Shallow Seismic Refraction Survey Research Articles

Application of geophysical techniques for shallow groundwater investigation using 1D-lateral constrained and 2D inversions in Ras Gara area, southwestern Sinai, Egypt

There is an urgent need for greater water resources to support sustainable development in Ras Gara area of southwestern Sinai. Determining the water-bearing zones of the shallow Quaternary aquifer of the Araba Formation in the study region is therefore the main objective of the research. This will be done by using a variety of geophysical techniques, such as DC resistivity sounding and shallow seismic refraction surveys. Using the Schlumberger array (max. AB = 1200 m), the DC data were gathered at 27 VES locations along five primary profiles. At the same locations, 27 spreads totaling 115 m in length of seismic data were also performed. One-dimensional laterally constrained (1D-LCI) inversion is only applied to the DC data in order to generate a best-fit model, whereas 2D inversion is applied to other datasets. The area is divided up into five geo-electrical layers based on the results of 1D-LCI inversion of DC data, and the aquifer is classified into fresh (third layer) and saline bearing-zones (fourth layer). The resistivity values of the fresh-zone range from 8.7 to 26.7 Ω.m, with only low values (5–7.5 Ω.m) found at some VES sites, while the resistivity values of the saline-zone range between 0.9 and 3 Ω.m, except for (14.4 Ω.m) at VES-04. At depths of (2.4–15.6 m) and (8.7–28.5 m) for the fresh and saline zones, respectively. In this region, the shallow low resistive (about 10–100 Ω.m) and intermediate high conductive (< 10 Ω.m) layers of the 2D-DC inverted model represent the fresh and saline zones of the aquifer, respectively. The basement rocks were represented by a deep, extremely high resistive layer that can reach 40,000 Ω.m. Three subsurface layers are identified from the results of the 2D inversion of seismic data (VP1 = 400–1100 m.s−1, VP2 = 1200–1900 m.s−1 and VP3 = 2400–5400 m.s−1). The saturated zone of this aquifer is represented by the second layer (depth, 3.7–20.5 m). The basement rocks are also reflected in the last layer of high velocity. The inversion results and the previously available hydro-geological map data show a good degree of concordance. In the eastern portion of the study area, additional water wells could be drilled for additional water resources.

Geophysical anatomy of counter-slope scarps in sedimentary flysch rocks (Outer Western Carpathians)

A multidisciplinary geophysical survey, consisting of electrical resistivity tomography (ERT), ground penetrating radar (GPR), shallow seismic refraction (SSR) and gravity survey (GS), was used to investigate the counter-slope scarps, one of the typical manifestations of the relaxed zones of rock massifs, and the possible initial stages of deep-seated landslides (DSLs). Two upper parts of the extensive DSLs within the Moravskoslezské Beskydy Mountains (Outer Western Carpathians – OWC) built by the sedimentary flysch rock were chosen as the testing sites. A combined geophysical survey on the flysch rocks was performed on both localities to enhance our present findings. The survey revealed that the ERT is able to reliably detect underground discontinuities, which are manifested at the ground surface by one of the typical landforms (tension cracks, trenches, pseudokarst sinkholes, double-crested ridges and counter-slope scarps). Previous studies suggested that bedrock discontinuities should be depicted by high-resistivity features within ERT surveying. According to SSR and GS, expected zones of weakened rock massif were not confirmed directly underneath the superficial landforms, but they were shifted. Based on the SSR and GS measurements, the depicted high-contrast transitions between high- and low-resistivity domains within the ERT profiles were newly identified as possible manifestation of bedrock discontinuities. The results of GPR measurements give only limited information on the sedimentary flysch rocks, due to shallow penetrating depth and locally strong signal attenuation. The combined results of multidisciplinary geophysical surveying confirmed an importance of employing more than one geophysical technique for integrated interpretations of measured data. Integrated interpretations of the measured geophysical data provided a new insight into massif disintegration and the geomorphic origin of the landforms related to the DSL.

