Multichannel Analysis Of Surface Waves Data Research Articles

Subsurface Characterization of Malaysian Hemic Peat and Soft Clays Using CPTu and MASW

Geotechnical engineers practice a variety of in-situ investigation techniques to comprehensively characterize peat soil properties. Peat soil is a challenging soil characterized by its high water content, organic content, and low strength, making its geotechnical properties difficult to assess accurately. High water saturation and the presence of fresh fibres in peat also risk sample disturbance in collecting undisturbed peat soil samples which causes underestimation. An In-situ test known as the Cone penetration test with pore pressure measurement (CPTu) was investigated to measure the cone resistance (qc), sleeve friction (fs), and pore water pressure (u2) at various depths. In parallel, multichannel analysis of surface waves (MASW) was employed to determine the shear wave velocity (Vs) profile of the peat soil. The findings revealed that CPTu and MASW data were able to delineate the soil stratigraphy and estimate the peat thickness. However, the presence of fresh fibres in peat causes overestimation of the qc and fs values, causing difficulties in accurately determining the peat strength. Overall, the combination of CPTu and MASW data offered a comprehensive understanding of the peat’s geotechnical and dynamic characteristics. The findings have significant implications for engineering practices and ultimately contribute to safer and more resilient construction projects in challenging peat soil environments.

Detecting mechanical property anomalies along railway earthworks by Bayesian appraisal of MASW data

The techniques traditionally used to estimate the mechanical properties of railway earthworks (RE) are costly and of low performance. There is a great need for the development of non-destructive methods, which would allow a fast and efficient diagnosis of RE. Seismic surface-wave (SW) methods, also known as multi-channel analysis of surface waves (MASW), were rescaled here for there systematic implementation on RE. A test site was chosen along the North European High Speed Line (HSL) for its well-known correspondence between discontinuity in mechanical properties and anomalous maintenance forces. With the proposed acquisition and processing strategy, a contrast in SW propagation velocity was correlated with the change in shear modulus of the soil layers beneath the track, previously evaluated in the laboratory. Bayesian inversion of the SW data also allowed to integrate the strong a priori knowledge available on these HSL lines and to provide quantitative results with a confidence index to help end-users in their decisions.

Seismic site characterization using MASW and correlation study between shear wave velocity and SPT[sbnd

A seismic site characterization study is carried out in the south of the foothills of tectonically active Himalayan region. During an earthquake, the dynamic characteristics of the shallow subsurface strata can influence seismic shaking in the region, causing damage to civil infrastructures. The seismic site characterization study with shear wave velocity (Vs) is performed using the Multi-channel Analysis of Surface Wave (MASW) technique, which is particularly challenging to implement in the densely inhabited areas. However, the standard penetration test (SPTN) commonly measured by civil engineers can be utilized to compute Vs of such areas by establishing a correlation between Vs and the SPT-N values.In the study area, MASW data were acquired at twelve different locations, whereas SPT-N tests were available from 26 boreholes. Twelve borehole locations closer to the MASW survey lines were paired to establish relationships between SPT-N and Vs. The developed linear and non-linear correlation functions were found to be statistically similar. Furthermore, the linear correlation function is used for estimating Vs from SPT-N in remaining 14 boreholes. The new correlation functions were further compared with previously reported empirical relationships from other areas. The current relationship can be used for geoengineering purposes at different sites with similar geological conditions.Shear wave velocity derived from the MASW surveys and estimated from the new empirical relationship was utilized for seismic site characterization based on average shear wave velocity up to 30 m depth (Vs30). The Vs30 map of the study site is prepared and classified in accordance with the National Earthquake Hazard Reduction Program (NEHRP-2020). The calculated Vs30 value of the study site ranges from 285 to 375 m/s. The major portion of the study area lies under Site Class CD, with a minor portion under Site Class D. In the event of an earthquake, some zones can potentially have stronger ground amplification, particularly in Site Class D and may have damaging effects. A series of average shear wave velocity maps for different depths are prepared to help geotechnical engineers in identifying and mitigating geotechnical risks. Furthermore, there are potential geohazard risks as certain depths show low shear velocity.

