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1
Mi, Binbin, Jianghai Xia, Chao Shen, Limin Wang, Yue Hu, and Feng Cheng. "Horizontal resolution of multichannel analysis of surface waves." GEOPHYSICS 82, no. 3 (May 1, 2017): EN51—EN66. http://dx.doi.org/10.1190/geo2016-0202.1.
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The multichannel analysis of surface wave (MASW) method has been effectively and widely used to determine near-surface shear-wave velocity. Horizontal resolution of the MASW method represents the minimum horizontal length of recognizable geologic anomalous bodies on a pseudo-2D S-wave velocity [Formula: see text] section. Accurately assessing the achievable lateral resolution is one of the main issues in lateral variation reconstruction using the MASW method. It is difficult to quantitatively estimate the horizontal resolution of the MASW method because of the many influencing factors, such as parameters of the observation system, the depth of an anomalous body, and the velocity contrast between the anomalous body and the surrounding rocks. We first analyzed the horizontal resolution of the MASW method based on numerical simulation experiments. According to different influencing factors of the horizontal resolution, we established different laterally heterogeneous models and observation systems and then simulated several synthetic multichannel records with a finite-difference method along a linear survey line using the roll-along acquisition mode. After the extraction of dispersion curves of Rayleigh waves and inversion for S-wave velocity profiles for each synthetic shot gather, a pseudo-2D S-wave velocity section can be generated by aligning the 1D S-wave velocity models. Ultimately, we evaluated the horizontal resolution capability of the MASW method on pseudo-2D [Formula: see text] maps. Our numerical investigation results and field data analysis indicate that [Formula: see text] values on the maps are not the same as the true [Formula: see text] values for structures whose lateral dimension is shorter than a receiver spread length and that anomalous bodies, which are larger and have high velocity contrast, are easier to distinguish on [Formula: see text] maps with a shorter receiver spread length. The horizontal resolution decreases with the increasing depth and is approximately one-half of the shortest Rayleigh wavelength that can penetrate to the depth.
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Le Ngal, Nwai, Subagyo Pramumijoyo, Iman Satyarno, Kirbani Sri Brotopuspito, Junji Kiyono, and Eddy Hartantyo. "Multi-channel analysis of surface wave method for geotechnical site characterization in Yogyakarta, Indonesia." E3S Web of Conferences 76 (2019): 03006. http://dx.doi.org/10.1051/e3sconf/20197603006.
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On May 27th 2006, Yogyakarta earthquake happened with 6.3 Mw. It was causing widespread destruction and loss of life and property. The average shear wave velocity to 30 m (Vs30) is useful parameter for classifying sites to predict their potential to amplify seismic shaking (Boore, 2004) [1]. Shear wave velocity is one of the most influential factors of the ground motion. The average shear wave velocity for the top 30 m of soil is referred to as Vs30. In this study, the Vs30 values were calculated by using multichannel analysis of surface waves (MASW) method. The Multichannel Analysis of Surface Waves (MASW) method was introduced by Park et al. (1999). Multi-channel Analysis of Surface Waves (MASW) is non-invasive method of estimating the shear-wave velocity profile. It utilizes the dispersive properties of Rayleigh waves for imaging the subsurface layers. MASW surveys can be divided into active and passive surveys. In active MASW method, surface waves can be easily generated by an impulsive source like a hammer, sledge hammer, weight drops, accelerated weight drops and explosive. Seismic measurements were carried out 44 locations in Yogyakarta province, in Indonesia. The dispersion data of the recorded Rayleigh waves were processed by using Seisimager software to obtain shear wave velocity profiles of the studied area. The average shear wave velocities of the soil obtained are ranging from 200 ms-1 to 988 ms-1, respectively.
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Nguyen, Ngan Nhat Kim, Luu Van Do, Van Thanh Nguyen, Trinh Phuc Tran, and Khuong Manh Vo. "Maximizing the energy of surface wave and diminishing the effect of lateral inhomogenousness in the multichannel analysis of the surface wave (MASW)." Science and Technology Development Journal - Natural Sciences 2, no. 5 (July 2, 2019): 105–12. http://dx.doi.org/10.32508/stdjns.v2i5.785.
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Multichannel analysis of surface wave (MASW) is one of the novel seismic methods in geophysic field in Vietnam. MASW is able to survey the stiffness of the soil environment under the ground via the shear-wave velocity VS by analyzing the spectral image of surface wave. We did the 1D MASW survey upon the borehole belonged to the residential development project at district 2, Ho Chi Minh city with fixed receiver system, different source orientations and different source offsets. The spectral images of surface wave were combined to maximize the surface wave’s energy on the spectral image of surface wave to minimize the effect of lateral inhomogenousness and near - far source offsets. The data points were chosen on the phase curve on spectral image of surface wave for the inversion process to define shear wave velocity VS. The VS from MASW was compared to the petrographic components and another seismic method (downhole). The relative difference of the obtained VS values between two methods was less than 10%. The change of VS in MASW was absolutely compatible to petrographic components in geological borehole, near surface filled soil layer (93 m/s), dark-gray silty layer (68–157 m/s), sandy clay layer (250–265 m/s) and lower clay layer (254–400 m/s).
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Ivanov, Julian, Richard D. Miller, Daniel Feigenbaum, Sarah L. C. Morton, Shelby L. Peterie, and Joseph B. Dunbar. "Revisiting levees in southern Texas using Love-wave multichannel analysis of surface waves with the high-resolution linear Radon transform." Interpretation 5, no. 3 (August 31, 2017): T287—T298. http://dx.doi.org/10.1190/int-2016-0044.1.
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Shear-wave velocities were estimated at a levee site by inverting Love waves using the multichannel analysis of surface waves (MASW) method augmented with the high-resolution linear Radon transform (HRLRT). The selected site was one of five levee sites in southern Texas chosen for the evaluation of several seismic data-analysis techniques readily available in 2004. The methods included P- and S-wave refraction tomography, Rayleigh- and Love-wave surface-wave analysis using MASW, and P- and S-wave cross-levee tomography. The results from the 2004 analysis revealed that although the P-wave methods provided reasonable and stable results, the S-wave methods produced surprisingly inconsistent shear-wave velocity [Formula: see text] estimates and trends compared with previous studies and borehole investigations. In addition, the Rayleigh-wave MASW method was nearly useless within the levee due to the sparsity of high frequencies in fundamental-mode surface waves and complexities associated with inverting higher modes. This prevented any reliable [Formula: see text] estimates for the levee core. Recent advances in methodology, such as the HRLRT for obtaining higher resolution dispersion-curve images with the MASW method and the use of Love-wave inversion routines specific to Love waves as part of the MASW method, provided the motivation to extend the 2004 original study by using horizontal-component seismic data for characterizing the geologic properties of levees. Contributions from the above-mentioned techniques were instrumental in obtaining [Formula: see text] estimates from within these levees that were very comparable with the measured borehole samples. A Love-wave approach can be a viable alternative to Rayleigh-wave MASW surveys at sites where complications associated with material or levee geometries inhibit reliable [Formula: see text] results from Rayleigh waves.
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Syamsuddin, Erfan, Sabrianto Aswad, Muhammad Alimuddin Hamzah Assegaf, Syamsurijal Rasimeng, Sakka Sakka, Syamsuddin Syamsuddin, Muhammad Nasri, and Mufly Fadla Syihab. "Seismic Site Classification Using the Multichannel Analysis of Surface Waves Method." POSITRON 12, no. 2 (November 30, 2022): 149. http://dx.doi.org/10.26418/positron.v12i2.53869.
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The soil has a variety of qualities that affect its ability to support the weight of a structure. One of these features is soil stiffness, which can be determined using the surface wave method to prevent soil collapse. Multichannel Analysis of Surface Waves (MASW) is one of the non-invasive methodologies used in this study to investigate subsurface structures in North Sumatra, Indonesia. This method utilizes the dispersion properties of Rayleigh waves, producing a dispersion curve to get the shear wave velocity (Vs) through inversion. The shear wave velocity can be used to examine the soil stiffness qualities. The dispersion curve explains the relationship between shear wave velocity and depth, which can subsequently be used as a site class parameter. This survey uses three lines with one shot for each line which uses thirty geophones. The seismic source used is a gun with the type M16.38 Cal. Each line consists of 30 geophones with a distance of 5 m. The entire track is 160 m long and lasts for 2048 seconds with a sampling rate of 0.00025 seconds. The average shear wave velocity measured at three measurements was 372.5 m/s on line P1, 347.1 m/s on line P2A, and 311.0 m/s on line P2B, respectively. Overall, the soil classification on the P1 line is class C, and the P2A and P2B lines are class D, which is suitable for development planning areas.
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Kurtuluş, Cengiz, Ibrahim Sertcelik, Fadime Sertçelik, Hamdullah Livaoğlu, and Cüneyt Şaş. "Investigation of Soil Characterization in Hatay Province in Turkey by Using Seismic Refraction, Multichannel Analysis of Surface Waves and Microtremor." Earth Sciences Research Journal 24, no. 4 (January 26, 2021): 473–84. http://dx.doi.org/10.15446/esrj.v24n4.79123.
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In this study, shallow seismic surveys, including seismic refraction, Multichannel Analysis of Surface Waves (MASW), Refraction Microtremor (ReMi), and Microtremor measurements were conducted to estimate site characterization at 26 strong-motion stations of AFAD (Disaster and Emergency Management Presidency) in the province of Hatay, situated in one of the most seismically active regions in southern Turkey. The Horizontal to vertical spectral ratio (HVSR) technique was applied, using smoothed Fourier spectra derived from a long duration series to determine dominant frequency values at different amplification levels. Shear wave velocity up to 30 m of the ground was detected with MASW analysis. In the ReMi analysis, up to 80 m was reached with a corresponding average of 650 m/s shear wave velocity. The shear wave velocities estimated by the MASW method up to 30 m were compared with those found by the ReMi method, and they were observed to be very compatible. The province of Hatay was classified according to Vs30 based NEHRP Provisions, Eurocode-8, the Turkish Building Earthquake Regulation (TBDY-2018), and Rodriguez-Marek et al. (2001). The shear-wave velocity (Vs30), Horizontal to Vertical ratio’s (H/V) peak amplitude, dominant period, and site class of each site were determined. The H/V peak amplitudes range between 1.9 and 7.6, while the predominant periods vary from 0.23 sec to 2.94sec in the study area. These results are investigated to explain the consistency of site classification schemes.
