High-resolution Seismic Reflection Method Research Articles

Application of Complex Geophysical Methods for the Detection of Unconsolidated Zones in Flood Dikes

The flood levees in the vicinity of Krakow city (Poland) are, in some places, over 100 years old. Thereupon, in the flood dike, and its subsoil, can appear unconsolidated zones, which, during the flood stage, can be a simple way of water flow and/or even can be the place where the levee body will be destroyed. This phenomenon took place in Wawrzeńczyce village, near Krakow city, during the flood in 2010. The geophysical research was carried out, in order to develop a methodology of recognition of potential areas where the levee body can be damaged. The geophysical surveys were conducted with the use of electrical and electromagnetic methods, as well as utilizing the seismic method. The general identification of examined media was realized by the electrical resistivity tomography (ERT) method. The ERT surveys were supplemented by capacitively-coupled resistivity (CCR) measurements, in order to analyze the usefulness of the CCR method for the examination of river dikes and reduction of interpretation ambiguity. The ground penetrating radar (GPR) method detected small anomalies in the body dike, due to the very high resolution of this method, which were not detected by the ERT and CCR techniques. During GPR surveys, non-standard measurement techniques were applied. Finally, the high-resolution seismic reflection (HRSR) method provided a clear and high-resolution image of the dike structure up to the water table and assisted with the identification of the hazard non-consolidated zones.

Application of Combined Geophysical Methods for the Examination of a Water Dam Subsoil

The paper presents the results of geophysical measurements that were carried out in the vicinity of the water dam/water reservoir supplying the city of Bielsko-Biala with drinking water. The measurements were performed in order to non-invasively detect faults, fractured zones and areas filled with breccia, which may be, at the same time, a preferential path of groundwater flow. The aforementioned factors influence the stability of the dam. The general identification of the examined media was realized by the electrical resistivity tomography method. The ERT surveys were supplemented by capacitively-coupled resistivity. The electrical methods allowed them to recognize geological settings, indicate possible fault locations, and point out the fault plane as a path of water flow. The ground penetrating radar method detected fractured and filled water areas and underground water paths in the dam’s forefield as a result of the method’s very high resolution. The high resolution seismic reflection method provided a clear and high resolution image of the relatively deep geological structure and verified a location and the run of the faults. In general, the complex geophysical-geological interpretation enabled classification of the unconsolidated/fractured zones associated with faults as a place where the erosion process is the most intense and can bring danger on the dam. Finally, it was confirmed that the area should be the subject of geophysical monitoring.

Investigation of Active Tectonics of Edremit Gulf, Western Anatolia (Turkey), Using High-Resolution Multi-Channel Marine Seismic Data

The Edremit Gulf is situated on the upper Miocene transtensional basin in the Western Anatolia and formed by the interaction between the North Anatolian Fault (NAF) and the N-S extensional tectonic regime of the Aegean domain. Our study is aimed to investigate the structural effects of these tectonic forces in the Gulf. Thus, approximately 300km. seismic data were collected within the Gulf area using the high-resolution seismic reflection method. The results indicated that the interpretation of the data, an E-W oriented, strike-slip fault system (Edremit Bay Fault - EBF) was identified in the Gulf as a possible continuation of the Havran - Balıkesir Fault Zone which can be followed on land. Likewise, a second strike-slip fault system (Edremit - Lesbos Fault; ELF) was observed which crosses the Gulf towards Lesbos Island in the NE-SW direction. This system was interpreted as the possible continuation of the Yenice - Gönen Fault Zone which is thought to be the branch of the North Anatolian Fault.

Interlobate esker aquifer characterization by high resolution seismic reflection method with landstreamer in SW Finland

The Virttaankangas interlobate esker with 100 m thick sediments has a complex depositional history. It is one of the largest groundwater reserves in Finland and hosts a managed artificial recharge plant providing potable water for the 300,000 inhabitants of the Turku region. We researched the characteristics of the esker aquifer both on a major fracture valley and on an esker ridge with a low groundwater table. This study presents the results of the first landstreamer-based high-resolution seismic reflection survey in Finland conducted in 2011. The esker core (main aquifer) position was delineated accurately throughout the entire area with continuous seismic data compared to a previous sedimentological model, gravimetric data and reference drillings. New features related to the widening of the coarse-grained unit of the esker core as well as a previously unknown daughter esker adjacent to the main esker core were revealed. These new findings are in agreement with the existing 3-D hydrogeological model. Our research provides valuable data on the high-resolution seismic reflection surveying of thick interlobate glaciofluvial deposits on two areas with differing bedrock topography on crystalline basement rocks.

