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1
Panjamani, Anbazhagan, Arun Kumar Katukuri, Reddy G.R, Sayed S. R. Moustafa i Nassir S. N. Al-Arifi. "Seismic site classification and amplification of shallow bedrock sites". PLOS ONE 13, nr 12 (26.12.2018): e0208226. http://dx.doi.org/10.1371/journal.pone.0208226.
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Anbazhagan, P., i M. Neaz Sheikh. "Seismic Site Classifications and Site Amplifications for the Urban Centres in the Shallow Overburden Deposits". International Journal of Geotechnical Earthquake Engineering 3, nr 1 (styczeń 2012): 86–108. http://dx.doi.org/10.4018/jgee.2012010105.
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This paper presents seismic site classification practices for urban centres in Australia, China, and India with special emphasis on their suitability for shallow soil sites. The geotechnical aspects of seismic site classifications play a critical role in the development of site response spectra, which is the basis for the seismic design of new structures and seismic assessment of existing structures. Seismic site classifications have used weighted average shear wave velocity of top 30 m soil layers, following the recommendations of National Earthquake Hazards Reduction Program (NEHRP) or International Building Code (IBC) site classification system. The site classification system is based on the studies carried out in the United States where soil layer may extend up to several hundred meters before reaching any distinct soil-bedrock interface. Most of the urban centers in Australia, China, and India are located on distinct bedrocks within few meter depth of soil deposits. For such shallow depth soil sites, NEHRP or IBC site classification system is not suitable. A new site classification based on average soil thickness, shear wave velocity up to engineering bedrock is proposed. The study shows that spectral value and amplification ratio estimated from site response study considering top 30 m soil layers are different from those determined considering soil thickness up to engineering bedrock.
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Parihar, Aditya, i P. Anbazhagan. "Site Response Study and Amplification Factor for Shallow Bedrock Sites". Indian Geotechnical Journal 50, nr 5 (24.01.2020): 726–38. http://dx.doi.org/10.1007/s40098-020-00410-w.
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Aaqib, Muhammad, Duhee Park, Muhammad Bilal Adeel, Youssef M. A. Hashash i Okan Ilhan. "Simulation-based site amplification model for shallow bedrock sites in Korea". Earthquake Spectra 37, nr 3 (15.01.2021): 1900–1930. http://dx.doi.org/10.1177/8755293020981984.
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A new simulation-based site amplification model for shallow sites with thickness less than 30 m in Korea is developed. The site amplification model consists of linear and nonlinear components that are developed from one-dimensional linear and nonlinear site response analyses. A suite of measured shear wave velocity profiles is used to develop corresponding randomized profiles. A VS30 scaled linear amplification model and a model dependent on both VS30 and site period are developed. The proposed linear models compare well with the amplification equations developed for the western United States (WUS) at short periods but show a distinct curved bump between 0.1 and 0.5 s that corresponds to the range of site natural periods of shallow sites. The response at periods longer than 0.5 s is demonstrated to be lower than those of the WUS models. The functional form widely used in both WUS and central and eastern North America (CENA), for the nonlinear component of the site amplification model, is employed in this study. The slope of the proposed nonlinear component with respect to the input motion intensity is demonstrated to be higher than those of both the WUS and CENA models, particularly for soft sites with VS30 < 300 m/s and at periods shorter than 0.2 s. The nonlinear component deviates from the models for generic sites even at low ground motion intensities. The comparisons highlight the uniqueness of the amplification characteristics of shallow sites that a generic site amplification model is unable to capture.
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WANG, C., i J. A. McKEAGUE. "SHORT-RANGE SOIL VARIABILITY AND CLASSIFICATION OF PODZOLIC PEDONS ALONG A TRANSECT IN THE LAURENTIAN HIGHLANDS". Canadian Journal of Soil Science 66, nr 1 (1.02.1986): 21–30. http://dx.doi.org/10.4141/cjss86-002.
