Multichannel Analysis Of Surface Waves Research Articles

Field testing of municipal solid waste and estimation of waste properties

As biodegradation proceeds, municipal solid wastes (MSW) acquire pronounced soil-like properties and upon completion of the process can be used as the foundation. The solid waste massif is an inhomogeneous soil-like mass which requires non-destructive and minimally invasive methods of research. The cone penetration testing of MSW by piezocone (CPTU) in combination with the multichannel analysis of surface waves (MASW) provide extensive data about physico-mechanical properties of wastes, which are usually unavailable in traditional approaches and which can be directly used in geotechnical stability calculations of the waste massif.

STUDY OF UNCERTAINTY OF THE INVERSION OF DISPERSION CURVES OF SURFACE WAVES USING ARTIFICIAL NEURAL NETWORKS

The results of using an adapted sampling algorithm by the Monte Carlo method to estimate the ambiguity domain of the inversion of synthetic dispersion curves of the phase velocities of surface waves using artificial neural networks are discussed in the paper. The expediency of using the considered algorithm for calculating a probabilistic estimate of the results of the inverse problem solution in the method of multichannel analysis of surface waves has been confirmed.

Integrated geophysical imaging of a mountain landslide – A case study from the Outer Carpathians, Poland

In the presented case study, the authors applied the multimethod approach utilising geophysical imaging with estimated uncertainty to the landslide in Cisiec, southwest Poland. Application of multiple geophysical methods such as electrical resistivity tomography (ERT), multichannel analysis of surface waves (MASW), refraction seismic method, ray-based seismic tomography, and reflection imaging was aimed at obtaining a detailed and high-resolution image of the subsurface. Drone-based digital terrain models (DTM) supported the subsurface imaging by providing a detailed view of the landslide surface. Accurate GPS-based geodesy conducted during data gathering was used to complete information about the topography of the area and correlate the results of geophysical surveys. The combination and transfer of information between methods allow solving multiple reflection imaging problems, especially lack of borehole information. The final result presents the detailed geophysical images of the landslide with a recognized depth of main slip surface ranging from 16 to 36 m. Because the study site is used as a ski slope, detailed information about the landslide structure is needed to provide safety for nearby construction. The methodology proposed in this paper can be used in similar case studies, where fast and cost-effective recognition of a landslide is required.

Evaluation of Physical and Geomechanical characteristics at a Steel Rolling Factory at Ataqa industrial zone, Suez, Egypt using Seismic Methods

Our investigations are aimed to calculate the physical and geomechanical characteristics needed to assess the geotechnical suitability of the subsurface at Ataqa industrial zone, Suez, Egypt for constructing some industerial facilities. To accomplish our target, four seismic profiles are conducted using the refraction technique to estimate the primary seismic wave velocity as well as four profiles using the method of Multichannel Analysis of Surface Waves for estimating the velocity of shear waves. The stage of processing and interpretation are performed through using the SeisImager/2D Software. The results clarify the existence of two layers to a depth of 18 m. The top layer ranges in thickness between 2 and 4m and has a primary wave velocity ranging between 924 and 1247 m/s and a shear wave velocity ranging between 530 and 745 m/s. On the other hand, the second layer possesses an average primary velocity ranging between 1277 and 1573 m/s and a shear wave velocity ranging between 684 and 853 m/s. The measured velocities are utilized to calculate many physical and geomechanical properties of the earth materials comprising the two layers in our study area. The integration between all these parameters proves the suitability of both layers for erecting the proposed constructions.

Geophysical techniques for characterisation of municipal solid waste landfills

This paper presents the seismic site characterisation of Mavallipura landfill in Bengaluru, India using multichannel analysis of surface waves (MASW). The survey was performed at top level up to a height of 25 m. Up to 6 m it consisted of uncompacted waste. Also, the shear-wave velocity increased with depth from approximately 74 to 150 m/s. A series of one- and two-dimensional MASW surveys at various levels of the landfill was carried out to map the site fully. A new empirical correlation between standard penetration test corrected N values and shear-wave velocity was also developed. The MASW survey results and correlation with the conventional geotechnical investigation are presented in this paper. The results showed that the seismic waves can achieve changes in shear-wave velocity and Poisson's ratio to conclude the amount of degradation taking place at the landfill and thereby provide some knowledge with regards to the properties required for evaluating seismic stability.