Identification of re-liquefaction potential based SPT and MASW data in Mpanau, Sigi after the earthquake 2018

In September 2018, there was an earthquake followed by liquefaction which caused damage to thousands of houses and infrastructure in Central Sulawesi Province, Indonesia. Liquefaction in Central Sulawesi has the potential to recur, so identifying potential liquefaction in areas that have occurred is essential. The objective of this research is to compare the results of determining liquefaction potential based on geotechnical and geophysical data. Based on the peak ground acceleration earthquake value, it shows that the liquefaction potential obtained in Mpanau is resemblant. The simulation will be conducted using Settle3 software based on methods, then the values of Cyclic Resistance Ratio (CRR) and Cyclic Stress Ratio (CSR) will be compared based on existing Multi-Channel Analysis of Surface Waves (MASW) data. MASW needs to be considered in the way of potential identification because it is advantageous. This Research uses MASW data where liquefaction flow and damage do not occur in Mpanau area even though the potential is quite significant. The result of this research shows that at distinct points of the SPT, MASW and the 7.5 Mw earthquake resulted in potential liquefaction still present in several soil layers, especially in the Gumbasa canal. It is necessary to repair and countermeasure to prevent liquefaction from disrupting the irrigation system's performance.

Determination of Seismic Site Class and Potential Geologic Hazards using Multi-Channel Analysis of Surface Waves(MASW) at the Industrial City of Abu Dhabi, UAE

ABSTRACT Geophysical investigation activities were conducted at ICAD-II, Abu Dhabi, UAE using Multi-Channel Analysis of Surface Waves (MASW) to determine subsurface geology , material stiffness, potential weak zones down to ~35 m depth, and to propose the appropriate seismic site classification for a proper foundation design. A total of 20 MASW lines were carried out over a grid layout of 5 m spacing. Data acquisition, processing and inversion have been parameterised and selected to produce shear velocities that represent subsurface conditions. The estimated average shear-wavevelocity (Vs30 = 577.97 m/s) suggests that the investigated site can be classified as Class C (V.D. Soil & Soft Rock). The constructed geological model comprises sand, weak sandstone, weak mudstone, and hard mudstone. Analysing the shear wave velocities indicates the absence of apparent cavities/ hazardous zone . However, a relatively weak layer of sandstone/mudstone rocks intercalations was detected from ~7m to ~25m. Meanwhile, the uncorrelated part of 2D MASW data indicates potentially harder mudstone encountered at a depth starting from ~25 m to >35 m. Hence, the foundation layer may be placed on the upper surface of the sandstone bed (~7 m) depending on the height and load of the proposed building and following the construction standards and requirements of the structural engineer.

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.

Salt layer characteristics in the Ghor Al-Haditha area, Jordan: comprehensive combined reprocessing of geophysical data

The presence of buried salt layer in the Ghor Al-Haditha area is discussed concerning sinkhole hazard. Numerous geophysical methods such as seismic refraction (SRFR), reflection (SRFL), seismic tomography, multichannel analysis of surface waves (MASW) were developed earlier for the salt layer identification. Geophysical criteria of salt parameters (such as longitudinal Vp and shear Vs wave velocities) were established to identify salt layers. This paper presents new geophysical results proving the salt extension in the Dead Sea (DS) coastal area in its eastern shore potentially representing a sinkhole hazard. The reprocessing technique of MASW data using the synthetic modeling enabled us to detect salt layer characteristics such as depth to its top, the thickness of the layer, and its Vs velocity. It was established that a salt layer with 7–10 m thick is located at a depth of 37–41 m and is characterized by shear-wave velocity (Vs) of 850–1200 m/s. Similar results were obtained by the Transient Electromagnetic (TEM) resistivity method, which detected a comparatively resistive salt layer at a background of very low resistivity. The resolution of the TEM method allows detecting a salt layer of 3 m thick and more at a depth of 39–40 m. Seismic refraction data processing has shown the presence of a salt layer with a velocity of more than 2900 m/s at approximately or the same depths. Analysis of seismic tomography data also confirms the parameters of the discovered target. Analysis of results of geophysical studies in the western and eastern DS shores, comparison of geological conditions in shores, and sinkhole development, enabled us to conclude with a high probability that salt layers exist in both shores and sinkhole development is determined here by similar mechanisms.