High-Resolution Seismic Reflection Investigation of Subsidence and Sinkholes at an Abandoned Coal Mine Site in South Africa

The high-resolution seismic reflection method was conducted at an abandoned coal mine site located in the Benoni area, near the city of Johannesburg, South Africa, with the aim of investigating the subsidence- and sinkhole-related features that are commonly observed in the area. Like many old abandoned coal mine sites, the study area lacks adequate mine records that show the extent of the underground coal mining activities that took place in the area in the late 1930s. The preliminary geotechnical investigation conducted in the study area using percussion drilling had also confirmed the existence of underlying weathered dolomitic rocks that may give rise to dolomite-related sinkholes and subsidence. The seismic survey has revealed the occurrence of subsidence and sinkhole features in the area to be due to the collapse of the colliery roof into subsurface voids caused by coal extraction that took place at the depth between 7 and 13 m, as well as the dissolution cavities that exist within the underlying dolomite formation at the depth of about 50 m below the surface. The size of the coal-mining-related voids varies between 10 and 15 m and corresponds to the size of the room and pillar mining technique employed in the coal extraction, while the size of the dissolution cavities that exist within the underlying dolomite formation varies from 2 to 10 m.

Performing high resolution seismic reflection for mapping Bauxite layers

The seismic method is able to produce highly accurate images of the Earth's subsurface. Having such detail is not only an important factor in mining, but also in civil engineering. Bauxite exploration attracts both government and industrialists to invest in it because of the high percentage of aluminum present. The economic importance of extracting aluminum from bauxite encouraged us to take this challenge; to image bauxite layers by using a high-resolution seismic reflection method at Al Qassim, Saudi Arabia. Since the subsurface structure of the area is complex, this high-resolution reflection method was carried out along a 2D line with geophone and source interval, with settings at 5 m. The result for the seismic section shows that the depth and thickness of the bauxite layer varied from 20 to 34 m, and 3 to 7 m respectively. In addition, the bauxite layer was sandwiched between clay layers. In order to achieve an even more precise depth than presented by seismic section alone, we tied the drilled wells to the seismic data and we accomplished a well match with an approximation error of 1 - 2 m, which may have been caused by the upper clay layer or by very shallow loose subsurface material. The seismic method thus applied shows the ability to detect significant details within the near surface of the earth, and considers more cost-effective than only drilled wells.

Geophysical Model of Coal Prospecting in Uplift Area

The forecast and verification of concealed coal field in China mainly focus on the concealed uplift area (or exposure area of bedrock) and the slope of the known coal field and its surrounding area of sinking area. However, the coal inside the concealed uplift area where it is believed to be no coal is rarely studied. Based on regional geological setting and comprehensive study, the low gravity and low magnetic area is considered as target area for relict concealed coal field. Then high-resolution seismic reflection method is used to ascertain the thickness of Cenozoic rock strata and the depth of coal bed in the target area directly. Through the drilling verification, the result is quite good. In conclusion, gravity, magnetic together with seismic method is an effective way for prospecting concealed coal field in the uplift area.

Imaging bauxite layers using the high-resolution seismic reflection method

The seismic method is able to produce highly accurate images of the Earth’s subsurface. Having such detail is not only an important factor in mining, but also in civil engineering. Bauxite exploration attracts both government and industrialists to invest in it because of the high percentage of aluminum present. The economic importance of extracting aluminum from bauxite encouraged us to take this challenge; to image bauxite layers by using a high-resolution seismic reflection method at Al Qassim, Saudi Arabia. Since the subsurface structure of the area is complex, this high-resolution reflection method was carried out along a 2D line with geophone and source interval, with settings at 5 m. The result for the seismic section shows that the depth and thickness of the bauxite layer varied between 20 to 34 m, and 3 to 7 m respectively. In addition, the bauxite layer was sandwiched between clay layers. In order to achieve an even more precise depth than presented by seismic section alone, we tied the drilled wells to the seismic data and we accomplished a well match with an approximation error of 1-2 m, which may have been caused by the upper clay layer or by very shallow loose subsurface material. The seismic method thus applied shows the ability to detect significant details within the near surface of the earth, and is considered more cost- effective than only drilled wells.

