Surface Wave Survey Research Articles

Detection of Beaded Karst Caves in Subway Works by Mixed-Source Surface Wave Survey: A Case Study

Abstract Karst cave causes geological disasters in tunneling engineering, which brings great risks to subway construction. The microtremor survey has become one of the main methods for karst cave detection in urban areas due to its convenience and great detection depth. However, the microtremor survey lacks high-frequency signals, resulting in poor detection accuracy on the shallow layer. An advanced method called mixed-source surface wave (MSW) method is proposed by imposing active sources during the continuous passive surface wave survey. MSW is applied to the detection of beaded karst caves (i.e. two or three karst caves at different depths in the same location) in Ji'nan, China. The influences of ambient noise, array type, and other factors on the detection accuracy were studied. Experimental results show that the detection depth and accuracy of MSW are much better than those of passive surface wave method. The inversion accuracy of linear array perpendicular to road is better than the triangle array and L-shaped array. The accuracy of the linear array along the road is worst. The detection accuracy of MSW is similar to that of combined active–passive surface wave methods. However, the basic principle of MSW is easier to understand, and its operation is more convenient. The two-dimensional measurement results show that the MSW method can well reflect the size and location of the beaded karst cave and provide important references for the practical engineering.

Detection of the low-velocity layer using a convolutional neural network on passive surface-wave data: An application in Hangzhou, China

Passive surface-wave methods using dense seismic arrays have gained growing attention in near-surface high-resolution imaging in urban environments. Deep learning (DL) in the extraction of dispersion curves and inversion can release a tremendous workload brought by dense seismic arrays. We presented a case study of imaging shear-wave velocity (Vs) structure and detecting low-velocity layer (LVL) in the Hangzhou urban area (eastern China). We used traffic-induced passive surface-wave data recorded by dense linear arrays. We extracted phase-velocity dispersion curves from noise recordings using seismic interferometry and multichannel analysis of surface waves. We adopted a convolutional neural network to estimate near-surface Vs models by inverting Rayleigh-wave fundamental-mode phase velocities. To improve the accuracy of the inversion, we utilized the sensitivities to weight the loss function. The average root mean square error from the weighted inversion is 46% lower than that from the unweighted DL inversion. The estimated pseudo-2D Vs profiles correspond to the velocities obtained from downhole seismic measurements. Compared with an investigation on the same survey area, our inversion results are more consistent with the Vs provided by downhole seismic measurements within 50–60 m where the LVL exists. The trained neural network successfully identified that the LVL is located at 50–60 m deep. To check the applicability of the trained neural network, we applied it to a nearby passive surface-wave survey and the inversion results agree with the existing investigation results. The two applications demonstrate the accuracy and efficiency of delineating near-surface Vs structures with the LVL from traffic-induced noise using the DL technique. The DL inversion has great potential for monitoring subsurface medium changes in urban areas.

Distributed acoustic sensing for seismic surface wave data acquisition in an intertidal environment

The application of distributed acoustic sensing (DAS) for shallow marine seismic investigations is assessed, in particular with respect to the collection of seismic surface wave data in an intertidal setting. Appropriate selection and directional sensitivity of fiber-optic cables is considered and the measured data is validated with respect to conventional seismic data acquisition approaches, using geophones and hydrophones, along with independent borehole and seismic cone penetration test (SCPT) data. In terms of cable selection, a reduction in amplitude and frequency response of an armored cable is observed, when compared with an unarmored cable. For seismic surface wave surveys in an offshore environment where the cable would need to withstand significant stresses, the use of the armored variant with limited loss in frequency response may be acceptable from a practical perspective. The DAS approach also has indicated good consistency with conventional means of surface wave data acquisition, and the inverted [Formula: see text] also is very consistent with downhole SCPT data. Observed differences in phase velocity between high tide (Scholte wave propagation) and low tide (Rayleigh wave propagation) are not thought to be related to the particular type of interface wave due to shallow water depth. These differences are more likely to be related to the development of capillary forces in the partially saturated granular medium at low tide. Overall, this study demonstrates that our novel approach of DAS using seabed fiber-optic cables in the intertidal environment is capable of rapidly providing near-surface S-wave velocity data across considerable spatial scales (multikilometer) at high resolution, which is beneficial for the design of subsea cables routes and landfall locations. The associated reduction in deployment and survey duration, when compared with conventional approaches, is particularly important when working in the marine environment due to potentially short weather windows and expensive downtime.