Terrane Boundary Geophysical Signatures in Northwest Panay, Philippines: Results from Gravity, Seismic Refraction and Electrical Resistivity Investigations

Northwest Panay consists of two terranes that form part of the Central Philippine collision zone: Buruanga Peninsula and Antique Range. The Buruanga Peninsula consists of a Jurassic chert-clastic-limestone sequence, typical of oceanic plate stratigraphy of the Palawan Micro-continental Block. The Antique Range is characterized by Antique Ophiolite Complex peridotites and Miocene volcanic and clastic rocks, representing obducted oceanic crust that serves as the oceanic leading edge of the collision with the Philippine Mobile Belt. The Nabas Fault is identified as the boundary between the two terranes. This study employed the gravity method to characterize the Northwest Panay subsurface structure. Results indicate higher Bouguer anomaly values for Buruanga Peninsula than those for Antique Range, separated by a sudden decrease in gravity values toward the east-southeast (ESE) direction. Forward gravity data modeling indicates the presence of an underlying basaltic subducted slab in the Buruanga Peninsula. Furthermore, the Nabas Fault is characterized as an east-dipping thrust structure formed by Buruanga Peninsula basement leading edge subduction beneath Antique Range. Additional geophysical constraints were provided by shallow seismic refraction and electrical resistivity surveys. Results from both methods delineated the shallow subsurface signature of the Nabas Fault buried beneath alluvium deposits. The gravity, seismic refraction and electrical resistivity methods were consistent in identifying the Nabas Fault as the terrane boundary between the Buruanga Peninsula and the Antique Range. The three geophysical methods helped constrain the subsurface configuration in Northwest Panay.

Tracing of the Avenue of the Ram-Headed Sphinxes Remains Using Geophysical Investigations, Luxor, Egypt

Throughout 3000 years ago, over the New Kingdom in the Pharaonic period, the Ram-headed Sphinxes Avenue connected Karnak and the Temples of Luxor, a processional avenue was lined on both sides by 1200 statues of sphinxes. The lining of the avenue was erased. Centuries over centuries this avenue has been buried with its statues under about 2 m of silt and sand, and urban development covered it with housing, asphaltic streets, and other structures, obscuring its route and interrupting this dramatic connection. This paper focuses on the discovery of some of these Sphinx statuses and remains at a suggested part of the avenue using both near-surface magnetic and shallow seismic refraction methods. A gradiometer survey was conducted in an area that amounted 576 m2 as (48 m × 12 m) to measure the vertical magnetic gradient with a high resolution instrument with 0.25 m sampling interval. A superior detection was accomplished by using the analytic signal and Euler deconvolution techniques. The shallow seismic refraction survey was done in the same area to illustrate the lithology of layers material with 1 m interval; both P and S waves were measured to calculate the geotechnical properties of the area to sustain the sketch of structures’ boundaries. We have lucratively detected six main structures; they can be the pedestal of these Ram-headed Sphinx statues. Mining a small part of the study area has proven the reliability of, both the magnetic and shallow seismic refraction discoveries, and the shallowness and composition of the detected features.

Site-specific shear wave velocity investigation for geotechnical engineering applications using seismic refraction and 2D multi-channel analysis of surface waves

In order to quantify the near-surface seismic properties (P- and S-wave velocities, and the dynamic elastic properties) with respect to the depth at a specific area (6th of October club), we conducted a non-invasive and low cost active seismic survey. The primary wave velocity is determined by conducting a P-wave shallow seismic refraction survey. The dispersive characteristics of Rayleigh type surface waves were utilized for imaging the shallow subsurface layers by estimating the 1D (depth) and 2D (depth and surface location) shear wave velocities. The reliability of the Multi-channel Analysis of Surface Waves (MASW) depends on the accurate determination of phase velocities for horizontally traveling fundamental mode Rayleigh waves. Consequently, the elastic properties are evaluated empirically. The Vs30 (average shear wave velocity down to 30m depth), which is obtained from the MASW technique, plays a critical role in evaluating the site response of the upper 30m depth. The distribution of the obtained values of Vs30 through the studied area demonstrates site classes of C and D, according to the NEHRP (National Earthquake Hazard Reduction Program) and IBC (International Building Code) standards.

Detection of karstic limestone bedrock by shallow seismic refraction in an area west of Assiut, Middle Egypt

The main goal of this study was the detection of complex surface and internal structures of limestone bedrock over the entire area planned for urban development on the lower Eocene plateau, west of Assiut, Egypt. A 2.5D shallow seismic refraction survey provided sufficient resolution for mapping faults and karst at the scale required for civil engineering plans. The 3D P-wave seismic velocity map was developed from integration of a series of 2D spreads recorded along a 2D grid using only inline spreads.