Evaluating the Earth Subsurface for Civil Engineering Site Characterization in Agege, Southwest Nigeria Using Integrated Geoelectrical and Multichannel Analysis of Surface Wave (MASW)

A geophysical investigation involving 1D Vertical Electrical Sounding (VES), 2D Electrical Resistivity Imaging (2D ERI) and Multichannel Analysis of Surface Wave (MASW) has been carried out at Agege, Lagos, Nigeria with a view to delineating the subsurface stratigraphy and locate some competent strata/stratum for founding civil engineering structures. Six (6) 200 m long traverses were established within the study area. Along these traverses, 2D ERI were carried out adopting Wenner electrode configuration. Vertical Electrical Sounding (VES) adopting Schlumberger electrode array were carried out at selected points along profiles 1, 2 and 3 to determine the lithological sequence at depth. MASW data also were acquired along traverses 1, 2 and 3. The data were processed and the result yielded interpretable 2D resistivity structure and geoelectrical parameters (layer resistivity, thicknesses and depth) from the VES. The interpreted VES results were used to generate geoelectric section while the MASW resulted in 2D velocity sections. Three subsoils including topsoil, clay and clayey sand/sand were delineated beneath the study area. The resistivity and thickness range of the layers are; topsoil (34.0-54.6 ohm-m, 0.9 – 1.7 m), clay (10.3 – 17.7 ohm-m, 8.9 – 12.3 m) and clayey sand/sand (48.9 – 323 ohm-m) while the S-wave velocity range for the subsoil falls between 40 – 500 m/sec.

Distributed acoustic sensing for shallow seismic investigations and void detection

During the past few decades, fiber-optic-based distributed acoustic sensing (DAS) has emerged as an affordable, easy-to-deploy, reliable, and noninvasive technique for high-resolution seismic sensing. We have determined that fiber deployments dedicated to near-surface seismic applications, commonly used for the detection and localization of voids, can be used effectively with conventional processing techniques. We tested a variety of small sources in different geologic environments. These sources, operated on and below the surface, were recorded by horizontal and vertical DAS arrays. Our results and comparisons to data acquired by vertical-component geophones demonstrate that DAS may be sufficient for acquiring near-surface seismic data. Furthermore, we tried to address the issue of directional sensing by DAS arrays and use it to solve the problem of wave-mode separation. Records acquired by a unique acquisition setup suggest that one can use the nature of standard DAS systems as uniaxial strainmeters to record separated wave modes. Finally, we applied two seismic methods on DAS data acquired at a test site: multichannel analysis of surface waves (MASW) and shallow diffraction imaging. These methods allowed us to determine the feasibility of using DAS systems for imaging shallow subsurface voids. MASW was used to uncover anomalies in the S-wave velocity, whereas shallow diffraction imaging was applied to identify the location of the void. The results we obtained illustrate that by using these methods we are able to accurately detect the true location of the void.

Multichannel analysis of surface waves based on short array stacked Correlation gather

Multichannel analysis of surface waves (MASW) has played an important role in shear wave velocity survey of subsurface. Modern urban engineering construction needs more and more high-resolution detection of shallow underground objects. However, the traditional MASW method will reduce the detection depth when the receiving array length is reduced to improve lateral resolution. We propose a modified multichannel analysis method of surface waves based on short array stacked correlation gather (SCG-MASW) to solve this problem. The geometry of SCG-MASW is same as MASW, but surface wave dispersion is derived from short array stacked correlation gather instead of shot gather. Both theoretical and experimental data show that the SCG-MASW can improve the lateral resolution by using short receiving array, while not reducing the detection depth.