Shallow subsurface imaging using high resolution seismic reflection methods

In order to evaluate the use of shallow seismic technique to map the bedrock up to the depth of 20-25 meters, three high resolution seismic reflection profiles were carried out. The data were acquired using a Strata Visor with 48-channel, 40 Hz geophones and a weight drop system as seismic source. Seismic reflection data were recorded using a CMP (common mid-point) acquisition method. The results show that the bedrock lies at about 18-25 meters depth. The bedrock related horizon observed here is of low frequency, its depth is almost similar in all three seismic lines and thus giving us the enough confidence in results and also following the subsurface structure. Reflection line 3 is been crossed by reflection line 1 and reflection line 2. To confirm the structure and same statics, I did tie these lines to confirm and the reflectors are exactly matching, hence no need to give any shifting. There is high frequency loss due to high attenuation in near surface. A good structural image of subsurface is visible from the seismic sections and for interpreter it's easy to mark structure and integrate it with other methods. With the proper equipment, field parameters and particularly great care in data collection and processing, we can image reflections from layers as shallow as 25 meters.

High Resolution Seismic Reflection Methods to Detect Near Surface Tuff-Cavities: A Case Study in the Neapolitan Area, Italy

High Resolution Seismic Reflection Methods to Detect Near Surface Tuff-Cavities: A Case Study in the Neapolitan Area, Italy

Performing High Resolution Seismic Reflection for Mapping Bauxite Layers

The seismic method is able to produce highly accurate images of the Earth's subsurface. Having such detail is not only an important factor in mining, but also in civil engineering. Bauxite exploration attracts both government and industrialists to invest in it because of the high percentage of aluminum present. The economic importance of extracting aluminum from bauxite encouraged us to take this challenge; to image bauxite layers by using a high-resolution seismic reflection method at Al Qassim, Saudi Arabia. Since the subsurface structure of the area is complex, this high-resolution reflection method was carried out along a 2D line with geophone and source interval, with settings at 5 m. The result for the seismic section shows that the depth and thickness of the bauxite layer varied from 20 to 34 m, and 3 to 7 m respectively. In addition, the bauxite layer was sandwiched between clay layers. In order to achieve an even more precise depth than presented by seismic section alone, we tied the drilled wells to the seismic data and we accomplished a well match with an approximation error of 1 - 2 m, which may have been caused by the upper clay layer or by very shallow loose subsurface material. The seismic method thus applied shows the ability to detect significant details within the near surface of the earth, and considers more cost-effective than only drilled wells.

Investigation of the weathering layer using seismic refraction and high-resolution seismic reflection methods, NE of Riyadh city

Five seismic refraction and five high-resolution seismic reflection (HRSR) profiles were carried out in northeastern part of Riyadh city to investigate depth of the weathering layer. Results obtained from seismic refraction survey reveal the depths of weathering layer at 12, 25, 17, 12, and 16 m, respectively. On the other hand, HRSR stack sections illustrate the depths of weathering layer at 14, 28, 20, 13, and 18 m, respectively. The weathering layer is composed of alluvial sediments and gravel, which is underlain by a sequence of limestone and dolomite layer. Seismic results from site no. 2 have been found to be in good agreement with lithological information reported from the adjacent water well. The HRSR data generally reveal better signal-to-noise ratio and enhanced resolution compared to the refraction data. Although, the HRSR data failed in achieving high-quality common midpoint (CMP) stacking profile at site no. 3, it provide an improved image of the subsurface features than the refraction data, recognizing it as a potential seismic technique.

Multicomponent high-resolution seismic reflection profiling

Multicomponent seismic reflection methods are a new tool for oil and gas exploration and reservoir monitoring (Miles 1988), but such technologies have not yet been extensively exploited for near-surface exploration related to hydrogeological and/or geotechnical investigations. With the advantage of relatively inexpensive recording systems for near-surface applications, we show that the use of multicomponent high-resolution seismic reflection methods has great potential as a new means of observing and characterizing the physical parameters of the shallow subsurface, and in particular of groundwater reservoirs.