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Craig, Mitchell, and Koichi Hayashi. "Surface wave surveying for near-surface site characterization in the East San Francisco Bay Area, California." Interpretation 4, no. 4 (November 1, 2016): SQ59—SQ69. http://dx.doi.org/10.1190/int-2015-0227.1.
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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).
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Konstantaki, Laura Amalia, Ranajit Ghose, Deyan Draganov, Giovanni Diaferia, and Timo Heimovaara. "Characterization of a heterogeneous landfill using seismic and electrical resistivity data." GEOPHYSICS 80, no. 1 (January 1, 2015): EN13—EN25. http://dx.doi.org/10.1190/geo2014-0263.1.
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Understanding the processes occurring inside a landfill is important for improving the treatment of landfills. Irrigation and recirculation of leachate are widely used in landfill treatments. Increasing the efficiency of such treatments requires a detailed understanding of the flow inside the landfill. The flow depends largely on the heterogeneous distribution of density. It is, therefore, of great practical interest to determine the density distribution affecting the flow paths inside a landfill. Studies in the past have characterized landfill sites but have not led to high-resolution, detailed quantitative results. We performed an S-wave reflection survey, multichannel analysis of surface waves (MASW), and electrical resistivity survey to investigate the possibility of delineating the heterogeneity distribution in the body of a landfill. We found that the high-resolution S-wave reflection method offers the desired resolution. However, in the case of a very heterogeneous landfill and a high noise level, the processing of high-resolution, shallow reflection data required special care. In comparison, MASW gave the general trend of the changes inside the landfill, whereas the electrical resistivity (ER) survey provides useful clues for interpretation of seismic reflection data. We found that it is possible to localize fine-scale heterogeneities in the landfill using the S-wave reflection method using a high-frequency vibratory source. Using empirical relations specific to landfill sites, we then estimated the density distribution inside the landfill, along with the associated uncertainty considering different methods. The final interpretation was guided by supplementary information provided by MASW and ER tomography.
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Oloye, Oluwatobi, and Adekunle Adepelumi. "Characterization of the geological and geotechnical properties of soil using the surface wave approach." International Journal of Advanced Geosciences 3, no. 2 (July 22, 2015): 8. http://dx.doi.org/10.14419/ijag.v3i2.3963.
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<p>As part of the efforts to examine the elastic and engineering properties of the subsurface sequence at a proposed new power plant site in Edo State, a geophysical survey involving Multichannel Analysis of Surface Waves (MASW) was carried out. The MASW was adopted to determine the vertical and lateral variations in velocity beneath each seismic line. The MASW was carried out on two seismic lines each trending NE-SW. A geophone interval of 3 m was used, and the length of the seismic lines ranged from 60 – 90 m. The ES-3000 seismograph was used for the surface wave data acquisition and the Shear-Wave velocity structures of the area were obtained through the inversion of the acquired surface wave data. The one dimensional (1D) S-Wave velocity profiles along the lines were diagnostic of generally low velocity lithologies that suggest sand, clayey sand and sandy clay formations with relatively varying thicknesses. The subsurface layers delineated had shear-wave velocity values in the range of 63-400 m/s. They were classified using the NEHRP Seismic Site Classification, and all of them were in the range of stiff soil to soft clay soil. The bulk moduli (k) for these soils were in the range of 3.22-3.98 GPa. This depicts relatively low strength of the subsurface materials. The shear moduli (μ) values range from 7.15-7.43 MPa, which is indicative of low to moderate strength. The information provided in this study will aid the structural engineer or architect in foundation design of the proposed power plant. From the results of this study, it is concluded that although the subsurface layers are of relatively low strength, with the right intervention of the civil engineer, a suitable foundation can be designed for the gas plant.</p>
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Lewińska, Paulina, Rafał Matuła, and Artur Dyczko. "Integration of thermal digital 3D model and a MASW (Multichannel Analysis of Surface Wave) as a means of improving monitoring of spoil tip stability." E3S Web of Conferences 26 (2018): 00008. http://dx.doi.org/10.1051/e3sconf/20182600008.
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Spoil tips are anthropogenic terrain structures built of leftover (coal) mining materials. They consist mostly of slate and sandstone or mudstone but also include coal and highly explosive coal dust. Coal soil tip fires cause an irreversible degradation to the environment. Government organizations notice the potential problem of spoil tip hazard and are looking for ways of fast monitoring of their temperature and inside structure. In order to test new monitoring methods an experimental was performed in the area of spoil tip of Lubelski Węgiel „Bogdanka” S.A. A survey consisted of creating a 3D discreet thermal model. This was done in order to look for potential fire areas. MASW (Multichannel analysis of surface wave) was done in order to find potential voids within the body of a tip. Existing data was digitalized and a 3D model of object’s outside and inside was produced. This article provides results of this survey and informs about advantages of such an approach.
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Rahimi, Salman, Timothy Moody, Clinton Wood, Behdad Mofarraj Kouchaki, Michelle Barry, Khiem Tran, and Chris King. "Mapping Subsurface Conditions and Detecting Seepage Channels for an Embankment Dam Using Geophysical Methods: A Case Study of the Kinion Lake Dam." Journal of Environmental and Engineering Geophysics 24, no. 3 (September 2019): 373–86. http://dx.doi.org/10.2113/jeeg24.3.373.
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Capacitively-Coupled Resistivity (CCR), Electrical Resistivity Tomography (ERT), and seismic surface wave testing using Love and Rayleigh waves were performed on Kinion Lake Dam, an embankment dam that has historically experienced significant seepage and internal erosion issues. The goal of this study is to detect seepage locations in the embankment dam for remediation purposes and map bedrock location across the area using nondestructive geophysical measurements. Surveys were completed along the crest and downstream toe of the dam to map subsurface conditions with a focus on seepage detection. The seismic surface wave data were analyzed using two different methods: Multichannel Analysis of Surface Waves (MASW) and Full Waveform Inversion (FWI). Both MASW and FWI methods were shown to be capable of resolving the bedrock layer below the dam, but the FWI method, provided a higher resolution image of the subsurface conditions compared to MASW method. However, the MASW and FWI provided little guidance regarding the seepage path through the dam. The CCR and ERT surveys, on the other hand, were shown to be very valuable for seepage detection. The seepage paths of the embankment dam were detected by comparing the resistivity measurements acquired in a wet winter and a dry summer. These seepage regions correspond well with previous sinkholes observed in the pool area following a drought. Additionally, new drilling in the two regions which showed differences in resistivity indicated the areas contained highly fractured limestone with evidence of solution cavities. It seems that the highly fractured limestone becomes fully saturated during the wet season causing very low resistivity values for these layers in wet seasons, but it quickly loses the water during the dry season leading to a highly resistive material in dry seasons. Therefore, seasonal resistivity measurements can be considered as a useful method for locating potential weak zones of earthen hydraulic structures in a cost-effective and timely manner.
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Mollehuara-Canales, Raul, Nikita Afonin, Elena Kozlovskaya, Juha Lunkka, and Daniele Pedretti. "Leveraging active-source seismic data in mining tailings: Refraction and MASW analysis, elastic parameters, and hydrogeological conditions." Bulletin of the Geological Society of Finland 93, no. 2 (December 16, 2021): 104–27. http://dx.doi.org/10.17741/bgsf/93.2.002.
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We applied active-source seismic method for the interpretation of elastic parameters in tailings facilities which is essential for evaluating stability and seismic response. The methodology uses different analysis methods on the same dataset, i.e., conventional seismic refraction (SR) to determine compressional-wave velocity (Vp) and multichannel analysis of surface wave (MASW) to estimate shear-wave velocity (Vs). Seismic velocities in conjunction with tailings physics approach revealed interpretable data in terms of elastic parameters and hydrogeological conditions. The results determined the empirical linear relationships between Vp and Vs that are particular to an unconsolidated media such as tailings and showed that variability of hydrogeological conditions influences the elastic seismic response (Vp and Vs) and the elastic parameters. The analysis of the elastic parameters identified the state condition of the tailings at the time of the survey. The Bulk modulus K that relates the change in hydrostatic stress to the volumetric strain was predominant between 1.0−2.0 GPa. The Young’s modulus E in the tailings media was in the low range of 0.15−0.23 GPa. Poisson’s ratio values in all sections were in the upper limit in the range of 0.37−0.49, meaning that the tailings media is highly susceptible to transverse deformation under axial compression.
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Alonso-Pandavenes, Olegario, Daniela Bernal, Francisco Javier Torrijo, and Julio Garzón-Roca. "A Comparative Analysis for Defining the Sliding Surface and Internal Structure in an Active Landslide Using the HVSR Passive Geophysical Technique in Pujilí (Cotopaxi), Ecuador." Land 12, no. 5 (April 26, 2023): 961. http://dx.doi.org/10.3390/land12050961.