Combining of MASW and GPR Imaging and Hydrogeological Surveys for the Groundwater Resource Evaluation in a Coastal Urban Area in Southern Spain

This paper conceptualizes and evaluates the groundwater resource in a coastal urban area hydrologically influenced by peri-urban irrigation agriculture. Adra town in southern Spain was the case study chosen to evaluate the groundwater resource contributed from the northern steep urban sector (NSUS) to the southern flat urban sector (SFUS), which belongs to the Adra River Delta Groundwater Body (ARDGB). The methodology included (1) geological and hydrogeological data compilation; (2) thirteen Multichannel Analysis of Surface Waves (MASW), and eight Ground Penetrating Radar (GPR) profiles to define shallow geological structures and some hydrogeological features; (3) hydrogeological surveys for aquifer hydraulic definition; (4) conceptualization of the hydrogeological functioning; and (5) the NSUS groundwater resource evaluation. All findings were integrated to prepare a 1:5000 scale hydrogeological map and cross-sections. Ten hydrogeological formations were defined, four of them (Paleozoic weathered bedrock, Pleistocene littoral facies, Holocene colluvial, and anthropogenic filling) in the NSUS contributing to the SFUS. The NSUS groundwater discharge and recharge are, respectively, around 0.28 Mm3 year−1 and 0.31 Mm3 year−1, and the actual groundwater storage is around 0.47 Mm3. The groundwater renewability is high enough to guarantee a durable small exploitation for specific current and future urban water uses which can alleviate the pressure on the ARDGB.

Data acquisition method and the effectiveness of multichannel analysis of surface waves for defect detections on small earthen dams

For small earthen dams, the stability and performance depend heavily on the leakage caused by various reasons, such as aging and lack of maintenance. The effective assessments of these dams are crucial prior to the possible engineering interventions. To this end, a field investigation was conducted to explore the effectiveness of multichannel analysis of surface wave (MASW) method in the detection of leakage zones in small earthen dams. A new method based on the updating strategy of subarrays was designed and used to acquire the surface wave data. The acquisition efficiency and dispersion features of the collected data were analyzed in details. The S-wave velocity inversion imaging of the target dam was also discussed. The results show that the newly designed method allows us to acquire data in a high efficiency. The method is expected to consume 48% shorter time than the commonly used one. The analysis reveals that the dispersion energy and dispersion curves of acquired surface waves are influenced by the subarray lengths. The effect is reflected in the distribution of the fundamental mode and dispersion curve in a limited way. In addition, the investigation results show that the leakage zones inside the dam can be characterized by the anomalous low-velocity area of the inverted pseudo-two-dimensional (2D) S-wave velocity profile, validating the applicability of MASW in detecting the leakage zones of small earthen dams.

Low-frequency ambient distributed acoustic sensing (DAS): case study from Perth, Australia

SUMMARYAmbient wavefield data acquired on existing (so-called ‘dark fibre’) optical fibre networks using distributed acoustic sensing (DAS) interrogators allow users to conduct a wide range of subsurface imaging and inversion experiments. In particular, recorded low-frequency (<2 Hz) surface-wave information holds the promise of providing constraints on the shear-wave velocity (VS) to depths exceeding 0.5 km. However, surface-wave analysis can be made challenging by a number of acquisition factors that affect the amplitudes of measured DAS waveforms. To illustrate these sensitivity challenges, we present a low-frequency ambient wavefield investigation using a DAS data set acquired on a crooked-line optical fibre array deployed in suburban Perth, Western Australia. We record storm-induced microseism energy generated at the nearby Indian Ocean shelf break and/or coastline in a low-frequency band (0.04−1.80 Hz) and generate high-quality virtual shot gathers (VSGs) through cross-correlation and cross-coherence interferometric analyses. The resulting VSG volumes clearly exhibit surface wave energy, though with significant along-line amplitude variations that are due to the combined effects of ambient source directivity, crooked-line acquisition geometry and the applied gauge length, fibre coupling, among other factors. We transform the observed VSGs into dispersion images using two different methods: phase shift and high-resolution linear Radon transform. These dispersion images are then used to estimate 1-D near-surface VS models using multichannel analysis of surface waves (MASW), which involves picking and inverting the estimated Rayleigh-wave dispersion curves using the particle-swarm optimization global optimization algorithm. The MASW inversion results, combined with nearby deep borehole information and 2-D elastic finite-difference modeling, show that low-frequency ambient DAS data constrain the VS model, including a low-velocity channel, to at least 0.5 km depth. Thus, this case study illustrates the potential of using DAS technology as a tool for undertaking large-scale surface wave analysis in urban geophysical and geotechnical investigations to depths exceeding 0.5 km.