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Pedons were described, sampled and classified at 5-m intervals along a 130-m transect in an area typical of the southern Laurentian Highlands in order to assess short-range soil variability. Orthic Ferro-Humic Podzol was the dominant subgroup (25 of 27 sites). Differences in depth to bedrock and in soil water regime resulted in four soil families; bedrock was exposed at one site. At 21 of the 27 sites, however, the pedons were classified in one family: Orthic Ferro-Humic Podzol, coarse loamy, cold, humid. Differences in thicknesses and sequences of horizons resulted in a total of at least nine soil series. At scales of 1:20 000 or somewhat smaller, the soils of map units in the area would be most appropriately indicated as slope phases (10–40% slopes) of families. The dominant family would be the one indicated above with inclusions of shallow to extremely shallow phases and bedrock outcrops. Key words: Soil variability, Podzolic soils, classification of pedons
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Miller, J. J., G. J. Beke, S. Pawluk i H. R. Krouse. "Sulfur and oxygen isotopic composition of sulfates at two saline sites in southern Alberta". Canadian Journal of Soil Science 73, nr 4 (1.11.1993): 633–37. http://dx.doi.org/10.4141/cjss93-061.
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Possible sources of SO4 in soil, drift and bedrock at two saline sites in southern Alberta were investigated using sulfur and oxygen isotope analyses. Slight differences (0.6–5.2 per mil) between δ34S values of SO4 and insoluble S in the geologic material were attributed to kinetic fractionation during oxidation of organic S. Negative δ18O values of SO4 in the shallow (<6 m) bedrock, drift and soil reflected oxidation of reduced S. In contrast, positive δ18O values in the deep (>6 m) bedrock indicated sulfate reduction. The exact source of SO4 could not be determined in this preliminary study. The isotope approach, however, shows promise and warrants more detailed study. Key words: Salinization, sulfates, sulfur isotopes, oxygen isotopes
7
Sims, Richard A., i William D. Towill. "Alternate Strip Clearcutting in Upland Black Spruce: VIII. Shallow-soil Ecosystems and Their Classification". Forestry Chronicle 64, nr 1 (1.02.1988): 70–75. http://dx.doi.org/10.5558/tfc64070-1.
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Shallow-soil sites in the Nipigon-Beardmore area of northern Ontario are widespread and pose unique operational problems for forest managers. Several working definitions of shallow soils are used in Ontario. More accurate regional definitions are required in order that silvicultural decisions for these sometimes fragile sites may be refined or new ones developed. Harvesting and silvicultural options for shallow-soil sites are limited in the North Central Region.A program of Forest Ecosystem Classification (FEC) for the North Central Region has been designed to provide better understanding of shallow sites and a framework of standardized definitions. The FEC describes several shallow-soil types that occur over boulder pavement or bedrock, and differentiates mainly on the basis of depth-to-rock contact, surface organic material thickness and texture of the primary mineral soil particles. Operational application of this classification may require identification of complexes of shallow-soil types.
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Manandhar, Satish, Hyung-Ik Cho i Dong-Soo Kim. "Site Classification System and Site Coefficients for Shallow Bedrock Sites in Korea". Journal of Earthquake Engineering 22, nr 7 (10.05.2017): 1259–84. http://dx.doi.org/10.1080/13632469.2016.1277570.
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Anbazhagan, P., Ketan Bajaj, G. R. Reddy, V. S. Phanikanth i D. N. Yadav. "Quantitative Assessment of Shear Wave Velocity Correlations in the Shallow Bedrock Sites". Indian Geotechnical Journal 46, nr 4 (8.02.2016): 381–97. http://dx.doi.org/10.1007/s40098-016-0181-y.
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Cox, Brady R., i Andrew N. Beekman. "Intramethod Variability in ReMi Dispersion Measurements and Vs Estimates at Shallow Bedrock Sites". Journal of Geotechnical and Geoenvironmental Engineering 137, nr 4 (kwiecień 2011): 354–62. http://dx.doi.org/10.1061/(asce)gt.1943-5606.0000436.
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Lee, Yong-Gook, Sang-Jin Kim, Zeinep Achmet, Oh-Sung Kwon, Duhee Park i Luigi Di Sarno. "Site amplification prediction model of shallow bedrock sites based on machine learning models". Soil Dynamics and Earthquake Engineering 166 (marzec 2023): 107772. http://dx.doi.org/10.1016/j.soildyn.2023.107772.
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Jiménez-Rodríguez, César Dionisio, Mauro Sulis i Stanislaus Schymanski. "Exploring the role of bedrock representation on plant transpiration response during dry periods at four forested sites in Europe". Biogeosciences 19, nr 14 (20.07.2022): 3395–423. http://dx.doi.org/10.5194/bg-19-3395-2022.