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Geophysical techniques were employed to analyze one of the landslides that affected the main access road to Pujilí (Ecuador). A passive seismic technique was utilized to test a total of 70 horizontal to vertical spectral ratio (HVSR) points, complemented by an active seismic-refraction profile and a multichannel analysis of surface waves (MASW) survey. The results from the active geophysical surveys facilitated the determination of the shear-wave-velocity value for the surface materials that were in motion. However, the HVSR provided the fundamental frequency fo and amplification Ao values of the ground. The Nakamura (1989) relationship was applied to obtain the thickness of the sediments over a compact material from the fundamental frequency of the terrain in a two-layer model. Additionally, constrained models of the shear-wave velocity (Vs) distribution in the landslide area, obtained from the active seismic surveys, were used to invert the ellipticity curves. The results from this inversion were compared with those obtained by applying the Nakamura equation. The landslide-rupture surface was delineated for each type of analysis, which verified the correlation and minimal differences between the results of the three proposed studies, thus validating the procedure. The directivity of the microtremor HVSR signals was also analyzed, demonstrating a relationship with the internal structure of the sliding material. Furthermore, the ability to slide concerning the Kg parameter (vulnerability index, Nakamura, 1989) was studied. The usefulness of the directivity analysis in defining the internal structures in landslide materials and in determining the areas with the most significant instability was demonstrated. Overall, the HVSR is considered valuable when conducting early landslide studies and is helpful in determining the rupture plane while remaining a simple, fast, and economical technique.
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Daryono, Lutfian R., Kazunori Nakashima, Satoru Kawasaki, Koichi Suzuki, Imam Suyanto, and Arief Rahmadi. "Investigation of Natural Beachrock and Physical–Mechanical Comparison with Artificial Beachrock Induced by MICP as a Protective Measure against Beach Erosion at Yogyakarta, Indonesia." Geosciences 10, no. 4 (April 15, 2020): 143. http://dx.doi.org/10.3390/geosciences10040143.
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Typically, the mitigation of coastal erosion is achieved by amending surface conditions using materials, such as concrete. The objective of this study is to evaluate the feasibility of constructing artificial beachrocks using natural materials (e.g., microbes, sand, shell, pieces of coral, and seaweed, etc.) within a short time, and to propose the method as a novel strategy for coastal protection. Initially, a survey on resistivity and a multichannel analysis of seismic waves (MASW) were conducted along the coastal lines to characterize and elucidate the subsurface structure of existing beachrocks in the Southeast Yogyakarta coastal area, Krakal–Sadranan beach, Indonesia. The field survey on natural beachrocks suggested that both resistivity and shear wave velocity were higher in the deeper deposits compared to the underlying unconsolidated sand layer within a depth of approximately 1.5 m and covering an area of 210.496 m2 for the α-section and 76.936 m2 for the β-section of beachrock deposit. The results of the sand solidification test in the laboratory showed that treated sand achieved unconfined compressive strength of up to around 6 MPa, determined after a treatment period of 14 days under optimum conditions.
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Alexopoulos, John D., Spyridon Dilalos, Nicholas Voulgaris, Vasileios Gkosios, Ioannis-Konstantinos Giannopoulos, Vasilis Kapetanidis, and George Kaviris. "The Contribution of Near-Surface Geophysics for the Site Characterization of Seismological Stations." Applied Sciences 13, no. 8 (April 14, 2023): 4932. http://dx.doi.org/10.3390/app13084932.
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The Athenet network is the network of the Seismological Laboratory of the National and Kapodistrian University of Athens. We present the geophysical investigation that has been carried out at six seismological stations of the Athenet network for their site characterization. More specifically, at the location of each seismological station, four geophysical methods have been carried out: Seismic Refraction Tomography (SRT), Multichannel Analysis of Surface Waves (MASW), the Horizontal to Vertical Spectral Ratio (HVSR) technique, and Electrical Resistivity Tomography (ERT). The applied geophysical survey provided important information regarding the site characterization at the selected seismological stations, including key parameters such as the fundamental frequency fo, the shear-wave velocity VS, the average shear-wave velocity for the upper 30 m depth (VS30), the seismic bedrock depth, the soil type, and the subsurface geology. Moreover, selected elastic moduli (Poisson’s ratio, shear, bulk, and Young moduli) have been calculated. The site characterization information contributes to the determination of the amplification factors for each site that can lead to more accurate calculation of Peak Ground Acceleration (PGA) or Peak Ground Velocity (PGV) and, therefore, trustworthy Probabilistic and Stochastic Seismic Hazard Assessments. The derived fundamental frequency for the seismological stations of VILL, LOUT, THAL, and EPID have been determined to be equal to 10.4, 2.7, 1.4, and 7.1 Hz and their amplification factors to be 1.9, 3.1, 1.7, and 2.6, respectively. For stations MDRA and ATAL, these parameters could not be determined.
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Matuła, Rafał, and Paulina Lewińska. "Geodetic survey as a means of improving fast MASW (Multichannel Analysis Of Surface Waves) profiling in difficult terrain/land conditions." E3S Web of Conferences 26 (2018): 00007. http://dx.doi.org/10.1051/e3sconf/20182600007.
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This paper revolves around newly designed and constructed system that can make 2D seismic measurement in natural, subsoil conditions and role of land survey in obtaining accurate results and linking them to 3D surface maps. A new type of land streamer, designed for shallow subsurface exploration is described in this paper. In land seismic data acquisition methods a vehicle tows a line of seismic cable, lying on construction called streamer. The measurements of points and shots are taken while the line is stationary, arbitrary placed on seismic profile. Exposed land streamer consists of 24 innovatory gimballed 10 Hz geophones. It eliminates the need for hand ‘planting’ of geophones, reducing time and costs. With the use of current survey techniques all data obtained with this instrument are being transferred in to 2D and 3D maps. This process is becoming more automatic.
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Paz, Maria, Francisco Alcalá, Ana Medeiros, Pedro Martínez-Pagán, Jaruselsky Pérez-Cuevas, and Luís Ribeiro. "Integrated MASW and ERT Imaging for Geological Definition of an Unconfined Alluvial Aquifer Sustaining a Coastal Groundwater-Dependent Ecosystem in Southwest Portugal." Applied Sciences 10, no. 17 (August 26, 2020): 5905. http://dx.doi.org/10.3390/app10175905.
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This paper integrates multichannel analysis of surface waves (MASW) and time-lapse electrical resistivity tomography (ERT) to define aquifer geometry and identify transient groundwater features of the Cascalheira Stream Basin Holocene alluvial aquifer (aquifer H), which contributes to the Santo André Lagoon, part of a coastal groundwater-dependent ecosystem (GDE), located in southwest Portugal. MASW measures shear-wave velocity (VS), allowing one to obtain steady geological models of the subsurface, and ERT measures subsurface electrical resistivity (ER), being subjected to ambient changes. MASW enables disambiguation of geological structures in low ER environments, such as coastal areas. This research covered one natural year and involved one MASW campaign, four ERT campaigns, and additional geological field surveys and groundwater monitoring to assist interpretation of results. In the area, the conjugate NW–SE and NE–SW strike-slip fault systems determine compartmentalization of geological structures and subsequent accommodation space for Holocene sedimentation. MASW and ERT surveys show how the NW–SE system deepens these structures toward the coast, whereas the NE–SW system generates small horsts and grabens, being one of these occupied by aquifer H. From upstream to downstream, aquifer H thickness and width increase from 10 m to 12 m and from 140 m to 240 m, respectively. Performance of VS and ER models was satisfactory, with a normalized error of the VR and ER models in the 0.01–0.09 range, meaning that a quantitative quota of uncertainty can be segregated from the overall uncertainty of groundwater models without substantially affecting its simulations accuracy. This methodology seeks to improve the design of shallow groundwater research in GDE preservation policies.
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López, Fernando, Manuel Navarro, Pedro Martínez-Pagán, Antonio García-Jerez, Jaruselsky Pérez-Cuevas, and Takahisa Enomoto. "Vs30 Structure of Almeria City (SE Spain) Using SPAC and MASW Methods and Proxy Correlations." Geosciences 12, no. 11 (October 31, 2022): 403. http://dx.doi.org/10.3390/geosciences12110403.
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The topographic slope method is an innovative, fast and very low-cost technique for estimating the average S-wave velocity in the upper 30 m (Vs30) based on the relationship between this quantity and the slope of the ground, obtained using a Digital Elevation Model (DEM). The method is based on the good linear correlations log(Vs30)–log(slope) found experimentally, which, ideally, should be determined for each region. If measured Vs30 data are not available to carry out this fitting for the study area, correlations from other areas could be used, although the reliability of the estimated Vs30 results would be lower. In this article, Vs30 observations are made for the city of Almeria, using Spatial Autocorrelation Surveys (SPAC) and Multichannel Analysis of Surface Waves (MASW), obtaining two types of fitting: (a) linear relationship log(Vs30)–log(slope); and (b) considering additional dependence on geological units. The reliability, evaluated by Multiple R-Squared (MRS), varies between 79.2% in the first case and 87.0% in the second, lowering the mean absolute values of the residuals at the observation points in the first case from 40.0 m/s to 29.0 m/s. Using a more generic correlation obtained for other areas of the world, the mean absolute residuals increase to 74.7 m/s.
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Guedes, Victor José Cavalcanti Bezerra, Welitom Rodrigues Borges, Luciano Soares da Cunha, and Susanne Taina Ramalho Maciel. "Spatial Autocorrelation of Passive Surface Wave Data for Assessment of an Earth Dam in Brasília, Brazil." Brazilian Journal of Geophysics 39, no. 4 (December 6, 2021): 551. http://dx.doi.org/10.22564/rbgf.v39i4.2115.
