, along with their advantages and disadvantages. Also, some issues related to the characteristics of passive surface wave data and their use in H/V spectral ratio technique are discussed as additional information to be used independently or in conjunction with dispersion analysis. Finally, some recommendations for the use of surface wave methods are presented, while also outlining future trends in the research of this topic.

Influence of uneven trace spacing on Rayleigh wave dispersion

Rayleigh wave dispersion signals are significant to underground investigation. Traditionally, uniformed trace spacing is employed in surface wave surveys. In some cases, however, uneven trace spacing is often encountered because of the limitations of the site condition. In order to study the influence of uneven trace spacing on the dispersion data construction of Rayleigh waves, data acquisition is performed based on a 2.5D field layout with a linear array of geophones fixed and a mobile source. The observation direction controls the trace spacing of the measurement. The final results demonstrate that the trace nonuniformity has significant influence on the Rayleigh wave dispersion feature constructed. When the observation angle is over 45°, the dispersion image will be too distorted to extract dispersion data correctly.