Analysis of the shear wave velocity structure of a soft-hard interlayered rock slope based on surface wave and microtremor survey

The information regarding the layered structure is pivotal to the stability analysis of soft-hard interlayered rock slopes. The variation in the shear wave velocity offers insights into the characteristics of the strata structure within a rock slope. In this study, a joint analysis method that combines the multichannel analysis of surface waves (MASW) and the microtremor surface method (MSM) was used to identify the layered structure of a soft-hard interlayered rock slope located in the Shandong Province, China. The survey lines were positioned on slope crests. For the MASW, the receivers were placed in line with an active seismic source. The MSM method uses a concentric circular array comprising seven receivers. Fundamental-mode dispersion data were extracted from the active and passive microtremor sources. The 1D velocity models were then inverted from the combined dispersion curves using a surrogate optimization algorithm. A 2D velocity profile of the investigated slope was constructed through linear interpolation, and it exhibited distinct characteristics of high- and low-velocity interlayers, consistent with the borehole data. Our results demonstrate that the joint analysis method provides a complementary approach to image velocity profiling of slopes, thus contributing to enhanced investigation depth and resolution in shallow layers owing to the wider frequency range of the dispersion curves.

Relation Between Soil Profiles and Surface-Wave Survey Results for a Weathered Rhyolite Slope in Hiroshima, Japan

Relation Between Soil Profiles and Surface-Wave Survey Results for a Weathered Rhyolite Slope in Hiroshima, Japan

Effect Analysis on Field Acquisition Parameters of Surface Wave Survey - Case Study on The Gobi Desert Field

In this paper, the Gobi Desert landform is used as a test site to analysis the results on surface wave survey. The body wave exploration methods are used to determined velocity structure of the site as a reference standard firstly. Subsequently, different acquisition parameters for surface wave are tested. After comparing the results, the optimal parameters are selected by using the surface wave multi-channel analysis method (MASW). Meanwhile, several theoretical equations for estimating minimum offset, optimum offset, geophone spread length, and resolution of dispersion are demonstrated as the guidelines to organize the real-world data acquisition. Finally, the selected optimal parameters are applied to the data acquisition of total 69 surface wave recorders. The final two-dimensional inversion profile is in good agreement with the known background. It means the method of MASW is feasible in geological surveys on Gobi Desert landform.

Linear array analysis of passive surface waves combined with mini-Sosie technique

SUMMARY Mini-Sosie, which is convenient and environmentally friendly with high energy output, is gaining increasing attention as a seismic exploration source. Passive surface wave survey using ambient noise have become a powerful tool for exploration in urban areas due to the advantages of being efficient and non-destructive. A 2-D or pseudo-1D array that can attenuate phase velocity overestimation due to directional noise are the optimal choice, but such arrays are limited by the complex environment of the experimental site on the one hand and the need to ensure that the medium beneath the array meets the assumption of lateral isotropy on the other. However, the fully 1-D linear array as an alternative lacks the ability to suppress the directional effect of the noise source. In this study, we develop a novel approach for linear array analysis of passive surface waves combined with mini-Sosie technique, called LAPSS. We use the mini-Sosie technique with fixed-frequency impact in the in-line direction to provide the theoretical phase velocity values at several frequency points as a reference for the biased dispersion image obtained from the linear array analysis, so as to estimate the azimuth of the noise source and to perform the correction of the biased dispersion image. We present the detailed workflow of LAPSS and compare the performance of LAPSS with PLAS (which has proven to be superior to the frequency–wavenumber method, spatial autocorrelation method, refraction microtremor and multichannel analysis of passive surface waves) in achieving unbiased dispersion image with different noise source distributions through synthetic tests. The results show that the accuracy of the two methods is comparable, but LAPSS greatly improves the computational efficiency, has stronger generalizability and depends on weaker assumptions. Finally, a field experiment is conducted to verify the feasibility and effectiveness of LAPSS in obtaining unbiased dispersion images using a fully linear array.