Integrated approach for the MASW dispersion analysis using the spectral element technique and trust region reflective method

Abstract In this paper, a semi-analytical elastodynamic forward solver was proposed for the Multichannel Analysis of Surface Waves (MASW) using the spectral element technique for the first time. A root finding method based on Brent's algorithm was proposed to accurately extract the dispersion curves. The trust region reflective method, an effective bound-supported least square algorithm, was applied, for the first time, for the inversion analysis of MASW data. In comparison to the commonly used neighborhood algorithm, the proposed solver converges rapidly; the Euclidean distance between the measured and numerically calculated dispersion curves are significantly reduced within only 300 runs of the forward solver in comparison to over 10,000 runs using the neighborhood algorithm. Several numerical case studies were performed to demonstrate the selection of initial guesses as well as the bounds of each optimization parameter. Also, a parametric study was performed to determine the effect of discontinuity in the soil stratigraphy on the dispersion curves. Finally, the integrated approach developed in this study was used to analyze the MASW data collected in a site in south Iceland. It was concluded that the proposed approach determines effectively and efficiently the soil stratigraphy as well as soil properties.

Combined use of refraction seismic, MASW, and ambient noise array measurements to determine the near-surface velocity structure in the Selinunte Archaeological Park, SW Sicily

Seismic refraction, multichannel analysis of surface waves (MASW) and ambient noise array measurements using the wireless array analysis (WARAN) system were applied to acquire near-surface profiles of seismic velocities in the Selinunte Archaeological Park. This ancient city is famous for numerous temples, which according to the literature, were destroyed by at least two earthquakes in antiquity. The morphology of the archeological park is affected by two rivers which in combination with the temple remains suggests three study sites. We determined the subsurface velocity at these three locations as essential information for further studies of the response of the temple structures to earthquake ground motions. The stratigraphy of the site indicates that low-velocity layers might exist. Seismic refraction profiles with 69 m spread and 24 geophones were employed during the active seismic experiments. The measured P-wave velocities of the top two layers were used as a constraint during the inversion of dispersion relations from the MASW and WARAN data. The reliability of the velocity profiles was tested by forward calculation of synthetic seismograms. P-wave velocities which were not well constraint throughout the dispersion curve inversions were adjusted through suitable Poisson’s ratios based on the well constraint S-velocities. The combined use of the three different kinds of measurements and multi-mode interpretation of the dispersion curves revealed velocity profiles including low-velocity layers which are supported by de-amplification observed in ratios of horizontal and vertical components of noise spectra.

In Situ Shear Wave Velocity From Multichannel Analysis of Surface Waves (MASW) Tests at Six Sites of Delhi Technological University

In the mid-1980s, the surface wave method was initially exhibited as an instrument for the geotechnical engineering field. This non-obtrusive seismic method of multi-channel examination of surface waves is prominently used to draw out the shear-wave velocity profile (variation of soil with respect to its depth). In an attempt to increase the sureness in the construed shear wave velocity (Vs) profile as a result of the ambiguity in the analysed dispersion characteristics, the multichannel method is used in this research to characterize six test sites on the campus of Delhi Technological University, Delhi. The multi-channel analysis of surface waves (MASW) method commenced from the traditional seismic survey method that engages twenty-four receivers positioned all along a linear survey track. The current study implies results from MASW survey at six sites within the DTU campus, for which the MASW data acquisition comprise of the use of a 24-channel PASI seismograph and 24 numbers of 4.5 Hz Vertical geo-phones set apart at 2 m each and source offset (2 m,4 m). The seismic power source was a steel sledgehammer (15 lbs). In order to develop and invert the surface-wave seismic data in addition to creating the one-dimensional depth versus Shear Wave Velocity (Vs) profiles WinMasw software was used. The mean shear wave velocity of the current study area is 285 m/sec. The mean shear wave velocity for Delhi city is in a range of 110 to 350 m/s.

High-Velocity Surface Layer Effects on Rayleigh Waves: Recommendations for Improved Shear-Wave Velocity Modeling

ABSTRACTSoil 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.