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ABSTRACT. Surface wave methods are commonly applied to engineering problems for S-wave velocity estimations. Conventional active Multichannel Analysis of Surface Waves (MASW) surveys for earth dam assessment suffer from limitations mainly associated to restrict depth of investigation and negative influences of near noise sources. In Brazil, the need to image around noisy sites over 30 m deep, which are non-ideal contexts for traditional active seismic data campaigns, is commonly in demand. We acquired ten minutes of ambient vibration data at the crest of a large earth dam in Brasília, Federal District. The Spatial Autocorrelation (SPAC) method was applied to develop a 2D S-wave model velocity using surface wave generated from passing vehicles on the adjacent road. A maximum depth of 42 m was achieved, and the model presented a S-wave velocity range from 274 m/s up to 713 m/s. The water level, foundation ground and possible low and high anomalous compaction zones were interpreted. Vs30 was found to vary from stiff to very dense soil along the profile, with higher values observed towards the left abutment.Keywords: earth dam; SPAC; MAM; S-wave; ambient noise. Autocorrelação Espacial de Dados Passivos de Ondas de Superfície para Avaliação de uma Barragem de Terra em Brasília, BrasilRESUMO. Métodos de onda de superfície são rotineiramente aplicados a problemas de engenharia para obtenção de estimativas de velocidade da onda S. A realização de levantamentos de Análise Multicanal de Ondas de Superfície (MASW) ativos convencionais para avaliação de barragens de terra sofrem limitações principalmente associadas à profundidade de investigação restrita e às influências negativas de fontes de ruído próximas. No Brasil, ocorre a necessidade de obter resultados em locais ruidosos com mais de 30 m de profundidade, que são contextos não ideais para as campanhas de sísmica ativa tradicionais. Dez minutos de dados de vibração ambiental foram registrados na crista de uma grande barragem de terra em Brasília, Distrito Federal. O método de Autocorrelação Espacial (SPAC) foi aplicado para desenvolver um modelo 2D da velocidade de onda S considerando ondas de superfície geradas a partir do tráfego de veículos na rodovia adjacente. Foi atingida uma profundidade máxima de 42 m e o modelo apresentou uma faixa de velocidade da onda S de 274 m/s a 713 m/s. Foram interpretados o nível freático, terreno de fundação e possíveis zonas anômalas de compactação baixa e mais elevada. Verificou-se que o Vs30 varia de solo rígido a muito denso ao longo do perfil, com valores mais altos observados em direção à ombreira esquerda.Palavras-chave: barragem de terra; SPAC; MAM; onda S; ruído ambiental.
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Dismuke, James N. "Nonlinear shear stress reduction factor (rd) for assessment of liquefaction potential in Christchurch Central Business District." Bulletin of the New Zealand Society for Earthquake Engineering 47, no. 1 (March 31, 2014): 1–14. http://dx.doi.org/10.5459/bnzsee.47.1.1-14.
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Simplified procedures for evaluating liquefaction triggering potential use the nonlinear shear stress reduction factor, rd, to estimate the peak earthquake-induced cyclic shear stress within the soil strata. Previous studies have derived rd by considering the response of representative ground profiles subjected to input ground motions with a range of ground motion characteristics. In this study, site–specific rd for serviceability limit state (SLS) and ultimate limit state (ULS) design ground motions are developed using site response models of the Christchurch Central Business District (CBD). The site response models are generated for typical geologic conditions of Christchurch CBD with shear wave velocity, Vs, profiles developed from the results of multichannel analysis of surface waves (MASW) surveys conducted across Christchurch CBD. A total of 528 simulations were conducted using 1D nonlinear time domain site response analyses using a suite of input ground motions that are representative of controlling ground motion scenarios for seismic hazard of Christchurch. The results of the ground response analyses are used to determine Christchurch CBD-specific rd relationships for liquefaction triggering assessments. The proposed relationships provide a better estimate of the cyclic stress ratios induced below Christchurch CBD when subjected to design SLS and ULS ground motions as compared to typical practice using generic liquefaction assessment methodologies.
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Morgan, David, David Gunn, Andres Payo, and Michael Raines. "Passive Seismic Surveys for Beach Thickness Evaluation at Different England (UK) Sites." Journal of Marine Science and Engineering 10, no. 5 (May 13, 2022): 667. http://dx.doi.org/10.3390/jmse10050667.
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In an era of environmental change leading to rising sea levels and increased storminess, there is a need to quantify the volume of beach sediment on the coast of Britain in order to assess the vulnerability to erosion using cheap, easy-to-deploy and non-invasive methods. Horizontal-to-vertical spectral ratio (HVSR) is a technique that uses the natural background seismic ‘noise’ in order to determine the depth of underlying geological interfaces that have contrasting physical properties. In this study, the HVSR technique was deployed at a number of settings on the coast of England that represented a range of different compositions, geomorphology, and underlying bedrock. We verified the results by comparison to other survey techniques, such as ground-penetrating RADAR, multichannel analysis of surface waves (MASW), and cone penetration tests. At locations where there was sufficient contrast in physical properties of the beach material compared to the underlying bedrock, the beach thickness (and therefore the volume of erodible material) was successfully determined, showing that HVSR is a useful tool to use in these settings.
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Darvasi, Yaniv, and Amotz Agnon. "Calibrating a new attenuation curve for the Dead Sea region using surface wave dispersion surveys in sites damaged by the 1927 Jericho earthquake." Solid Earth 10, no. 2 (March 7, 2019): 379–90. http://dx.doi.org/10.5194/se-10-379-2019.
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Abstract. Instrumental strong motion data are not common around the Dead Sea region. Therefore, calibrating a new attenuation equation is a considerable challenge. However, the Holy Land has a remarkable historical archive, attesting to numerous regional and local earthquakes. Combining the historical record with new seismic measurements will improve the regional equation. On 11 July 1927, a rupture, in the crust in proximity to the northern Dead Sea, generated a moderate 6.2 ML earthquake. Up to 500 people were killed, and extensive destruction was recorded, even as far as 150 km from the focus. We consider local near-surface properties, in particular, the shear-wave velocity, as an amplification factor. Where the shear-wave velocity is low, the seismic intensity far from the focus would likely be greater than expected from a standard attenuation curve. In this work, we used the multichannel analysis of surface waves (MASW) method to estimate seismic wave velocity at anomalous sites in Israel in order to calibrate a new attenuation equation for the Dead Sea region. Our new attenuation equation contains a term which quantifies only lithological effects, while factors such as building quality, foundation depth, topography, earthquake directivity, type of fault, etc. remain out of our scope. Nonetheless, about 60 % of the measured anomalous sites fit expectations; therefore, this new ground-motion prediction equation (GMPE) is statistically better than the old ones. From our local point of view, this is the first time that integration of the 1927 historical data and modern shear-wave velocity profile measurements improved the attenuation equation (sometimes referred to as the attenuation relation) for the Dead Sea region. In the wider context, regions of low-to-moderate seismicity should use macroseismic earthquake data, together with modern measurements, in order to better estimate the peak ground acceleration or the seismic intensities to be caused by future earthquakes. This integration will conceivably lead to a better mitigation of damage from future earthquakes and should improve maps of seismic hazard.
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Olafsdottir, Elin Asta, Sigurdur Erlingsson, and Bjarni Bessason. "Tool for analysis of multichannel analysis of surface waves (MASW) field data and evaluation of shear wave velocity profiles of soils." Canadian Geotechnical Journal 55, no. 2 (February 2018): 217–33. http://dx.doi.org/10.1139/cgj-2016-0302.
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Multichannel analysis of surface waves (MASW) is a fast, low-cost, and environmentally friendly technique to estimate shear wave velocity profiles of soil sites. This paper introduces a new open-source software, MASWaves, for processing and analysing multichannel surface wave records using the MASW method. The software consists of two main parts: a dispersion analysis tool (MASWaves Dispersion) and an inversion analysis tool (MASWaves Inversion). The performance of the dispersion analysis tool is validated by comparison with results obtained by the Geopsy software package. Verification of the inversion analysis tool is carried out by comparison with results obtained by the software WinSASW and theoretical dispersion curves presented in the literature. Results of MASW field tests conducted at three sites in south Iceland are presented to demonstrate the performance and robustness of the new software. The soils at the three test sites ranged from loose sand to cemented silty sand. In addition, at one site, the results of existing spectral analysis of surface waves (SASW) measurements were compared with the results obtained by MASWaves.
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Adegbola, R. B., K. F. Oyedele, L. Adeoti, and A. B. Adeloye. "Multichannel analysis of the surface waves of earth materials in some parts of Lagos State, Nigeria." Materials and Geoenvironment 63, no. 2 (September 1, 2016): 81–90. http://dx.doi.org/10.1515/rmzmag-2016-0007.
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Abstract We present a method that utilizes multichannel analysis of surface waves (MASW), which was used to measure shear wave velocities, with a view to establishing the probable causes of road failure, subsidence and weakening of structures in some local government areas in Lagos, Nigeria. MASW data were acquired using a 24-channel seismograph. The acquired data were processed and transformed into a two-dimensional (2-D) structure reflective of the depth and surface wave velocity distribution within a depth of 0–15 m beneath the surface using SURFSEIS software. The shear wave velocity data were compared with other geophysical/ borehole data that were acquired along the same profile. The comparison and correlation illustrate the accuracy and consistency of MASW-derived shear wave velocity profiles. Rigidity modulus and N-value were also generated. The study showed that the low velocity/ very low velocity data are reflective of organic clay/ peat materials and thus likely responsible for the failure, subsidence and weakening of structures within the study areas.
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Hasya, Cut Atika, Khaizal Khaizal, and Irwandi Irwandi. "Perbandingan Metode Multichannel Analysis of Surface Wave dan Metode Cone Penetration Test Terhadap Analisis Lapisan Tanah." Journal of The Civil Engineering Student 3, no. 1 (April 27, 2021): 14. http://dx.doi.org/10.24815/journalces.v3i1.12265.