Application of Multi-Channel Analysis Surface Waves and Electrical Resistivity Tomography Methods to Identify Weak Zones at University of Mosul, Northern Iraq

Cracks have been developed in a large lecture hall on the University of Mosul Campus. These cracks exist along two sides of the building. Multi Analysis Surface Wave and Electrical Resistivity Tomography surveys were conducted at the surrounding building to investigate the nature and distribution of shallow subsurface soil/rock. The MASW’s data show three layers: the first layer is characterized by low shear wave velocity ranges between 210 and 420 m/s which is attributed to infill materials, the next layer is attributed to a river terrace (fairly competent rock) which has Vs ranging from 430m/s to 840 m/s. It is recognized by a gradual increase in mechanical characteristics as depth increases. In-depth between about 2.5m and 6.0 m the shear wave velocity drops in the top contact of this layer. The causes of low velocity may be due to weathering of the medium because of a sinkhole. The Electrical Resistivity Tomography profile shows four electrical zones, the first zone has 50-70 Ω.m. with a variable thickness from 0.5-1.5 m which indicates infill materials. The second zone has very low resistivity value, and a depth ranges 0.5m - 3.5 m, which might be interpreted to be increased clay, silt and water content (high water-saturated zone). The third zone is characterized by a high-resistivity value (>100 Ω.m) that could be related to a dry conglomerate rock and gravels belong to river terraces. The fourth zone has a low-resistivity value (<20 Ω.m) associated with a water-saturated marl bed. We could be definitively correlated the resistivity and velocity anomalies to sinkhole activity in were identified and characterized using combined geophysical methods. The Multi Analysis Surface Waves and Electrical Resistivity Tomography were shown to complete each other in the evaluation. The variations in Vs (low velocity) and resistivity (conductive zone) within the river terrace were detected and proposed to be indicative of dissolution and the subsidence responsible for structural damage implied by the change in the velocity and resistivity. The roughness of the top terrace surface strongly influences the nature of the velocity and resistivity values. This roughness is suggestive of dissolution or erosion.

Determination of near-surface shear-velocity structure based on the joint inversion of Rayleigh-wave dispersion and ellipticity from multistation active-seismic records

The dispersive characteristics of high-frequency (≥2 Hz) Rayleigh waves have been widely applied to determine subsurface shear velocity ([Formula: see text]). However, the [Formula: see text] of the high-velocity surface layers (e.g., rigid roads in urban areas) and underlying layers is poorly constrained in the Rayleigh-wave dispersion inversion. Compared to the phase velocity, the Rayleigh-wave horizontal-to-vertical (H/V) ratios of particle motion (i.e., ellipticity) are particularly sensitive to shallow [Formula: see text] structures. Therefore, we have proposed a robust method for obtaining near-surface [Formula: see text] structures by inverting Rayleigh-wave dispersion and H/V data. Initially, we separate the fundamental-mode Rayleigh waves from the active-seismic records using a high-resolution linear Radon transformation method. Then, we extract the high-frequency H/V and interstation phase traveltimes from the separated fundamental mode using deconvolution interferometry and the frequency-time analysis method. Based on the phase traveltimes, we calculate the phase velocity dispersion using ray-based tomography. Finally, we perform the joint inversion of dispersion and H/V data to obtain the [Formula: see text] structure. According to the inversion results of synthetic and field data, the accuracy of the [Formula: see text] in the rigid surface layer and underlying layers is considerably improved. We find that the joint inversion of Rayleigh-wave phase velocity dispersion and H/V data from surface-wave surveys is a useful tool for accurately determining the complex shallow [Formula: see text] structures.