Seismic microzonation maps of Phrae city, Northern Thailand

A case study using shear wave velocity (Vs) data obtained from seismic multi-channel analysis of surface wave (MASW) studies was used to evaluate site conditions in Phrae City, Northern Thailand. The MASW data was acquired at 40 sites that covered the entire city area. The main goal was to generate seismic microzonation maps for Phrae City. The NEHRP map generated from the Vs data closely matched the surficial geological map. Areas mapped as alluvium soil were assigned to NEHRP soil class D, while areas mapped as colluvium and river terrace soils, in contrast, fell into the NEHRP soil class C. The amplification map indicated a higher amplification in the west and central part of the city, where the soils mostly consisted of soft sediments from alluvial deposits. The eastern study area had a relatively low amplification, because the sediments in this area mostly consisted of coarse grain sediments. The site period map revealed that three- to four-story buildings were likely to be susceptible to ground shaking in most parts of the city, whereas one- to two-story buildings were only vulnerable in the eastern part of the study area.

Characterisation of ground motion recording stations in the Groningen gas field

The seismic hazard and risk analysis for the onshore Groningen gas field requires information about local soil properties, in particular shear-wave velocity (VS). A fieldwork campaign was conducted at 18 surface accelerograph stations of the monitoring network. The subsurface in the region consists of unconsolidated sediments and is heterogeneous in composition and properties. A range of different methods was applied to acquire in situ VS values to a target depth of at least 30 m. The techniques include seismic cone penetration tests (SCPT) with varying source offsets, multichannel analysis of surface waves (MASW) on Rayleigh waves with different processing approaches, microtremor array, cross-hole tomography and suspension P-S logging. The offset SCPT, cross-hole tomography and common midpoint cross-correlation (CMPcc) processing of MASW data all revealed lateral variations on length scales of several to tens of metres in this geological setting. SCPTs resulted in very detailed VS profiles with depth, but represent point measurements in a heterogeneous environment. The MASW results represent VS information on a larger spatial scale and smooth some of the heterogeneity encountered at the sites. The combination of MASW and SCPT proved to be a powerful and cost-effective approach in determining representative VS profiles at the accelerograph station sites. The measured VS profiles correspond well with the modelled profiles and they significantly enhance the ground motion model derivation. The similarity between the theoretical transfer function from the VS profile and the observed amplification from vertical array stations is also excellent.

Assessment of Liquefaction Potential of Some Coastal Soils in Lagos, South-Western Nigeria Using Geophysical and Geotechnical Methods

Liquefaction occurs in shallow, loose, saturated deposits of cohesionless soils subjected to strong shearing stresses. This leads to the transfer of stress from the soil skeleton to the pore water precipitating a decrease in effective stress and shear resistance of the soil. The study gives the results of the liquefaction potential assessment in some part of Lagos wetland areas of Lagos. The aim of this study was to assess the liquefaction potential through the evaluation of its severity in response to Earth tremors. In order to achieve this purpose, Multi-channel Analysis of Surface waves (MASW) and Cone penetration testing (CPT) were carried out. For an optimal coverage of the study area, twenty-four channels 4.5Hz geophones connected to the ABEM Mark 6 Seismograph through two cable reels were used to detect the generated seismic wave produced by the weight drop of about 19.1 kg. The CPT soundings for assessing subsurface stratigraphy with respect to liquefiable soils were carried out with a 10-Ton Dutch Cone Penetrometer. The softwares used were SeisImager, for processing the MASW data and CLiq for the CPT measurements. The shear wave velocity models were generated for the MASW measurements. The models show that sand sediments with velocity ranging from 118 - 279 m/s dominated most of the study area. Also, the results show that for the potential liquefiable sands identified, the shear wave velocity ranges between 118.0 – 180 m/s delineated at depths between 10.0 – 20.0 m within study profile an is typical of liquefiable sands. Simplified procedure of assessment of Liquefaction potential from CPT showed a model curve whereby some CPT points were within the liquefiable zones.

Multichannel analysis of the surface waves of earth materials in some parts of Lagos State, Nigeria

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.

The Simple Lamb Wave Analysis to Characterize Concrete Wide Beams by the Practical MASW Test.