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Abstract. Forest transpiration is controlled by the atmospheric water demand, potentially constrained by soil moisture availability, and regulated by plant physiological properties. During summer periods, soil moisture availability at sites with thin soils can be limited, forcing the plants to access moisture stored in the weathered bedrock. Land surface models (LSMs) have considerably evolved in the description of the physical processes related to vegetation water use, but the effects of bedrock position and water uptake from fractured bedrock have not received much attention. In this study, the Community Land Model version 5.0 (CLM 5) is implemented at four forested sites with relatively shallow bedrock and located across an environmental gradient in Europe. Three different bedrock configurations (i.e., default, deeper, and fractured) are applied to evaluate if the omission of water uptake from weathered bedrock could explain some model deficiencies with respect to the simulation of seasonal transpiration patterns. Sap flow measurements are used to benchmark the response of these three bedrock configurations. It was found that the simulated transpiration response of the default model configuration is strongly limited by soil moisture availability at sites with extended dry seasons. Under these climate conditions, the implementation of an alternative (i.e., deeper and fractured) bedrock configuration resulted in a better agreement between modeled and measured transpiration. At the site with a continental climate, the default model configuration accurately reproduced the magnitude and temporal patterns of the measured transpiration. The implementation of the alternative bedrock configurations at this site provided more realistic water potentials in plant tissues but negatively affected the modeled transpiration during the summer period. Finally, all three bedrock configurations did not show differences in terms of water potentials, fluxes, and performances on the more northern and colder site exhibiting a transition between oceanic and continental climate. Model performances at this site are low, with a clear overestimation of transpiration compared to sap flow data. The results of this study call for increased efforts into better representing lithological controls on plant water uptake in LSMs.
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Řezáč, Milan, Vlastimil Růžička, Jan Dolanský i Petr Dolejš. "Vertical distribution of spiders (Araneae) in Central European shallow subterranean habitats". Subterranean Biology 45 (18.01.2023): 1–16. http://dx.doi.org/10.3897/subtbiol.45.95850.
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Shallow subterranean habitats are among the last habitats in Central Europe to be arachnologically researched. Using stratified pipe traps, we studied the vertical distribution of spiders in soil and interspaces in bedrock (shallow subterranean habitats). Specifically, we sampled fauna in different substrates, including limestone, sandy marlstone, sandy marl, claystone, loess, and artificial gravel accumulation. Employing stratified pipe traps allowed us to identify the depth at which particular species occurred. Across multiple years and sampling sites, we collected 76 spider species, 21 of which showed an affinity for subterranean microhabitats. Some of these species occurred in interspaces in soil and bedrock, whereas others have been previously found in subterranean ant nests and animal burrows. We collected five species (Iberina microphthalma, Centromerus cf. piccolo, Porrhomma cambridgei, P. microcavense, and P. microps) almost exclusively at depths over half a meter, suggesting the strong affinity of these species for a subterranean lifestyle. We provide diagrams of these species’ vertical distribution and photo-document eye reduction. Our study demonstrates that poorly studied shallow subterranean habitats harbor diverse subterranean spider fauna, including several previously considered rare species in Central Europe.
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Bergamo, Paolo, Cesare Comina, Sebastiano Foti i Margherita Maraschini. "Seismic characterization of shallow bedrock sites with multimodal Monte Carlo inversion of surface wave data". Soil Dynamics and Earthquake Engineering 31, nr 3 (marzec 2011): 530–34. http://dx.doi.org/10.1016/j.soildyn.2010.10.006.
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Welch, Brian C., i Robert W. Jacobel. "Bedrock topography and wind erosion sites in East Antarctica: observations from the 2002 US-ITASE traverse". Annals of Glaciology 41 (2005): 92–96. http://dx.doi.org/10.3189/172756405781813258.
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AbstractIce stratigraphy from deep-penetrating radar data collected during the 2002 US International Trans-Antarctic Scientific Expedition (US-ITASE) traverse shows evidence of a significant erosion surface and drift-filled basin related to a previously undiscovered 1400m subglacial mountain between Hercules Dome (87˚420 S, 108˚ W) and South Pole. The 3MHz radar profile crosses three subglacial mountains at approximately 458 to the ice-flow direction. Cross-cutting reflectors in the top 500m of ice stratigraphy are interpreted as angular unconformities resulting from wind erosion as the ice deforms over the mountain tops. The unconformities correlate locally with zones of high RADARSAT reflectivity. Several nearby sites with similar relatively high RADARSAT reflectivity adjacent to the traverse indicate that active wind erosion may be taking place at these locations as well. Based on the local correlation between surface wind scour and subglacial topography, we interpret the nearby cluster of bright RADARSAT reflectivity to indicate the presence of a small range of subglacial mountains. The ability to trace isochronal stratigraphy, associated with scour sites using shallow and deep radar, to nearby dated ice cores presents the possibility of exploiting wind-scour zones to access well-dated older ice with shallow-coring equipment.