Application of multichannel analysis of passive surface waves method for fault investigation

Research on faulting is of fundamental significance to the exploration of geothermal resources since faulting is an important factor in the formation of traps for water accumulation. The high-frequency passive surface waves methods using ambient noise data become more popular because of its low-cost, environment-friendly, non-destructive and efficient advantages. We have conducted a field work in Hetian town of Zhejiang Province to evaluate the feasibility of high-frequency passive surface wave survey for fault investigation. We adopted the multichannel analysis of passive surface waves (MAPS) to process the high-frequency (>1 Hz) ambient noise for retrieving surface waves. Spectral analysis indicated that the dominant energy of ambient noise is focused on the frequency band from 1 to 12 Hz. We utilized the beamforming technique to show the distribution of ambient noise energy and the stable phase-velocity range of plane wave and reveal the location of interior sources in the receiver array. We selected these segments with less interior-source contamination from noise data collected at night to obtain clear and continuous surface-wave dispersion energy. The cross-correlation functions are obtained from ambient noise to acquire accurate phase velocity of surface waves. The dispersion curves of surface waves are inverted for shear (S)-wave velocity profiles. The faults revealed in the inversion profiles match well with the previous geological references. The inverted S-wave velocity profiles are consistent with the results of controlled source audio-magnetotelluric in terms of the characteristics of the layered structures. Our synthetic and real-world tests demonstrated that the waveforms of virtual shot gathers and dispersion images of surface waves are affected by interior sources of a receiver array. Results indicated that the survey arrays should be distributed along roads instead of crossing them. The success of this case study showed that MAPS has the great potential for fault investigation using ambient noise in town environment.

Active and passive seismic surface wave methods for levee assessment in the Sacramento–San Joaquin Delta, California, USA

ABSTRACTSeismic surveys were performed using a novel application of combined active and passive surface wave methods to evaluate the integrity of levees protecting islands in the Sacramento–San Joaquin Delta, California, USA, from flooding. Delta islands have been undergoing rapid subsidence during the past century due to farming practices that have led to the loss of a surficial peat layer. A large earthquake on any one of several active faults in the region could cause multiple levee failures and extensive flooding in the Delta. Surface wave surveys were carried out along the crest of levees using the active method (2D multichannel analysis of surface waves) and along the base of levees using the passive method (microtremor array method). This allowed 2D seismic S‐wave velocity (VS) profiles to be prepared for each site by combining shallow data from the active survey along the crown of the levee with deeper data from a passive survey along the toe of the levee. TheseVS profiles reveal a low‐velocity peat layer beneath the levee body that was confirmed by geotechnical borehole logs. Lateral variability of the levee was evaluated using average velocity to the base of the levee versus along‐levee distance.

Surface-wave survey at a ground cave-in site in Abira town, Hokkaido

Surface-wave survey at a ground cave-in site in Abira town, Hokkaido

Multichannel analysis of surface waves (MASW) for offshore geotechnical investigations

Multichannel analysis of surface wave (MASW) surveys are commonly used onshore to produce shear wave velocity (Vs) profiles. This paper describes its use in offshore geotechnical investigations (underwater MASW - UMASW) where the focus was on the upper 15 m of the sediment profile to aid the design of structures such as marine pipelines, cable routes and shallow anchor systems. UMASW was shown to provide reliable data in Irish offshore conditions in water depths of up to 50 m. The receiver spacing and array length, rather than the characteristics of the air gun seismic energy source, were the primary control on signal penetration and resolution of individual sediment layers. Good resolution of the properties of the upper 5 m of sediment was found by reducing the receiver spacing to as low as 0.3 m. A test site, with a broad intertidal zone, allowed coincident land, marine and direct measurements to be compared and Vs profiles obtained from UMASW, onshore MASW and by seismic cone testing (SCPTU) were in good agreement. Vs profiles estimated from published correlations with CPTU data in sandy sediments agreed well with the measured values. Inversion of data using different software packages showed only a minor variation in results.

Practical configured microtremor array measurements (MAMs) for the geological investigation of underground space

Underground space utilization is becoming increasingly essential for modern metropolitan cities such as Singapore. Mapping a soil/rock interface using traditional borehole investigation methods is expensive and difficult, owing to the numerous physical constraints within a built-up city. Boreholes are often far apart, resulting in many unforeseen ground conditions during subsequent excavation. Geophysical methods are sometimes employed as possible alternatives for fast, economical, and efficient bedrock surveys. The goal of this study is to investigate the practical details of applying microtremor array measurement (MAM) as a non-invasive surface wave survey for mapping soil/rock interfaces in Singapore. Critical configurations in field data acquisition are examined, and practical recommendations for array construction are provided. In addition, 30 in situ MAM tests are carried out for two major geological formations in Singapore. From the results, a standard shear wave velocity (Vs) of 500 m/s is found to be suitable for interpreting the soil/rock interface, for the Bukit Timah Granite and Jurong formations. However, the method does not predict well when soft Kallang formation deposits are present. Other limitations are also discussed in the later parts of this paper. Conclusions and practical recommendations are discussed, providing constructive guidance to the industry. The proposed Vs-based method and associated guidelines and limitations can be used to create a digital geological database and are especially useful for rock profiling in an urban environment.