Seismic Constraints on Critical Zone Architecture, Boulder Creek Watershed, Front Range, Colorado

We use a minimally invasive, shallow geophysical technique to image the structure of the critical zone from surface to bedrock (0–20 m) in two small drainages within the Boulder Creek Critical Zone Observatory (BcCZO). Shallow seismic refraction (SSR) surveys provide a three‐dimensional network of two‐dimensional cross‐sections (termed quasi‐3D) of critical zone compressional wave velocity (Vp) structure within each catchment, yielding a spatial description of the current critical zone structure. The two catchments, Betasso and Gordon Gulch, represent contrasting geomorphic histories within the Front Range: Betasso shows hillslope response to a late Cenozoic increase in fluvial incision of Boulder Creek, while Gordon Gulch represents more steady erosion. The mean depth to fresh bedrock in both catchments is roughly 15 m. Unique subsurface features in each catchment reflect active geomorphic processes not suggested by similarities in mean interface depths. Betasso contains thick disaggregated materials high in the drainage that are nearly absent near the outlet. This presumably reflects the impact of base‐level lowering, which we suggest has progressed roughly 500 to 1000 m up into the catchment. Aspect‐driven differences in the subsurface within each catchment add complexity and overprint the broader geomorphic signals. Shallow seismic refraction subsurface structure models will guide future investigations of critical zone processes from landscape to hydrologic modeling and are invaluable as connections between time‐consuming point measurements of physical, chemical, and biological processes.

Influence of crack distribution of rocks on P‐wave velocity anisotropy – a laboratory and field scale study‡

ABSTRACTThe purpose of this paper is the comparison of P‐wave velocity and velocity anisotropy, measured at different scales under laboratory and field conditions. A shallow seismic refraction survey with shot/receiver spacing of up to 10 m was carried out on a flat outcrop of lhertzolite in the southern part of the Balmuccia massif. Oriented rock samples were also obtained from the locality. The particular advantage of the laboratory method used is the possibility of measuring velocity in any direction under controlled conditions. Laboratory tests were made on spherical peridotite samples, 50 mm in diameter, by ultrasonic velocity measurements in 132 directions (meridian and parallel networks) under confining stress ranging from atmospheric to 400 MPa. The mean P‐wave velocity of the field and laboratory data differed by between 20–30%. In addition, P‐wave velocity anisotropy of 25% was detected in the field data. Whereas the anisotropy in the laboratory samples in the same orientation as the field surveys was less than 2%. This observed scaling factor is related to the different sampling sizes and the difference in frequencies of applied elastic waves. With an ultrasonic wavelength of 10 mm, laboratory samples represent a continuum. The field velocities and velocity anisotropy reflect the presence of cracks, which the laboratory rock samples do not contain. Three sub‐vertical fracture sets with differing strikes were observed in the field outcrop. Estimates of fracture stiffness from the velocity anisotropy data are consistent with other published values. These results highlight the difficulty of using laboratory velocity estimates to interpret field data.

Estimating the near surface amplification factor to minimize earthquake damage: a case study at West Wadi Hagoul area, Egypt

ABSTRACTThe damage caused by earthquake occurrences in different localities all over the world necessitates the evaluation of the underground and/or sub‐soil structure for strategic projects. The case study is the proposed area for a new factory construction that lies 3 km west of Suez Cement factory, in the area between Kottamiya and Ain Sokhna. The shallow seismic refraction survey was carried out through 10 major lines (grid lines), comprising 30 seismic profiles. The microtremor measurements were done at 25 locations at the grid intersection points. The obtained compressional (P) and horizontal shear (SH) wave velocities, with the horizontal to vertical (H/V) spectral ratios, are used to deduce the subsurface structures, to evaluate the elastic and dynamic properties and the transfer function at both the surface and bedrock. The results illustrate that there is a good correlation between the fundamental frequencies deduced through the theoretical transfer function and the H/V spectral ratio. The maximum value of ground motion amplification factor of the study area is 3.3 at a corresponding frequency of 7.8 Hz.

Waveform inversion of shallow seismic refraction data using hybrid heuristic search method

We propose a waveform inversion method for SH-wave data obtained in a shallow seismic refraction survey, to determine a 2D inhomogeneous S-wave profile of shallow soils. In this method, a 2.5D equation is used to simulate SH-wave propagation in 2D media. The equation is solved with the staggered grid finite-difference approximation to the 4th-order in space and 2nd-order in time, to compute a synthetic wave. The misfit, defined using differences between calculated and observed waveforms, is minimised with a hybrid heuristic search method. We parameterise a 2D subsurface structural model with blocks with different depth boundaries, and S-wave velocities in each block. Numerical experiments were conducted using synthetic SH-wave data with white noise for a model having a blind layer and irregular interfaces. We could reconstruct a structure including a blind layer with reasonable computation time from surface seismic refraction data.