Shear-wave velocity measurements and their uncertainties at six industrial sites

This study assesses the variability of shear-wave ( VS) profile determinations for a suite of methods at six industrial sites. The methods include active, consisting of multi-channel analysis of surface waves (MASW), as well as passive, consisting of refraction microtremor (ReMi), and extended spatial autocorrelation (ESAC). The purpose is to ascertain the effect of the higher level of ambient noise on the results from the different methods, as only a few of these many methods are commonly used for site characterization. The measured dispersion curves are in fair agreement with one another. The average coefficient of variation (CoV; the percentage ratio of the standard deviation to the mean) for the dispersion curves varied from 2.5% to 12.6%. In contrast, over the VS-depth domain, the average shear-wave velocity profiles to a depth z ( VS,Z) vary from 11.6% to 16.5% between the various methods at the different sites. This indicates that the variance among the individual methods can lead to significant misinterpretation of the shallow subsurface, while the average VS,Z is much more robust. This reaffirms its use (mainly as VS,30) in building codes and within ground motion prediction equations (GMPEs). At all six sites, because of inversion processes, the variability within each method ranges from 4% up to 14%. There is no correlation between the test type and the CoV. Our study focused on surface-wave measurements in noisy industrial environments, where the signals processed are typically complex. Despite this complexity, our results suggest that such tests are also applicable to industrial zones, where the noisy environment constitutes an energy source.

Evaluation of geophysical methods for characterizing industrial and municipal waste dumps

The main aim of this study was to assess the suitability of geophysical methods for investigating old waste dumps. Electrical Resistivity Tomography (ERT), Seismic Refraction Tomography (SRT), Multichannel Analysis of Surface Waves (MASW) and Ground Penetrating Radar (GPR) were the techniques used to characterize a waste dump in the town of Dąbrowa Górnicza (S Poland). GPR and SRT were the most difficult methods to use because of the dense vegetation, which attenuated the passage of electromagnetic and seismic waves to the ground. However, GPR did turn out to be an appropriate tool for characterizing variations in the surface cover. ERT, SRT and MASW clearly highlighted the transition between the waste deposit and the host sediments, and determined the approximate thickness of the waste deposits. With MASW, however, the waste type and the boundary between the waste layer and surface cover could not be delineated. In some places, the surface cover was identified using SRT. With both these methods, the problem with identification may be due to the small contrast in the S- and P-wave velocities through two kinds of waste (municipal and industrial), the thinness of the waste layer, and the considerable differentiation of the surface cover. The most accurate results regarding the waste deposits were obtained using ERT and different electrode spacings. ERT pinpointed the exact location of the stored waste, distinguished between the types of waste, and identified the soil cover. Data from shallow boreholes confirmed the interpretations of the methods.

Near-surface seismic refraction tomography and MASW for site characterization in Phuentsholing, Bhutan Himalaya

It is essential to understand the soil characteristics of the subsurface layers for any engineering construction. In difficult terrains like hilly areas, conventional methods of investigation are expensive and difficult to conduct. It calls for nondestructive testing methods to get reliable estimates of subsurface properties. In the present study, seismic refraction tomography (SRT) technique and multichannel analysis of surface waves (MASW) methods were carried out along five selected profiles in Phuentsholing region of Bhutan Himalaya. The profile length ranges from 37 to 81.5 m, and depth of imaging down to 10 m. While the SRT data imaged the P-wave velocity (Vp) structures, the MASW imaged the shear wave velocity (Vs) structures. The P-wave images provide a fair knowledge of geological layers, while the MASW images provide S-wave velocity structures (Vs). These results are useful to estimate soil parameters, like the density, Poisson’s ratio, Young’s modulus, shear modulus, N-value and the ultimate bearing capacity. The seismic images reveal the presence of sand, sandy clay, gravels and shale layers below the selected sites. Bhutan Himalayas being seismically vulnerable, the obtained results in terms of shear wave velocity were accustomed to categorize the sites as per NEHRP site classes, and a ground response analysis was performed to determine the reliable amplification factors. From the study, it is suggested that the engineering construction is feasible at all the sites except in one site, where an indication of saturated soil is observed which is vulnerable for liquefaction, and ground needs to be improved before construction at that site.