ShallowP- andS-Wave Velocities and Site Resonances in the St. Louis Region, Missouri-Illinois

As part of the seismic hazard–mapping efforts in the St. Louis metropolitan area we determined the compressional and shear-wave velocities (Vp and Vs) to about a 40-m depth at 17 locations in this area. The Vs measurements were made using high-resolution seismic refraction and reflection methods. We find a clear difference in the Vs profiles between sites located on the river floodplains and those located in the upland urban areas of St. Louis. Vs30 (average Vs to 30-m depth) values in floodplain areas range from 200 to 290 m/s (NEHRP category D) and contrast with sites on the upland areas of St. Louis, which have Vs30 values ranging from 410 to 785 m/s (NEHRP categories C and B). The lower Vs30 values and earthquake recordings in the floodplains suggest a greater potential for stronger and more prolonged ground shaking in an earthquake. Spectral analysis of a M3.6 earthquake recorded on the St. Louis–area ANSS seismograph network indicates stronger shaking and potentially damaging S-wave resonant frequencies at NEHRP category D sites compared to ground motions at a rock site located on the Saint Louis University campus.

Geophysical methods applied to fault characterization and earthquake potential assessment in the Lower Tagus Valley, Portugal

The study region is located in the Lower Tagus Valley, central Portugal, and includes a large portion of the densely populated area of Lisbon. It is characterized by a moderate seismicity with a diffuse pattern, with historical earthquakes causing many casualties, serious damage and economic losses. Occurrence of earthquakes in the area indicates the presence of seismogenic structures at depth that are deficiently known due to a thick Cenozoic sedimentary cover. The hidden character of many of the faults in the Lower Tagus Valley requires the use of indirect methodologies for their study. This paper focuses on the application of high-resolution seismic reflection method for the detection of near-surface faulting on two major tectonic structures that are hidden under the recent alluvial cover of the Tagus Valley, and that have been recognized on deep oil-industry seismic reflection profiles and/or inferred from the surface geology. These are a WNW–ESE-trending fault zone located within the Lower Tagus Cenozoic basin, across the Tagus River estuary (Porto Alto fault), and a NNE–SSW-trending reverse fault zone that borders the Cenozoic Basin at the W (Vila Franca de Xira–Lisbon fault). Vertical electrical soundings were also acquired over the seismic profiles and the refraction interpretation of the reflection data was carried out. According to the interpretation of the collected data, a complex fault pattern disrupts the near surface (first 400 m) at Porto Alto, affecting the Upper Neogene and (at least for one fault) the Quaternary, with a normal offset component. The consistency with the previous oil-industry profiles interpretation supports the location and geometry of this fault zone. Concerning the second structure, two major faults were detected north of Vila Franca de Xira, supporting the extension of the Vila Franca de Xira–Lisbon fault zone northwards. One of these faults presents a reverse geometry apparently displacing Holocene alluvium. Vertical offsets of the Holocene sediments detected in the studied geophysical data of Porto Alto and Vila Franca de Xira–Lisbon faults imply minimum slip rates of 0.15–0.30 mm/year, three times larger than previously inferred for active faults in the Lower Tagus Valley and maximum estimates of average return periods of 2000–5000 years for M 6.5–7 co-seismic ruptures.

Three Springs Talc Mine: A new view on an old deposit

A successful application of the high resolution seismic reflection method for talc exploration, is demonstrated using an experimental seismic line, recorded over the Three Springs talc deposit. Since 1973, a variety of ground and airborne geophysical techniques had been applied to talc exploration at Three Springs, with limited success. However, wireline logging and laboratory petrophysical measurements have provided new insights into the physical properties of talc and contrasts between talc and adjacent dolomite and dolerite rocks. In particular, P-wave velocity measurements demonstrated that the elastic contrast between the talc mineralisation and surrounding rocks may be sufficient for the application of seismic reflection methods to talc exploration. Between 1989 and 1993, seismic reflection and refraction surveys were acquired on a single profile across the Three Springs talc deposit. The results of this work were disappointing, apparently contradicting physical property measurements. Greatly improved results from re-processing of the `old? seismic data, in 2000, suggested seismic reflection may indeed assist in mapping of the talc mineralisation, as well as providing important detailed structural information. Additional experimental data acquisition, undertaken in 2000, confirmed the potential application of the seismic reflection method to deposit ? scale talc exploration. However, whether the seismic technique can be routinely applied, in a cost ? effective manner, providing the required geological detail, remains to be seen.