Simulating time-histories and pseudo-spectral accelerations from the 1992 Cairo earthquake at the proposed El-Fayoum New City Site, Egypt

El-Fayoum New City represents one of the new urban settlements that are recently erected all over Egypt. Because seismic recordings are not available, I used the stochastic method to simulate the largest damaging earthquake from the closest seismic source to the proposed area of the city. To verify the method and its computed results in Egypt, a study termed “method verification” was performed. I found that the October 12, 1992, earthquake (Mb = 5.8) that occurred southwest of Cairo in the vicinity of the Dahshour region, at the coordinates 29.77°N, 31.07°E, is a significant earthquake to the city. The parameters of the path from the hypocenter of the event to the city were taken into consideration. To determine the site parameters, a shallow seismic refraction survey was carried out in the studied area. Accordingly, I simulated time-histories and pseudo-spectral accelerations from the October 12, 1992, earthquake at the location of seismic profiles. Finally, it is demonstrated that the site is characterized by high ground motion amplification factors, producing a high ground motion acceleration value.

A 3D 3C Shallow Seismic Refraction Survey Across a Shear Zone at Bungendore

A three dimensional (3D) three component (3C) shallow seismic refraction survey was recorded across an extension of the Lake George fault in the butcher's paddock at Bungendore. The ANSIR equipment employed 348 channels in a static spread set out as 4 lines of 29 stations with 3 component geophones. The seismic energy source was a IVI Minivib, T15000. P- & S-wave sweeps were employed. Shear zones are an important concern in most geotechnical investigations. However, they can be especially difficult to separate from artifacts of inversion algorithms, because the traveltime anomalies are relatively small. Saline groundwater in major bedrock fractures, appears to be the source of dryland salinity in the Dubbo area. In other areas of dryland salinity, eg Wagga, the source is wind blown salt. Identifying the source of the salinisation is important in selecting the correct remediation strategy.

Water Bottom Seismic Refraction Survey for Engineering Applications

ABSTRACT The accurate mapping of the basement is one of the most crucial factors in construction of harbour facilities and bridges in the coastal areas. In shallow waters, the seismic reflection method often fails to image the basement geometry beneath the sediment due to reverberation. We present the result of a shallow marine seismic refraction survey using two ships, 12-channel hydrophone arrays deployed on the bottom and a borehole sparker or percussion powder as sources. Velocity structure could be computed by tomography algorithm since more than 6 different source points had been applied for one spread. The comparison of the results of the refraction survey with drilling logs demonstrates remarkable consistency in basement geometry. It thus appears that the refraction method in this study is an efficient and cost- effective way to investigate the basement structure in coastal area, river, and lake.

Shallow seismic refraction used to map the hydrostratigraphy of Nukuoro Atoll, Micronesia

Results from a shallow seismic-refraction survey on Nukuoro indicate that the distribution of fresh and brackish groundwater on that atoll island is controlled by a three-dimensional mosaic of carbonate facies. Each facies is characterized by a distinct seismic velocity which is dependent on the grain size, composition, and abundance of carbonate cement. The refraction survey further indicates that the upper saturated zone is composed of mostly unconsolidated sediments underlain by highly permeable, well-indurated limestone. The fresh-water lens and associated transition zone of fresh to saline groundwater occur within the upper unconsolidated sediments. Measurements of chloride-ion concentrations in water samples collected from sites across the island indicate an asymmetric fresh-water lens with the thickest part of the lens located near the lagoon shoreline. During the 1983 drought, saline water intruded into the island's central topographical depression where taro is cultivated. The intrusion was caused by tidal pumping (upward movement) of brackish water underlying a reef-flat plate, which forms a confining layer over a significant part of the island.

Seismic refraction surveys for predicting the intensity and depth of weathering and fracturing in granitic masses

Abstract Seismic refraction surveys were employed for shallow investigations (down to 20–30 m depth) and conducted across the top of vertical exposures where the underlying geology could be directly inspected. The suitability of shallow seismic refraction surveys for identifying the intensity and depth of rock weathering and fracturing at the respective locations could thus be correctly assessed. Research completed on granites of Jurassic and Cretaceous age from Korea had previously indicated that these granitic materials could be divided with reasonable accuracy into five weathering groups using visual and simple mechanical techniques. Weathering boundaries determined by seismic refraction methods were found to agree within a 2 m variance with visible differences in weathering in the vertical exposure beneath each test site. The intensity of fracturing could also be predicted by seismic refraction surveys with relatively good accuracy. It was concluded that the field seismic survey method in shallow Korean granitic masses could be considered a very useful and cost-effective technique for assessing the intensity and depth of weathering and fracturing.