MASW for the microzonation of earthquake hazard in Banjar City, West Java, Indonesia

Efforts to reduce the impact of earthquake disaster have been made by the government, continuously. To decrease the casualties, an effort to be done is to construct housings and public infrastructures following the earthquake-resistant role or building code, especially in cities with high vulnerability and population. For this reason, an earthquake hazard microzonation map is crucial. Microzonation of earthquake hazard in Banjar City, West Java, Indonesia, was conducted by mapping the surface soil classification. Banjar is an essential city in West Java, connecting Bandung and the cities in the southern part. The microzonation mapping was done using the MASW (Multichannel Analysis of Surface Waves) method. The fieldwork of Vs30 measurements has been conducted in February 2020. We recorded 31 MASW sites in the entire Banjar City area with the distance between the locations approximately 5km. The results of this study indicate the surface soil classification in Banjar City in detail and precisely. The eastern part of the city shows a relatively softer surface soil structure compared to the western part. Comparison of the microzonation map obtained from the measurements with empirical Vs30 map (average shear waves velocity down to 30m), geology structure, and topographic data, showing good agreement. The earthquake microzonation map is recommended to be considered one of the references for developing the building code.

Local-scale phase velocity estimation using ambient seismic noise: comparison between passive seismic interferometry and conventional frequency–wavenumber methods

SUMMARYWe present a new processing scheme that uses passive seismic interferometry (PSI) followed by multichannel analysis of surface waves (MASW), which we call the 2-D PSI-MASW method, to obtain Rayleigh wave phase velocity dispersion (PVD) information. In this scheme, we first use the principles of PSI to form multidirectional cross-correlations (CCs) then project the CCs onto a 1-D virtual array and apply the phase-shift transform as in MASW processing. We compare PVD information obtained by this method with those of the conventional beam-power based frequency–wavenumber decomposition (CVFK) method using ambient seismic noise (ASN) data collected by local-scale 2-D arrays deployed at three selected sites in Bursa, Turkey. By analysing the ASN data from these sites, we show that similar multimodal PVD curves can be obtained with the two methods over a broad frequency range (∼2–23 Hz) within the wavenumber resolution and aliasing limits. However, in one of our sites where the 2-D array configuration has a considerable antisymmetry, we show that the 1-D virtual array used in the 2-D PSI-MASW method has a better array response function in terms of wavenumber resolution and suppression of side-lobes leading to superior mode resolution and separation than that of the CVFK method, which shows strong directional variations. Furthermore, unlike the CVFK method, the 2-D PSI-MASW method takes advantage of temporal stacking of CCs ensuring weak but coherent Rayleigh wave signals present in the ASN wavefield to be strengthened and has the potential for better extraction of PVD information. We conclude that by using a 2-D array with spatial coverage providing a wide range of directions and distances, reliable PVD information can be obtained even if the ASN sources are not concentrated in the stationary phase zones. Thus, we suggest that the 2-D PSI-MASW method is highly advantageous for the extraction of reliable PVD information owing to the multidirectional CCs provided by the 2-D array configurations. We also report that using only a single receiver line in the interferometric approach results in biased and/or incomplete PVD information due to the non-isotropic ASN source distribution at all three sites we analysed. In conclusion, our results clearly indicate that the 2-D PSI-MASW method can be used as complementary or alternative to the CVFK method to extract multimodal Rayleigh wave PVD information in local-scale seismological studies.

Advantages of Geophysics to Improve Site Characterization and Reliability for Transportation Projects