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Analisis lapisan tanah yang dilakukan di lapangan salah satunya, metode Cone Penetration Test (CPT) yang menghasilkan parameter utama nilai tahanan ujung konus (qc). Sedangkan, metode Multichannel Analysis of Surface Wave (MASW) adalah metode dari bidang ilmu geofisika untuk menganalisis lapisan tanah yang dapat menghasilkan parameter kecepatan gelombang geser (Vs). Penelitian ini bertujuan untuk mendapatkan parameter gelombang geser (Vs) MASW dan parameter tahanan ujung CPT untuk menganalisis lapisan tanah serta membandingkan hasil dari kedua metode tersebut terhadap karakteristik lapisan tanah sebagai perencanaan pondasi bangunan sipil. Akuisisi data dilakukan di TPI (Tempat Pendaratan Ikan) Lampulo, Kecamatan Kuta Alam. Hasil penelitian pada pengukuran MASW didapatkan nilai Vs sebesar 70 - 130 m/s. Berdasarkan SNI 1726-2012, tanah pada lokasi penelitian termasuk ke dalam kategori Tanah Lunak (SE). Data CPT yang telah dikorelasikan meggunakan persamaan empiris menjadi nilai Vs menunjukkan hasil yang relatif sama dengan klasifikasi tanah pada MASW. Jenis pondasi yang sesuai diterapkan pada lokasi penelitian adalah pondasi tiang karena letak tanah keras berada pada kedalaman lebih dari 10 meter dibawah permukaan tanah.
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Long, Michael, and Shane Donohue. "In situ shear wave velocity from multichannel analysis of surface waves (MASW) tests at eight Norwegian research sites." Canadian Geotechnical Journal 44, no. 5 (May 1, 2007): 533–44. http://dx.doi.org/10.1139/t07-013.
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The multichannel analysis of surface waves (MASW) technique, which is used to determine shear wave velocity (Vs) and hence small strain stiffness (Gmax), has recently generated considerable interest in the geophysics community. This is because of the ease of carrying out the test and analysis of the data. The objective of this work was to assess the repeatability, accuracy, and reliability of MASW surface wave measurements for use in engineering studies. Tests were carried out at eight well-characterized Norwegian clay, silt, and sand research sites where Vs had already been assessed using independent means. As well as being easy and quick to use, the MASW technique gave consistent and repeatable results, and the MASW Vs profiles for the clay sites were similar to those obtained from other techniques. Reasonable results were also obtained for the silt and sand sites, with the best result being obtained for the finer silt. This work also confirms that MASW Vs clay profiles are comparable to those obtained by correlation with cone penetration test (CPT) data. For these sites there also seems to be a good correlation between normalized small strain shear modulus and in situ void ratio or water content, and the data fit well with published correlations for clays.Key words: soft clays, silts, sands, small strain stiffness, shear wave velocity.
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Gribler, Gabriel, Lee M. Liberty, and T. Dylan Mikesell. "High-Velocity Surface Layer Effects on Rayleigh Waves: Recommendations for Improved Shear-Wave Velocity Modeling." Bulletin of the Seismological Society of America 110, no. 1 (January 14, 2020): 279–87. http://dx.doi.org/10.1785/0120190120.
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ABSTRACT Soil stiffness estimates are critical to geologic hazard and risk assessment in urban centers. Multichannel analysis of surface-wave (MASW) data collection along city streets is now a standard, cost-effective, and noninvasive soil stiffness approximation tool. With this approach, shear-wave velocities (VS) are derived from Rayleigh-wave signals. Although the current MASW practice is to neglect the effect of a high-velocity road layer on soil VS estimates, our models show measurable impacts on Rayleigh-wave amplitudes and phase velocities when seismic data are acquired on a road surface. Here, we compare synthetic models with field MASW and downhole VS measurements. Our modeling indicates that a road layer attenuates Rayleigh-wave signals across all frequencies, introduces coherent higher-mode signals, and leads to overestimated VS and VS30 values. We show that VS30 can be overestimated by more than 7% when soft soils underlie a rigid road surface. Inaccurate VS estimates can lead to improper soil classification and bias earthquake site-response estimates. For road-based MASW data analysis, we recommend incorporating a surface road layer in the Rayleigh-wave inversion to improve VS estimate accuracy with depth.
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Chen, Hongbing, Bin Xu, Jiang Wang, Lele Luan, Tianmin Zhou, Xin Nie, and Yi-Lung Mo. "Interfacial Debonding Detection for Rectangular CFST Using the MASW Method and Its Physical Mechanism Analysis at the Meso-Level." Sensors 19, no. 12 (June 20, 2019): 2778. http://dx.doi.org/10.3390/s19122778.
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In this study, the transient multichannel analysis of surface waves (MASW) is proposed to detect the existence, the location and the length of interface debonding defects in rectangular concrete-filled steel tubes (CFST). Mesoscale numerical analysis is performed to validate the feasibility of MASW-based interfacial debonding detection. Research findings indicate that the coaxial characteristics in the Rayleigh wave disperse at the starting point of the debonding area and gradually restores at the end of the defect. For healthy specimens, the surface wave mode in CFST is closer to the Rayleigh wave. However, it can be treated as a Lamb wave since the steel plate is boundary-free on both sides in the debonding area. The displacement curves are further investigated with forward analysis to obtain the dispersion curves. The mesoscale numerical simulation results indicate that the propagation characteristic of the surface wave is dominated by the debonding defect. The detectability of interfacial debonding detection for rectangular CFST using the MASW approach is numerically verified in this study. The proposed MASW-based nondestructive testing technique can achieve bond-slip detection by comparing the variation trend of the coaxial characteristics in the time-history output signals and the dispersion curves obtained from the forward analysis, for avoiding misjudgment of the experimental observations.
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Olafsdottir, Elin Asta, Sigurdur Erlingsson, and Bjarni Bessason. "Open-Source MASW Inversion Tool Aimed at Shear Wave Velocity Profiling for Soil Site Explorations." Geosciences 10, no. 8 (August 17, 2020): 322. http://dx.doi.org/10.3390/geosciences10080322.
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The shear wave velocity profile is of primary interest for geological characterization of soil sites and elucidation of near-surface structures. Multichannel Analysis of Surface Waves (MASW) is a seismic exploration method for determination of near-surface shear wave velocity profiles by analyzing Rayleigh wave propagation over a wide range of wavelengths. The inverse problem faced during the application of MASW involves finding one or more layered soil models whose theoretical dispersion curves match the observed dispersion characteristics. A set of open-source MATLAB-based tools for acquiring and analyzing MASW field data, MASWaves, has been under development in recent years. In this paper, a new tool, using an efficient Monte Carlo search technique, is introduced to conduct the inversion analysis in order to provide the shear wave velocity profile. The performance and applicability of the inversion scheme is demonstrated with synthetic datasets and field data acquired at a well-characterized geotechnical research site.
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Neducza, Boriszláv. "Stacking of surface waves." GEOPHYSICS 72, no. 2 (March 2007): V51—V58. http://dx.doi.org/10.1190/1.2431635.
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The seismic surface wave method (SWM) is a powerful means of characterizing near-surface structures. Although the SWM consists of only three steps (data acquisition, determination of dispersion curves, and inversion), it is important to take considerable care with the second step, determination of the dispersion curves. This step is usually completed by spectral analysis of surface waves (SASW) or multichannel analysis of surface waves (MASW). However, neither method is ideal, as each has its advantages and disadvantages. SASW provides higher horizontal resolution, but it is very sensitive to coherent noise and individual geophone coupling. MASW is a robust method able to separate different wave types, but its horizontal resolution is lower. Stacking of surface waves (SSW) is a good compromise between SASW and MASW. Using a reduced number of traces increases the horizontal resolution of MASW, and utilizing other shot records with the same receivers compensates for the decreased signal-to-noise ratio. The stacking is realized by summing the [Formula: see text] amplitude spectra of windowed shot records, where windowing produces higher horizontal resolution and stacking produces improved data quality. Mixing is applied between the stacks derived with different parameters, as different frequency ranges require different windowing. SSW was tested and corroborated on a deep seismic data set. Horizontal resolution is validated by [Formula: see text] plots at different frequencies, and [Formula: see text] plots present data quality.
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Farhan, Muhammad, and Gunawan Handayani. "Shear Wave Velocity Analysis of 2-D Multichannel Analysis of Surface Wave (MASW) to investigate subsurface Fault of Alternative Bridge Construction in Kelok Sago Jambi." Jurnal Matematika dan Sains 25, no. 1 (September 2020): 18–20. http://dx.doi.org/10.5614/jms.2020.25.1.4.
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Every geotechnical measurement requires geophysical methods to classify soil types under the ground. S-wave velocity (Vs), P-wave velocity (Vp), and density (ρ), are the most important parameters in the classification of soils. There are various methods to determine Vs, one of them is P-S logging method. However, this method is less suitable to be applied in urban areas due to the difficulties of data acquisition and high expense in operational costs. In 1999, a seismic method uses surface waves to de-termine Vs profile with a higher signal to noise ratio which was known by the name of Multichannel Analysis of Surface Waves (MASW). A surface wave, especially Rayleigh wave, creeps slowly on the surface with a larger amplitude than a body wave. The wavelengths of the surface wave will disperse in the layers system i.e. the phase velocity of the surface waves is now func-tion of frequency. MASW 2-D method is used in this paper to determine subsoil properties and to identify the fault under the bridge abutments plan (abutment 1 and abutment 2) in Kelok Sago Jambi.
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Ivanov, Julian, Richard D. Miller, Pierre Lacombe, Carole D. Johnson, and John W. Lane. "Delineating a shallow fault zone and dipping bedrock strata using multichannal analysis of surface waves with a land streamer." GEOPHYSICS 71, no. 5 (September 2006): A39—A42. http://dx.doi.org/10.1190/1.2227521.
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The multichannel analysis of surface waves (MASW) seismic method was used to delineate a fault zone and gently dipping sedimentary bedrock at a site overlain by several meters of regolith. Seismic data were collected rapidly and inexpensively using a towed 30-channel land streamer and a rubberband-accelerated weight-drop seismic source. Data processed using the MASW method imaged the subsurface to a depth of about [Formula: see text] and allowed detection of the overburden, gross bedding features, and fault zone. The fault zone was characterized by a lower shear-wave velocity [Formula: see text] than the competent bedrock, consistent with a large-scale fault, secondary fractures, and in-situ weathering. The MASW 2D [Formula: see text] section was further interpreted to identify dipping beds consistent with local geologic mapping. Mapping of shallow-fault zones and dipping sedimentary rock substantially extends the applications of the MASW method.