Shallow Seismic Refraction Survey of Near‐Surface Ground Water Flow

AbstractA shallow seismic refraction survey was conducted as part of a geologic and hydrologic investigation of an area adjacent to a proposed coal strip mine in southeastern Illinois. Data obtained from the survey were used to estimate the thickness and geometry of litho‐logic units within approximately 40 feet of the surface in unconsolidated material overlying bedrock. Data from a nearby ground water monitoring well and several shallow geologic cores obtained in the survey area indicated the presence of a silt‐clay unit roughly 10 feet beneath the surface. This unit strongly inhibits the vertical movement of ground water, resulting in a perched water table.The refraction survey revealed that the morphology of the top of this silt‐clay layer is dominated by a narrow, sinuous channel criss‐crossing the survey region with an overall downward trend in elevation from the mine site to a small creek roughly 0.25 miles away. Detailed knowledge of the location of this channel was used to identify optimal sites for shallow ground water monitoring stations. The method proved to be a relatively rapid and cost‐efficient means of obtaining detailed information concerning the thickness and geometry of the near‐surface unconsolidated materials.

Reply to the discussion submitted by Robert W. Lankston Concerning the article titled Shallow Seismic Refraction Survey of Near Surface Ground Water Flow by Keith A Sverdrup

Groundwater Monitoring & RemediationVolume 6, Issue 2 p. 46-46 Reply to the discussion submitted by Robert W. Lankston Concerning the article titled Shallow Seismic Refraction Survey of Near Surface Ground Water Flow by Keith A Sverdrup First published: March 1986 https://doi.org/10.1111/j.1745-6592.1986.tb01237.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue2March 1986Pages 46-46 RelatedInformation

Discussion on: Shallow Seismic Refraction Survey of Near‐Surface Ground Water Flow by Keith A. Sverdrup, Ground Water Monitoring Review, v. 6, no. 1, pp. 80‐83, by Robert W. Lankston, University of Arkansas, Department of Geology

Discussion on: Shallow Seismic Refraction Survey of Near‐Surface Ground Water Flow by Keith A. Sverdrup, Ground Water Monitoring Review, v. 6, no. 1, pp. 80‐83, by Robert W. Lankston, University of Arkansas, Department of Geology

THE CORRELATION REFRACTION METHOD AS APPLIED TO WEATHERED ZONE STUDIES IN A GRANITE TERRAIN*

AbstractThe combined observation of first and later arrivals in shallow seismic refraction surveys, particularly on hard rock terrains, is discussed. Details of experimental weathered‐zone investigations by the correlation refraction method in a granite terrain (i.e. field procedure, seismograms obtained, plotting of the data, and identification of the waves are presented). Complete travel time data and interpreted subsurface sections of a few test refraction surveys are included. In one instance the interpreted results of normal and converted refracted wave data have been tested by drilling at three points along a 220 m long profile.

Determination of depths to an irregular interface in shallow seismic refraction surveys using a pocket calculator

Engineering geologic problems commonly involve the determination of depth to bedrock where it is overlain by residual soil or dry and saturated alluvium. The buried bedrock surface is commonly irregular and the nature of such irregularities must be known, for example, in (1) foundation studies where irregularities on the bedrock surface could indicate faults, or (2) groundwater studies where low areas in the bedrock may indicate channels for groundwater flow which may be targets for drilling. Seismic refraction surveys have proven to be a simple and accurate means of providing adequate data for describing irregularities on the bedrock surface, especially when the data are analyzed by the “plus‐minus” method of the wavefront approach. The method can be programmed readily for a Hewlett‐Packard HP-45 hand calculator, enabling rapid reduction of the data in the field. On‐site data reduction and interpretation result in greater efficiency by allowing immediate recognition of those areas where more detailed information may be needed, thereby precluding repeat surveys and reducing costs. For this purpose, suitable computer programs for the two‐ and three‐layer cases are developed, as well as programs for elevation and weathered zone corrections commonly needed in such shallow seismic surveys.