Surface Seismic Refraction/Reflection Measurement Determinations of Potential Site Resonances and the Areal Uniformity of NEHRP Site Class D in Memphis, Tennessee

We determined S-wave velocities (Vs) to about 40-m depth at 65 locations in the Memphis-Shelby County, Tennessee, area. The Vsmeasurements were made using high-resolution seismic refraction and reflection methods on the ground surface. We find a clear difference in the Vsprofiles between sites located on the Mississippi River flood plain and those located to the east, mostly covered by loess, in the urban areas of Memphis. The average Vsto 30-m depth at 19 sites on the modern Mississippi River floodplain averages 197 m/s (±15 m/s) and places 17 of these sites at the low end of NEHRP soil profile category type D (average Vs180-360 m/s). The two remaining sites are type E. Vsto 30-m depth at 46 sites in the urban areas east of the modern floodplain are more variable and generally higher than the floodplain sites, averaging about 262 m/s (±45 m/s), still within category D. We often observed the base of the loess as a prominent S-wave reflection and as an increase in Vsto about 500 m/s. Based on the two-way travel time of this reflection, during an earthquake the impedance boundary at the loess base may generate resonances in the 3- to 6-Hz range over many areas of Memphis. Amplitude spectra from four local earthquakes recorded at one site located on loess indicate consistent resonance peaks in the 4.5- to 6.5-Hz range.

Seismic reflection surveys of the Krško basin structure: implications for earthquake hazard at the Krško nuclear power plant, southeast Slovenia

To improve the geologic model and test the approach, high-resolution seismic reflection methods were used in a re-evaluation study of earthquake hazard assessment at the Krško nuclear power plant (NPP) site. In a 13-km long profile recorded across the eastern part of the Krško basin (20-km long and 10-km wide), which is filled with up to 2 km of Neogene to Quaternary molasse sediments, the most prominent reflection was obtained from the top of the Badenian limestone, whereas the Mesozoic basement was less reflective. A syncline–anticline was interpreted that indicates a compressional tectonic style contrary to the prevailing hypothesis of a graben structure with normal border faults. In addition, very high-resolution shallow reflection profiling was performed at two locations close to the NPP for the detection of near-surface faults. Portable engineering seismic equipment was used for data acquisition to reduce costs and enable measurements in areas with difficult access. Geophone arrays were necessary for the suppression of strong ground roll and guided waves generated in the thick layer of dry gravel. Serious spatial aliasing of ground-coupled air-waves precludes f-k filtering, necessitating the application of an internal mute. Two new subvertical normal faults with displacements of 50 and 80 m at the middle/upper Miocene interface were interpreted in the central part of the basin, while other faults, suggested by surface geological observations, were not confirmed. The further north of the two faults was traced in Pliocene–Quaternary deposits to a depth of 250 m. Reinterpretation of old analogue oil-exploration seismic profiles and gravity modelling has allowed the extension of results to a wider area. In the very high-resolution profile, recorded 0.5-km east of the NPP site, some discontinuities in reflections were established that were interpreted as faults. The possible vertical displacement at the sand (Pl, Q)/marl (Pl) interface is 7 m. The new structural-tectonic data obtained in the vicinity of the NPP requires essential changes to the model for earthquake hazard assessment.

Seismic-Reflection Identification of Susquehanna River Paleochannels on the Mid-Atlantic Coastal Plain

Land-based, high-resolution seismic-reflection methods were used to image Quaternary paleochannels of the Susquehanna River system. Using a portable, 12-channel signal-enhancing seismograph, 12 accelerometers as receivers, and a 4.54-kg sledge hammer struck against an aluminum plate as a source, a sixfold, multichannel seismic profile 2.5 km long was acquired at Taylors Island, Maryland. On the processed seismic profile, pronounced high-amplitude seismic reflections delineate the unconformity between Quaternary and underlying Tertiary sediments and the disconformable contact separating Miocene and Eocene deposits. Subsurface-seismic stratigraphic relationships that clearly indicate the presence of two paleochannels were observed, one believed to be the Exmore paleochannel, projected to underlie northern Taylors Island based on marine seismic data. An overlapping sequence of fill sediments was observed on the eastern margin of the Exmore paleochannel. The second paleochannel may be a tributary of the Exmore or possibly the western edge of the younger Eastville paleochannel. Results from this study indicate that land-based, shallow, high-resolution seismic-reflection data can be used to delineate subsurface geomorphology successfully in coastal plain environments. This technique of defining erosional surfaces and depositional units beneath present land areas, when integrated with chronostratigraphic data, is a powerful tool for developing a better understanding of the Quaternary record.

Premine study of shallow coal seams using high-resolution seismic reflection methods : Henson, H; Sexton, J L GeophysicsV56, N9, Sept 1991, P1494–1503

Premine study of shallow coal seams using high-resolution seismic reflection methods : Henson, H; Sexton, J L GeophysicsV56, N9, Sept 1991, P1494–1503