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Tsuji, Takeshi, Tor Arne Johansen, Bent Ole Ruud, Tatsunori Ikeda, and Toshifumi Matsuoka. "Surface-wave analysis for identifying unfrozen zones in subglacial sediments." GEOPHYSICS 77, no. 3 (May 1, 2012): EN17—EN27. http://dx.doi.org/10.1190/geo2011-0222.1.
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To reveal the extent of freezing in subglacial sediments, we estimated S-wave velocity along a glacier using surface-wave analysis. Because the S-wave velocity varies significantly with the degree of freezing of the pore fluid in the sediments, this information is useful for identifying unfrozen zones within subglacial sediments, which again is important for glacier dynamics. We used active-source multichannel seismic data originally acquired for reflection analysis along a glacier at Spitsbergen in the Norwegian Arctic and proposed an effective approach of multichannel analysis of surface waves (MASW) in a glacier environment. Common-midpoint crosscorrelation gathers were used for the MASW to improve lateral resolution because the glacier bed has a rough topology. We used multimode analysis with a genetic algorithm inversion to estimate the S-wave velocity due to the potential existence of a low-velocity layer beneath the glacier ice and the observation of higher modes in the dispersion curves. In the inversion, we included information of ice thickness derived from high-resolution ground-penetrating radar data because a simulation study demonstrated that the ice thickness was necessary to estimate accurate S-wave velocity distribution of deep subglacial sediment. The estimated S-wave velocity distribution along the seismic line indicated that low velocities occurred below the glacier, especially beneath thick ice ([Formula: see text] for ice thicknesses larger than 50 m). Because this velocity was much lower than the velocity in pure ice ([Formula: see text]), the pore fluid was partially melted at the ice–sediment interface. At the shallower subglacial sediments (ice thickness less than 50 m), the S-wave velocity was similar to that of the pure ice, suggesting that shallow subglacial sediments are more frozen than sediments beneath thick ice.
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Coe, Joseph T., and Siavash Mahvelati. "Full Waveform Tomography to Address Challenges with Surface Wave Dispersion Information Caused by Significant Stochastic Variability of Subsurface Stiffness." Journal of Environmental and Engineering Geophysics 26, no. 4 (December 2021): 267–78. http://dx.doi.org/10.32389/jeeg21-013.
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Surface wave methods have increased in popularity as a means to acquire rapid and accurate shear wave velocity ( VS) profiles for engineering applications. Use of the multichannel analysis of surface waves (MASW) method, in particular, has proliferated due to multiple factors, including the ease with which strong signal-to-noise ratio can be achieved and the increased dispersion resolution offered by multichannel acquisitions. However, typical MASW processing to extract dispersion information assumes the surface waves propagate through a layered model. Errors can arise when significant lateral variability is present in the underlying stratigraphy as encountered in certain geologic settings such as residual deposits. This study investigated the effects of such variability on the dispersion information acquired with MASW. In particular, a spatially-correlated Gaussian random field was used to model the natural fluctuations in stiffness introduced by depositional processes, which differs from the approach in other studies where more specific anomalous features have been explored. Numerical modeling was subsequently performed to simulate surface wave propagation in the representative geotechnical site condition. The recovered surface waves were used to develop a subsurface stiffness profile using a dispersion-based pseudo-2D MASW approach and a tomographic approach using full waveform inversion (FWI). The results demonstrate that considerable natural spatial variability significantly complicates interpretation of dispersion information in two primary ways: (1) uncertainty can arise regarding what the dispersion curve exactly quantifies since none of the underlying VS profiles nor the average VS profile are obtained; and (2) the dispersion images exhibit evidence of false depth-related dispersion information indicative of multiple “fundamental” modes from the superposition of multiple stratigraphic units. The FWI procedure that bypasses extraction of dispersion information was found to better recover the underlying subsurface conditions when compared to the pseudo-2D MASW results at the cost of additional computational efforts.
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Guireli Netto, Leonides, Otavio Coaracy Brasil Gandolfo, Walter Malagutti Filho, and João Carlos Dourado. "NON-DESTRUCTIVE INVESTIGATION ON SMALL EARTH DAMS USING GEOPHYSICAL METHODS: SEISMIC SURFACE WAVE MULTICHANNEL ANALYSIS (MASW) AND S-WAVE REFRACTION SEISMIC METHODS." Brazilian Journal of Geophysics 38, no. 1 (March 4, 2020): 5. http://dx.doi.org/10.22564/rbgf.v38i1.2031.
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ABSTRACT. The application of non-destructive methods of investigation in dams, such as refractive seismic method and Multichannel Analysis of Surface Waves (MASW) are increasingly effective from the point of choosing the best dam site, as well as in the phases of construction and maintenance of the structure. The objective of the research was to apply geophysical methods in the structure of the dam to detect the internal flow of fluids, the presence of voids, find possible fracture zones and variations in the level of saturation of the massif, characteristics related to permeability and directly linked to the stability of the dam. In this way, geophysical methods have proved to be excellent tools, because, unlike instrumentation traditionally used in this type of monitoring, such as piezometers and water level indicators, they can cover a large study area quickly. This paper aims to present the results of the correlation between the MASW method and the S-wave seismic refraction method in two small earth dams in the countryside of the State of São Paulo, Brazil, more precisely in the cities of Cordeirópolis and Ipeúna. The main goal was to obtain the depths of the rocky top and the saturated/unsaturated zone of the earth dams using seismic tests under conditions of lack of information about the construction of the dam. The application of geophysical methods in dams that do not previously have important information (presence of drainage blanket, vertical/horizontal filters, for example) proves to be a very interesting non-destructive investigation technique.Keywords: geophysics in dams, MASW, seismic refraction, dam investigation. INVESTIGAÇÃO NÃO-DESTRUTIVA EM BARRAGENS DE TERRA DE PEQUENO PORTE USANDO MÉTODOS GEOFÍSICOS: ANÁLISE MULTICANAL DE ONDAS SUPERFICIAIS (MASW) E SÍSMICA DE REFRAÇÃO TOMOGRÁFICARESUMO. A aplicação de métodos não destrutivos de investigação em barragens, como o método da sísmica de refração e a análise multicanal de ondas de superfície (MASW), são cada vez mais eficazes desde a fase de escolha do melhor local para a instalação da barragem, bem como nas fases da construção e manutenção da estrutura. O objetivo da pesquisa foi aplicar métodos geofísicos na estrutura da barragem para detectar o fluxo interno de fluidos, a presença de vazios, encontrar possíveis zonas de fratura e variações no nível de saturação do maciço, características relacionadas à permeabilidade e diretamente ligadas à estabilidade da barragem. Desta forma, os métodos geofísicos se mostraram como excelentes ferramentas, pois puderam cobrir uma grande área de estudo com rapidez, diferentemente da tradicional instrumentação utilizada neste tipo de monitoramento, como piezômetros e indicadores do nível d'água. Este trabalho tem como objetivo apresentar os resultados da correlação entre o método MASW e o método sísmico de refração com ondas S em duas pequenas barragens de terra no interior do Estado de São Paulo, mais precisamente nas cidades de Cordeirópolis e Ipeúna. O objetivo principal foi o de obter as profundidades do topo rochoso e da zona saturada/insaturada das barragens de terra fazendo uso de ensaios sísmicos em condições de ausência de informações a respeito da construção do barramento. A aplicação de métodos geofísicos em barragens que não possuem previamente informações importantes (presença de tapete drenante, filtros verticais/horizontais, por exemplo) mostra-se como uma técnica de investigação não destrutiva bastante interessante.Palavras-chave: geofísica em barragens, MASW, sísmica de refração, investigação em barragens.
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Indanartha, Novien Ghoziana, Dwa Desa Warnana, and Amien Widodo. "Aplikasi Metode Multichannel Analysis Of Surface Wave (MASW) Sebagai Evaluasi Tapak Lokal Surabaya." Jurnal Geosaintek 4, no. 2 (August 31, 2018): 63. http://dx.doi.org/10.12962/j25023659.v4i2.4296.
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Tran, Khiem T., Justin Sperry, Michael McVay, Scott J. Wasman, and David Horhota. "Shear Wave Velocity Profiles of Roadway Substructures from Multichannel Analysis of Surface Waves and Waveform Tomography." Transportation Research Record: Journal of the Transportation Research Board 2655, no. 1 (January 2017): 36–44. http://dx.doi.org/10.3141/2655-06.
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Assessment of roadway subsidence caused by embedded low-velocity anomalies is critical to the health and safety of the traveling public. Surface-based seismic techniques are often used to assess roadways because of data acquisition convenience and large depths of characterization. To mitigate the negative impact of closing a traffic lane under traditional seismic testing, a new test system that uses a land streamer is presented. The main advantages of the system are the elimination of the need to couple the geophones to the roadway, the use of only one source at the end of the geophone array, and the movement of the whole test system along the roadway quickly. For demonstration, experimental data were collected on asphalt pavement overlying a backfilled sinkhole that was experiencing further subsidence. For the study, a 24-channel land streamer and a propelled energy generator to generate seismic energy were used. The test system was pulled by a pickup truck along the roadway and the data were collected with 81 shots at every 3 m for a road segment of 277.5 m, with a total data acquisition time of about 1 h. The measured seismic data set was analyzed by the standard multichannel analysis of surface waves (MASW) and advanced two-dimensional (2-D) waveform tomography methods. Eighty-one one-dimensional shear wave velocity (VS) profiles from the MASW were combined to obtain a single 2-D profile. The waveform tomography method was able to characterize subsurface structures at a high resolution (1.5- × 1.5-m cells) along the test length to a depth of 22.5 m. Very low S-wave velocity was obtained at the repaired sinkhole location. The 2-D VS profiles from the MASW and waveform tomography methods are consistent. Both methods were able to delineate high- and low-velocity soil layers and variable bedrock.