Under the Federal Highway Administration’s innovation development program “Every Day Counts” (EDC-5), the initiative on Advanced Geotechnical Methods in Exploration (A-GaME) aims to improve the knowledge in U.S. practice on existing but underutilized subsurface exploration methods. The A-GaME suite of technologies is a group of proven and effective exploration technologies and practices that, in conjunction with limited conventional exploration methods, mitigate the risks of geotechnical uncertainties and optimize subsurface exploration programs for improved site characterization and reliability over a wider coverage area and maximum return-on-investment. Transportation agencies are becoming more eager to employ alternative exploration methods to supplement their investigations and limit uncertainty emanating from geotechnical subsurface conditions. In this context, Arkansas Department of Transportation, in collaboration with the University of Arkansas, has implemented geophysical methods in subsurface investigation to acquire adequate information in relation to bedrock depth and rippability for new construction and to address slope stability issues along roadways. Different geophysical methods have been employed, including multichannel analysis of surface waves (MASW), electrical resistivity tomography (ERT), and microtremor horizontal to vertical spectral ratio (MHVSR). Two case studies are presented here, one for a proposed and one for an existing transportation project. According to the results of these case histories, the joint application of MASW and MHVSR was determined to be valuable for rock rippability estimates for roadway projects, whereas the combined use of MASW, MHVSR, and ERT produced significant additional subsurface information for landslide assessments and remediation efforts.

Detection of a shallow-buried rock obstruction using 2D full waveform inversion

Shallow-buried rock mass/obstructions in a reclaimed sand site have seriously delayed a construction project in eastern Singapore, and seismic surveys were conducted to estimate the location and range of the rock. Active-source and passive-source seismic data were recorded using an array with 24 geophones at 1 m intervals. A 2D full waveform inversion (FWI) approach, multichannel analysis of surface waves (MASW), and cross-correlation seismic interferometry were used to process the collected seismic data. Results show that MASW and cross-correlation provide useful information, but limited to 1D S-wave velocity profiles and the upper surface of shallow buried rock. Using the full information of seismic waveform, the FWI approach can reflect even the range of rock. Sequential inversion with a low-pass frequency filter at incremental corner frequencies can increase the precision of the FWI approach. With higher precision, the FWI of surface waves is considered to be an attractive and effective method to detect underground obstruction.

Multiwindow weighted stacking of surface-wave dispersion

Surface-wave methods are classically used to characterize shear (S-) wave velocities ([Formula: see text]) of the shallow subsurface through the inversion of dispersion curves. When targeting 2D shallow structures with sharp lateral heterogeneity, windowing and stacking techniques can be implemented to provide a better description of [Formula: see text] lateral variations. These techniques, however, suffer from the trade-off between lateral resolution and depth of investigation (DOI), which is well-known when using the multichannel analysis of surface waves (MASW) method. We have adopted a novel methodology aimed at enhancing lateral resolution and DOI of MASW results through the use of multiwindow weighted stacking of surface waves (MW-WSSW). MW-WSSW consists of stacking dispersion images obtained from data segments of different sizes, with a wavelength-based weight that depends on the aperture of the data selection window. In that sense, MW-WSSW provides additional weight to short wavelengths in smaller windows so as to better inform shallow parts of the subsurface, and vice versa for deeper velocities. Using multiple windows improves the DOI, whereas applying wavelength-based weights enhances the shallow lateral resolution. MW-WSSW was implemented within the open-source package SWIP and applied to the processing of synthetic and real data sets. In both cases, we compared it with standard windowing and stacking procedures that are already implemented in SWIP. MW-WSSW provided convincing results with optimized lateral extent, improved shallow resolution, and increased DOI.

Estimating the Small Strain Stiffness of Peat Soil Using Geophysical Methods

Geotechnical design commonly requires that the in-situ stiffness, strength and permeability of the ground be obtained. Laboratory based investigation often related with risk of sample disturbance and difficulties to replicate the in-situ stress condition which results in overestimation or underestimation. Application of geophysical methods in geotechnical investigation previously was limited to targeting and dimensioning sub-surface features due to lack of resolution. However, rapid developments of geophysical methods result in the application of these methods in providing geotechnical design parameters. Multichannel analysis of surface waves (MASW) and seismic refraction were among the geophysical methods capable of obtaining stiffness parameters including the maximum shear modulus (Gmax) and maximum elastic modulus (Emax). The study revealed the efficiency of these methods to measure the small strain stiffness of peat soil with high accuracy as the results obtained were found to be similar to those obtained by previous researchers. Overall, the Gmax and Emax values of peat soil obtained range from 0.49 to 1.72 MPa and 1.46 to 5.15 MPa respectively. The Gmax and Emax values obtained shows significant increase with depth governed primarily by the effective stress. Other parameters such as degree of decomposition and peat thickness also shows potential influence on the Gmax and Emax values obtained.