Surface wave surveys for imaging ground property changes due to a leaking water pipe

This study demonstrates the use of Multi-channel Analysis of Surface Waves (MASW) to measure changes in Rayleigh wave velocity relating to both the initial trench construction and subsequent simulated failures (water leaks) of a buried water-pipe. The MASW field trials were undertaken in conjunction with a wider suite of geophysical monitoring techniques at a site in South-west England, within an area of clayey sandy SILT. The Rayleigh wave velocity through a soil approximately equals the shear wave velocity, which in turn is predominantly dependant on the shear modulus of the soil (G) and this can be inferred to give a measure of the relative strength of a soil. It is proposed that the time-lapse measurement of Rayleigh wave velocity may be used to monitor ongoing changes in soil strength and therefore the MASW technique could perform a significant role in monitoring the initiation/progression of any internal processes within a geotechnical asset, before they would otherwise be identified through visual inspection alone.

Geotechnical site investigation for tunneling and underground works by advanced passive surface wave survey

This study introduces crosscorrelation seismic interferometry, a new and feasible complimentary surface wave survey for geotechnical site investigation for tunneling and underground works. Crosscorrelation seismic interferometry uses ambient noise as source to estimate the green’s functions received by geophones. The proposed methodology is presented and demonstrated by three case studies in Singapore. The 1st case study demonstrates the workflow of the proposed method. Conventional active multichannel analysis of surface waves (MASW) and passive microtremor array measurement (MAM) have also been carried out on the same site. The comparison with classic active MASW shows that the dispersion curves and shear wave velocity profiles derived by crosscorrelation are more comparable and reasonable. With multiple signal classification (MUSIC) beamforming, the direction of arrival (DOA) of ambient noise field can be characterized. As the prerequisite of crosscorrelation method, with the known DOA, it also affords the opportunity to measure both Rayleigh and Love waves. The 2nd case study demonstrates that the polarization of shear wave velocities can be distinguished by the proposed method. The 3rd case study shows a feasible way to construct a 2D shear wave velocity profile. In short, with a simple linear array, fewer geophones, crosscorrelation is considered to be an attractive complement to the conventional MAM and MASW survey.

Seismic site classification and correlation between VS and SPT-N for deep soil sites in Indo-Gangetic Basin

The Indo-Gangetic Basin (IGB) is occupied by the thick deposits of different types of loose to dense soil due to the active sedimentation. Till date, no detailed study has been carried out on seismic site characterization, and classification considering shear wave velocity >50 m depth. In this study, surface wave survey was used for determining the shear wave velocity (VS) variation with depth at 276 locations in the IGB using low-frequency geophones by performing combined active (Multichannel analysis of surface waves, MASW) and passive (Ambient Noise) surveys. To study the spatial variability of VS, based on the sediment deposition and geological variability, the whole IGB has been divided into Punjab-Haryana region (PHR), Uttar Pradesh region (UPR), and Bihar region (BR). Firstly, using the least square, orthogonal, and mixed effect approaches, a new correlation between the VS and SPT-N has been developed for all the three regions separately. The VS and SPT-N correlation has been developed considering both corrected and uncorrected SPT-N value. The residuals have been determined using the observed and the predicted VS values from newly developed VS and SPT-N correlation from each approach. For the same SPT-N value, correlation for UPR region is predicting high VS value as compared to other two regions. Studying the variation of residuals with VS, it is determined that the mixed effect is performing better for VS ≤ 250 m/s and orthogonal for VS > 250 m/s. At higher N-value, difference between VS values for all the three regions are noticeable. Further, the newly developed relationships are compared with the existing VS and SPT-N relationship. Additionally, the IGB is classified based on the average shear wave velocity in the top 30 m (VS30) as per the National Earthquake Hazards Reduction Program (NEHRP) and compared with Eurocode 8 (EC8). The VS30 is high in the southern part of the BR and UPR and low near to the active channel deposition and major part of the IGB is classified as seismic site class D. Most of the IGB sites have experienced severe damage either due to local site effects or liquefaction during past earthquakes. Therefore, the spatial variability of the average shear wave velocity at different depths, i.e., at top 5,10,15,20, 30 50, 100, 150, 200, 250 and 300 m are also estimated and compared with the available basement depth map.