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Atan Obeten Egor. "Characterization of sub-surface structure, using seismic refraction and multi-channel analysis of surface waves methods in Ajere Ekori Yakurr LGA of cross river state." GSC Advanced Research and Reviews 16, no. 1 (July 30, 2023): 188–200. http://dx.doi.org/10.30574/gscarr.2023.16.1.0311.
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The study was to characterize the sub surface at Agere in Ekori, using seismic refraction method, multichannel analysis of surface waves technique and borehole intrusive technique. Data were collected using a 12channel seismograph and other accessories required for seismic refraction data collection. Software called seismicimager was used to examine the data. The primary wave velocity in the first layer varied from 690 m/s at 4.2 m to 96 m/s at 7.3 m. A Vp range of 315 m/s to 484 m/s at a depth of 2 m is present inside the layer and represents the organic soil constituents. A Vp range of 669 m/s to 1756 m/s represents loose sand (dry), loose made ground (rubble), landfill rubbish, disturbed soil, and clay landfill, all within a depth of 2.3 m to 12.1 m. In addition to the borehole intrusive method, multichannel analysis of surface wave (MASW) techniques was used to calculate the soil profile based on velocity. The source was a 7 kg sledge hammer, the detectors (receivers) were 24 units of 4.5 Hz geophones, and the recorder was a Terraloc Mark 8 ABEM. Seismicimager software was used for analysis. At Ajere 1 through 6, the MASW test configuration employed 5 m geophone spacing and a source offset distance of 5 m, while at Ajere 7, it used 1 m geophone spacing and a source offset distance of 2 m. Near the boreholes, all of the MASW test arrays were run. The trustworthy seismic data from Ajere 1 to 6 at depths of 0.7 m to 13.1 m and 4.7 m to 17 m. Based on SPT N values, the results showed that the shear wave velocities had been classified into three layers of soil: very soft, soft, and firm. The velocities below 164 m/s, between 164 and 190, and 190 m/s to 320 m/s were classified as these soil types. In the meantime, a drilling invasive technique based on SPT N value determines changes in the soil layer. Hard material shear wave velocity data was not provided. In conclusion, because of its non-destructive, non-invasive nature and relative speed of evaluation, the MASW technique has the potential to be adapted in soil study to complement intrusive technique.
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Lu, Zhiqu. "An acoustic near surface soil profiler using surface wave method." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A58. http://dx.doi.org/10.1121/10.0010649.
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An acoustic soil profiler, using a so-called the high-frequency multi-channel analysis of surface waves (HF-MASW) method, has been developed, which uses surface (Rayleigh) waves to measure soil profile in terms of the shear (S) wave velocity as a function of depth, up to a 2.5 m deep below the surface. Several practical techniques have been developed to enhance the HF-MASW method, including (1) a variable sensor spacing configuration, (2) the self-adaptive method, and (3) the phase-only signal processing. Fundamentally, the S-wave velocity is related to soil mechanical and hydrological properties through the principle of effective stress. Therefore, the measured two-dimensional S-wave velocity images reflect the temporal and spatial variations of soils due to weather effects, geological anomalies, and anthropologic activities. Several HF-MASW applications will be reported, including (1) near surface soil profiling, (2) a long-term-survey for studying weather and seasonal effects, (3) short-term monitoring rain fall events, (4) detecting fraigpan layers, and (5) a farmland compaction study. This acoustic soil profiler can be used for agricultural, environmental, civil engineering, and military applications.
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Yadav, Shubhamjeet, Madan Chandra Maurya, and Keshav Kumar Sharma. "Seismic Site Response Analysis of MMMUT Gorakhpur of Uttar Pradesh, India." IOP Conference Series: Materials Science and Engineering 1273, no. 1 (January 1, 2023): 012005. http://dx.doi.org/10.1088/1757-899x/1273/1/012005.
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Abstract An endeavour has been made to assess the spatial fluctuation of the profundity of endured and designing bedrock in Gorakhpur Uttar Pradesh, North India utilizing Multichannel Analysis of Surface Wave (MASW) study. One-layered MASW study has been done at Madan Mohan Malaviya University of Technology, Gorakhpur campus and Shear-wave Velocity V S 30 are estimated. MASW overview at 3 location and a Standard Penetration Test SPT-N from the profound geotechnical boreholes data used for comparison of site classification. The deduction of this work might be utilized as contributions for seismic tremor risk the board by lessening the seriousness of earthquake shaking through plan of tremor Earthquake risk resilient structure strong designs. The data that collected from the MASW experimental setup is feed using the software ParkSEIS (v.3.0), we obtain Shear Wave Velocity (VS30 ). The obtained V S 30 is used to plot Response Spectra for MMMUT Gorakhpur. The Time History data used in this thesis is Nepal Earthquake 2015 data which is collected from Indian Metrological Department (IMD) Delhi, India. SPT-N value data is collected from Awas Vikas Parishad for the New Administration Building build at MMMUT campus Gorakhpur. The Time History data of Nepal Earthquake 2015 is analysed using DEEPSOIL v7 Software and a systematic layer wise study of MMMUT Campus soil is carried out, results such as Ground Motion Parameters, Response Spectra, Spectral acceleration vs Frequency plot, Tripartite Spectrum and Response spectra corresponding to 5% damping are obtained.
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Tokeshi, K., P. Harutoonian, C. J. Leo, and S. Liyanapathirana. "Use of surface waves for geotechnical engineering applications in Western Sydney." Advances in Geosciences 35 (June 27, 2013): 37–44. http://dx.doi.org/10.5194/adgeo-35-37-2013.
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Abstract. Current in situ methods used to geotechnically characterize the ground are predominantly based on invasive mechanical techniques (e.g. CPT, SPT, DMT). These techniques are localized to the tested area thus making it quite time consuming and costly to extensively cover large areas. Hence, a study has been initiated to investigate the use of the non-invasive Multichannel Analysis of Surface Waves (MASW) and Multichannel Simulation with One Receiver (MSOR) techniques to provide both an evaluation of compacted ground and a general geotechnical site characterization. The MASW technique relies on the measurement of active ambient vibrations generated by sledgehammer hits to the ground. Generated vibrations are gathered by interconnected electromagnetic geophones set up in the vertical direction and in a linear array at the ground surface with a constant spacing. The MSOR technique relies on one sensor, one single geophone used as the trigger, and multiple impacts are delivered on a steel plate at several distances in a linear array. The main attributes of these non-invasive techniques are the cost effectiveness and time efficiency when compared to current in situ mechanical invasive methods. They were applied to infer the stiffness of the ground layers by inversion of the phase velocity dispersion curves to derive the shear wave velocity (Vs) profile. The results produced by the MASW and the MSOR techniques were verified against independent mechanical Cone Penetration Test (CPT) and Standard Penetration Test (SPT) data. This paper identifies that the MASW and the MSOR techniques could be potentially useful and powerful tools in the evaluation of the ground compaction and general geotechnical site characterization.
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El-Raouf, Amr Abd, Ibrar Iqbal, Julia Meister, Kamal Abdelrahman, Hassan Alzahrani, and Osman M. Badran. "Earthflow reactivation assessment by multichannel analysis of surface waves and electrical resistivity tomography: A case study." Open Geosciences 13, no. 1 (January 1, 2021): 1328–44. http://dx.doi.org/10.1515/geo-2020-0310.
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Abstract In this study, we investigated the stability and reactivation of preexisting Tonghua landslide deposits in China, including the adjacent stable slope. We used an integrated approach, combining a multichannel analysis of surface waves (MASW) and electrical resistivity tomography (ERT). We used ERT to determine groundwater seepage paths, weathering conditions, water content, and the depth to bedrock. High-resolution two-dimensional (2D) shear-wave velocity MASW images, on the other hand, played an essential role in detecting both horizontal and vertical compositions, disjointedness, and sliding surfaces related to lithological borders. Based on seismic models, we considered four geological layers encountered in the stable slope, including fractured (gravel) and weathered (phyllite) materials, as a sliding mass. We combined the 2D resistivity profiles obtained to create pseudo-three-dimensional ERT images to estimate water-saturated and unsaturated masses. From the tomography results, we identified different preexisting deposits, including buried arable clay deposits, old accumulated earthflow deposits, a water accumulation zone, and a fissure runoff. Based on the resistivity results, the bottom of the earthflow deposits is susceptible to water, and oversaturation can reactivate the earthflow.
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Kumar, Jyant, and Tarun Naskar. "Resolving phase wrapping by using sliding transform for generation of dispersion curves." GEOPHYSICS 82, no. 3 (May 1, 2017): V127—V136. http://dx.doi.org/10.1190/geo2016-0207.1.
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The complexity involved with the phase unwrapping procedure, while performing the existing spectral analysis of surface waves (SASW) on the basis of two sensors, makes it difficult to automate and requires frequent manual judgment. As a result, this approach generally becomes tedious and may yield erroneous results. The multichannel analysis of surface waves (MASW) technique can resolve the problem of phase wrapping. However, the MASW technique normally requires a large number of closely spaced sensors, typically 24–48 or even more. We have developed a new method that is fast, accurate, and generally resolves the unwrapping of phase with the use of just two sensors, provided the signal-to-noise ratio remains high. In this approach, the unwrapping of the phase can be performed without any manual intervention and an automation of the process becomes feasible. A few examples, involving synthetic test data and surface-wave tests, have been tested to determine the efficacy of our approach. Comparisons of the results have been made with the corresponding solutions using existing SASW and MASW techniques.
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Cheng, Feng, Jianghai Xia, Yinhe Luo, Zongbo Xu, Limin Wang, Chao Shen, Ruofei Liu, Yudi Pan, Binbin Mi, and Yue Hu. "Multichannel analysis of passive surface waves based on crosscorrelations." GEOPHYSICS 81, no. 5 (September 2016): EN57—EN66. http://dx.doi.org/10.1190/geo2015-0505.1.