In recent years, the Lamb wave analysis by the multi-channel analysis of surface waves (MASW) for concrete structures has been an effective nondestructive evaluation, such as the condition assessment and dimension identification by the elastic wave velocities and their reflections from boundaries. This study proposes an effective Lamb wave analysis by the practical application of MASW to concrete wide beams in an easy and simple manner in order to identify the dimension and elastic wave velocity (R-wave) for the condition assessment (e.g., the estimation of elastic properties). This is done by identifying the zero-order antisymmetric (A0) and first-order symmetric (S1) modes among multimodal Lamb waves. The MASW data were collected on eight concrete wide beams and compared to the actual depth and to the pressure (P-) wave velocities collected for the same specimen. Information is extracted from multimodal Lamb wave dispersion curves to obtain the elastic stiffness parameters and the thickness of the concrete structures. Due to the simple and cost-effective procedure associated with the MASW processing technique, the characteristics of several fundamental modes in the experimental Lamb wave dispersion curves could be measured. Available reference data are in good agreement with the parameters that were determined by our analysis scheme.

A Comparison of Surface- and Standard Penetration Test-Derived Shear-Wave Velocity

Shear wave velocity ( V s ) values calculated from Standard Penetration Tests (SPTs) and from multi-channel analysis of surface waves (MASW) are consistent in their prediction of V s . This analysis was based upon SPT and MASW data from 10 localities representing four different depositional environments across North America. Homogeneous deposits tend to produce the closest agreement between MASW- and SPT-derived V s . Poorly sorted deposits can predict less consistent agreement between MASW- and SPT-derived V s . Further, at depths of greater than 20 m below grade, based upon the testing geometry within this work, the prediction of V s between the two methods can differ.

ERT-based Investigation of a Sinkhole in Greene County, Missouri

Investigating sinkhole morphology and formation mechanisms is key to understanding their long term impact and susceptibility to development, and aids in the design of effective mitigation measures. In this study, ERT (electrical resistivity tomography), MASW (multichannel analysis of surface waves) and borehole data were used to image the subsurface morphology of an active sinkhole in Greene County, Missouri. The study reveals that the sinkhole developed along a natural surface drainage pathway above a pervasively fractured limestone. The subsurface image of the sinkhole depicts a zone of near-vertical water seepage and soil piping. Based on the nature of the overburden material, and the morphology and current/past surface expression of the sinkhole, it is concluded that the sinkhole is predominantly a cover subsidence type of sinkhole. However, it is possible that minor cover collapse occurred locally and in an area slightly to the north of the current active sinkhole.

ERT-based Investigation of a Sinkhole in Greene County, Missouri

Investigating sinkhole morphology and formation mechanisms is key to understanding their long term impact and susceptibility to development, and aids in the design of effective mitigation measures. In this study, ERT (electrical resistivity tomography), MASW (multichannel analysis of surface waves) and borehole data were used to image the subsurface morphology of an active sinkhole in Greene County, Missouri. The study reveals that the sinkhole developed along a natural surface drainage pathway above a pervasively fractured limestone. The subsurface image of the sinkhole depicts a zone of near-vertical water seepage and soil piping. Based on the nature of the overburden material, and the morphology and current/past surface expression of the sinkhole, it is concluded that the sinkhole is predominantly a cover subsidence type of sinkhole. However, it is possible that minor cover collapse occurred locally and in an area slightly to the north of the current active sinkhole.

Comparison of MASW and MSOR for Surface Wave Testing of Pavements

This paper presents a computational and experimental study on seismic stiffness profiling of layered pavement systems using the multi-channel analysis of surface waves (MASW) and multi-channel simulation with one receiver (MSOR) testing procedures. Development of a new custom-programmed data acquisition system for MASW and MSOR testing using MATLAB software and National Instruments hardware are detailed. A receiver coupling method is presented, which was found to perform the best among several methods examined by the authors. The cross-correlation function is employed to statistically quantify the repeatability of impacts, which is critical for MSOR tests in which multi-channel records are simulated by performing multiple impacts over a range of incremental offsets from a single fixed receiver. Experimental dispersion data from MASW and MSOR tests performed at the same asphalt pavement site with the same testing system are compared, and MASW is found to enable measurement of dispersion data to much higher frequencies using the authors’ methods than MSOR. Inversion results from the MASW and MSOR data at the same asphalt pavement site also are compared, and it is found that MASW is able to provide measurements of the stiffness of the pavement surface layer with reduced variability.