Halden research site: geotechnical characterization of a post glacial silt

This paper describes the geology and geotechnical engineering properties of the Halden silt; a 10–12 m thick deposit of fjord-marine, low plasticity clayey silt. Over the last six years, the test site has been well characterized by combining the results from a number of geophysical and in situ tools, including; electrical resistivity tomography, multi-channel analysis of surface wave surveys, cone penetration testing, dissipation testing, in situ pore pressure measurements, seismic flat dilatometer testing, field vane testing, self-boring pressure meter testing, screw plate load testing and hydraulic fracture testing. The results from these investigations assist the interpretation of layering and in situ soil properties. Soil sampling and advanced laboratory testing have provided data for interpretation of geological setting and depositional history, soil fabric, strength, stiffness and hydraulic properties. However, interpretation of the stress history, based on oedometer tests and clay-based correlations to the cone penetration test, are unreliable. They contradict the depositional history, which suggests that the soil units at the site are near normally consolidated, except for some surface weathering and desiccation. Further, undrained shear strength interpretations are complex as the in situ tests are potentially influenced by partial drainage, and conventional undrained triaxial tests do not provide a unique (peak) undrained shear strength. Despite certain interpretation challenges the paper presents important reference data to assist in the interpretation and assessment of similar silts, and provide some guidance on important geotechnical properties for projects where limited design parameters are available.

Surface-Wave Extraction Based on Morphological Diversity of Seismic Events

It is essential to extract high-fidelity surface waves in surface-wave surveys. Because reflections usually interfere with surface waves on X components in multicomponent seismic exploration, it is difficult to extract dispersion curves of surface waves. To make matters worse, the frequencies and velocities of higher-mode surface waves are close to those of PS-waves. A method for surface-wave extraction is proposed based on the morphological differences between surface waves and reflections. Frequency-domain high-resolution linear Radon transform (LRT) and time-domain high-resolution hyperbolic Radon transform (HRT) are used to represent surface waves and reflections, respectively. Then, a sparse representation problem based on morphological component analysis (MCA) is built and optimally solved to obtain high-fidelity surface waves. An advantage of our method is its ability to extract surface waves when their frequencies and velocities are close to those of reflections. Furthermore, the results of synthetic and field examples confirm that the proposed method can attenuate the distortion of surface-wave dispersive energy caused by reflections, which contributes to extraction of accurate dispersion curves.

Imposing Active Sources during High-Frequency Passive Surface-Wave Measurement

Abstract Passive surface-wave utilization has been intensively studied as a means of compensating for the shortage of low-frequency information in active surface-wave measurement. In general, passive surface-wave methods cannot provide phase velocities up to several tens of hertz; thus, active surface-wave methods are often required in order to increase the frequency range. To reduce the amount of field work, we propose a strategy for a high-frequency passive surface-wave survey that imposes active sources during continuous passive surface-wave observation; we call our strategy “mixed-source surface-wave (MSW) measurement.” Short-duration (within 10 min) passive surface waves and mixed-source surface waves were recorded at three sites with different noise levels: namely, inside a school, along a road, and along a railway. Spectral analysis indicates that the high-frequency energy is improved by imposing active sources during continuous passive surface-wave observation. The spatial autocorrelation (SPAC) method and the multichannel analysis of passive surface waves (MAPS) method based on cross-correlations were performed on the recorded time sequences. The results demonstrate the flexibility and applicability of the proposed method for high-frequency phase velocity analysis. We suggest that it will be constructive to perform MSW measurement in a seismic investigation, rather than exclusively performing either active surface-wave measurement or passive surface-wave measurement.