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Passive seismic methods in highly populated urban areas have gained much attention from geophysics and civil engineering communities because traditional seismic surveys, especially in complex urbanized environments, might be improperly applied. In passive seismic methods, directional noise sources will inevitably bring azimuthal effects and spatial aliasing to dispersion measurements due to the fact that true randomness of ambient noise cannot be achieved in reality. To solve these problems, multichannel analysis of passive surface (MAPS) waves based on long noise sequence crosscorrelations is proposed. We have introduced a hybrid method of seismic interferometry and the roadside passive multichannel analysis of surface waves (MASW) using crosscorrelation to produce common virtual source gathers from 1 h multichannel noise records. Common virtual source gathers are then used to do dispersion analysis with an active scheme based on phase-shift measurement. Synthetic tests demonstrated the advantages of this method with azimuthal adjustment and dispersion imaging for directional noise source distribution. Two field applications were conducted, and results from the roadside passive MASW, MAPS, and spatial autocorrelation method were compared. Our study indicated the superiority of MAPS over the roadside passive MASW on the validity of azimuth detection, feasibility of combining the active MASW and MAPS, and accuracy in determining dispersion energy trends, especially at a relative low-frequency range ([Formula: see text]) in urban areas.
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Jafri, Nur Jihan Syamimi, Mohd Asri Ab Rahim, Mohd Zulham Affandi Mohd Zahid, Nor Faizah Bawadi, Muhammad Munsif Ahmad, Ahmad Faizal Mansor, and Wan Mohd Sabki Wan Omar. "Assessment of soil compaction properties based on surface wave techniques." E3S Web of Conferences 34 (2018): 01002. http://dx.doi.org/10.1051/e3sconf/20183401002.
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Soil compaction plays an important role in every construction activities to reduce risks of any damage. Traditionally, methods of assessing compaction include field tests and invasive penetration tests for compacted areas have great limitations, which caused time-consuming in evaluating large areas. Thus, this study proposed the possibility of using non-invasive surface wave method like Multi-channel Analysis of Surface Wave (MASW) as a useful tool for assessing soil compaction. The aim of this study was to determine the shear wave velocity profiles and field density of compacted soils under varying compaction efforts by using MASW method. Pre and post compaction of MASW survey were conducted at Pauh Campus, UniMAP after applying rolling compaction with variation of passes (2, 6 and 10). Each seismic data was recorded by GEODE seismograph. Sand replacement test was conducted for each survey line to obtain the field density data. All seismic data were processed using SeisImager/SW software. The results show the shear wave velocity profiles increase with the number of passes from 0 to 6 passes, but decrease after 10 passes. This method could attract the interest of geotechnical community, as it can be an alternative tool to the standard test for assessing of soil compaction in the field operation.
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Jusoh, Hisyam, Syed Baharom Syed Osman, and Khairul Arifin Mohd Noh. "Usability of the surface wave method in assessment for subsurface investigation." IOP Conference Series: Earth and Environmental Science 1003, no. 1 (April 1, 2022): 012039. http://dx.doi.org/10.1088/1755-1315/1003/1/012039.
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Abstract Soil borehole drilling incorporating Standard Penetration Test (SPT) is frequently used for subsurface profiling and geotechnical calculations such as soil bearing capacity. Despite this conventional application, there are several limitations of soil boring and SPT involves. The primary objective is to propose an alternative method for geotechnical engineering application of soil profiling as supporting data by conducting Multichannel Analysis Surface Wave (MASW) for site investigation. In this study, the MASW was utilized to verify the reliability and capability of this method on conversion of shear wave velocity, Vs to SPT-N value. The calculated SPT-N value based on Vs using selected equation (Vs = 97N0.314) showed the reliability of the correlation between actual SPT-N value relationship was found strong (R2 = 0.8343). Results from the case study in general reveal the shear wave velocity (Vs) profile shows reading of 80 m/s to 160 m/s for the first 2-3 meter depth representing soft soil overlaying 2 meter layer of stiff soil with Vs between 130 m/s to 170 m/s followed by 4-10 meter hard material having Vs value between 190 m/s to 280 m/s before reaching harder stratum of 350 m/s and more. Therefore, the MASW can possibly be applied for SPT-N value determination as supporting data to the conventional SPT machine. The data of shear wave velocity also were correlated with actual SPT-N value so that the produced equation and can be applied based on the local region. Hence, produced empirical formulas from this study intend to provide the geotechnical engineer with a quick preliminary method of site investigation/assessment.
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Dong, Yang, Shengchun Piao, Lijia Gong, Guangxue Zheng, Kashif Iqbal, Shizhao Zhang, and Xiaohan Wang. "Scholte Wave Dispersion Modeling and Subsequent Application in Seabed Shear-Wave Velocity Profile Inversion." Journal of Marine Science and Engineering 9, no. 8 (August 2, 2021): 840. http://dx.doi.org/10.3390/jmse9080840.
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Recent studies have illustrated that the Multichannel Analysis of Surface Waves (MASW) method is an effective geoacoustic parameter inversion tool. This particular tool employs the dispersion property of broadband Scholte-type surface wave signals, which propagate along the interface between the sea water and seafloor. It is of critical importance to establish the theoretical Scholte wave dispersion curve computation model. In this typical study, the stiffness matrix method is introduced to compute the phase speed of the Scholte wave in a layered ocean environment with an elastic bottom. By computing the phase velocity in environments with a typical complexly varying seabed, it is observed that the coupling phenomenon occurs among Scholte waves corresponding to the fundamental mode and the first higher-order mode for the model with a low shear-velocity layer. Afterwards, few differences are highlighted, which should be taken into consideration while applying the MASW method in the seabed. Finally, based on the ingeniously developed nonlinear Bayesian inversion theory, the seafloor shear wave velocity profile in the southern Yellow Sea of China is inverted by employing multi-order Scholte wave dispersion curves. These inversion results illustrate that the shear wave speed is below 700 m/s in the upper layers of bottom sediments. Due to the alternation of argillaceous layers and sandy layers in the experimental area, there are several low-shear-wave-velocity layers in the inversion profile.
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Ashraf, M. A. M., N. S. Kumar, R. Yusoh, Z. A. M. Hazreek, and M. Aziman. "Site Classification using Multichannel Channel Analysis of Surface Wave (MASW) method on Soft and Hard Ground." Journal of Physics: Conference Series 995 (April 2018): 012108. http://dx.doi.org/10.1088/1742-6596/995/1/012108.
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Ikeda, Tatsunori, and Takeshi Tsuji. "Two-station continuous wavelet transform cross-coherence analysis for surface-wave tomography using active-source seismic data." GEOPHYSICS 85, no. 1 (January 1, 2020): EN17—EN28. http://dx.doi.org/10.1190/geo2019-0054.1.
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ABSTRACT Surface-wave tomography has great potential to improve the lateral resolution of near-surface characterization compared to 2D surface-wave analysis with multichannel analysis of surface waves (MASW). Surface-wave tomography has been widely applied to obtain high-resolution maps of phase or group velocity from dispersion curves between pairs of stations in seismological studies. However, very few studies have done surface-wave tomography with active-source (exploration) seismic data, probably because extracting surface-wave dispersion curves between two stations is difficult due to the complex wave propagation in heterogeneous near-surface structures. Here, we describe a method to estimate reliable phase-velocity dispersion curves between two stations from exploration seismic data. In our approach, we compute cross coherences between pairs of stations to extract phase information, stacking the cross coherences from different shot gathers to improve the signal-to-noise ratio. To further distinguish surface-wave signals from noise in the time domain, we perform a time-frequency analysis using the continuous wavelet transform (CWT) on the stacked cross coherences. We used modeling of the wavelet transform between station pairs to extract phase-velocity dispersion curves from the stacked cross coherences. We apply this two-station CWT cross-coherence method to synthetic and field data sets. Both applications demonstrate that our method can extract stable phase-velocity dispersion curves between two stations better than two-station or multistation analysis without time-domain filtering. In phase-velocity distributions constructed by surface-wave tomography from the dispersion curves between two stations, the horizontal resolution is improved over MASW-based analyses. Improvement of the horizontal resolution is also achieved in S-wave velocity structures derived by inversion of the phase-velocity distributions. Our method is effective in estimating reliable phase-velocity dispersion curves and may contribute to constructing high-resolution S-wave velocity models located with a laterally heterogeneous structure, by subsequent surface-wave tomography and S-wave velocity inversion.
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Gribler, Gabriel, Lee M. Liberty, T. Dylan Mikesell, and Paul Michaels. "Isolating retrograde and prograde Rayleigh-wave modes using a polarity mute." GEOPHYSICS 81, no. 5 (September 2016): V379—V385. http://dx.doi.org/10.1190/geo2015-0683.1.
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Estimates of S-wave velocity with depth from Rayleigh-wave dispersion data are limited by the accuracy of fundamental and/or higher mode signal identification. In many scenarios, the fundamental mode propagates in retrograde motion, whereas higher modes propagate in prograde motion. This difference in particle motion (or polarity) can be used by joint analysis of vertical and horizontal inline recordings. We have developed a novel method that isolates modes by separating prograde and retrograde motions; we call this a polarity mute. Applying this polarity mute prior to traditional multichannel analysis of surface wave (MASW) analysis improves phase velocity estimation for fundamental and higher mode dispersion. This approach, in turn, should lead to improvement of S-wave velocity estimates with depth. With two simple models and a field example, we have highlighted the complexity of the Rayleigh-wave particle motions and determined improved MASW dispersion images using the polarity mute. Our results show that we can separate prograde and retrograde signals to independently process fundamental and higher mode signals, in turn allowing us to identify lower frequency dispersion when compared with single component data. These examples demonstrate that the polarity mute approach can improve estimates of S-wave velocities with depth.