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Wright, C. "Faulting and overburden and bedrock seismic velocities at Buchans and Gullbridge, Newfoundland, from seismic refraction measurements: applications to shallow geology and exploration". Canadian Journal of Earth Sciences 33, nr 8 (1.08.1996): 1201–12. http://dx.doi.org/10.1139/e96-091.
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P-wave arrival times from seismic reflection surveys recorded at two mine sites in Newfoundland were used to estimate lateral variations in seismic velocity in uppermost bedrock. The abundant information on medium- to long-wavelength lateral variations in seismic velocity in bedrock is a by-product of refraction statics analyses, which has rarely been fully exploited to constrain shallow geological interpretation. Local minima in seismic velocity in bedrock are associated with faults, showing that subvertical features that do not produce observable reflections can also be mapped. Significant variations in seismic velocity also indicate variations in lithology or formation boundaries. Variations in overburden and weathering thicknesses are accurately defined at Gullbridge where the careful choice of shot–receiver configuration allows estimates of both lateral and vertical variations in the seismic velocities of glacial overburden. The information on overburden properties is of value in drift prospecting for minerals and in studies of Quaternary geology.
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Hasler, A., S. Gruber i W. Haeberli. "Temperature variability and offset in steep alpine rock and ice faces". Cryosphere 5, nr 4 (10.11.2011): 977–88. http://dx.doi.org/10.5194/tc-5-977-2011.
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Abstract. The thermal condition of high-alpine mountain flanks can be an important determinant of climate change impact on slope stability and correspondingly down-slope hazard regimes. In this study we analyze time-series from 17 shallow temperature-depth profiles at two field sites in steep bedrock and ice. Extending earlier studies that revealed the topographic variations in temperatures, we demonstrate considerable differences of annual mean temperatures for variable surface characteristics and depths within the measured profiles. This implies that measurements and model related to compact and near-vertical bedrock temperatures may deviate considerably from conditions in the majority of bedrock slopes in mountain ranges that are usually non-vertical and fractured. For radiation-exposed faces mean annual temperatures at depth are up to 3 °C lower and permafrost is likely to exist at lower elevations than reflected by estimates based on near-vertical homogeneous cases. Retention of a thin snow cover and ventilation effects in open clefts are most likely responsible for this cooling. The measurements presented or similar data could be used in the future to support the development and testing of models related to the thermal effect of snow-cover and fractures in steep bedrock.
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Hasler, A., S. Gruber i W. Haeberli. "Temperature variability and thermal offset in steep alpine rock and ice faces". Cryosphere Discussions 5, nr 2 (1.03.2011): 721–53. http://dx.doi.org/10.5194/tcd-5-721-2011.
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Abstract. The thermal condition of high-alpine mountain flanks can be an important determinant of climate change impact on slope stability and correspondingly down-slope hazard regimes. In this study we analyze new time-series from 17 shallow temperature-depth profiles at two field sites in steep bedrock and ice. Extending earlier studies that revealed the topographic variations in temperatures, we demonstrate considerable differences of annual mean temperatures for variable surface characteristics and depths within the measured profiles. This implies that measurements and models related to compact and near-vertical bedrock temperatures may deviate considerably from conditions in the majority of bedrock slopes in mountain ranges that are usually non-vertical and fractured. For radiation-exposed faces, for instance, mean annual temperatures at depth are up to 3 °C lower and permafrost is likely to exist at lower elevations than reflected by current estimates based on the near-vertical case. Retention of thin snow cover and ventilation effects in open clefts are most likely responsible for this cooling. The presented or similar data could be used in the future to support the development and testing of models related to the thermal influence of snow-cover and fractures in steep bedrock. This would allow generalizing the here-presented findings.
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Pilon, P. E., i K. W. F. Howard. "Contamination of Subsurface Waters by Road De-icing Chemicals". Water Quality Research Journal 22, nr 1 (1.02.1987): 157–72. http://dx.doi.org/10.2166/wqrj.1987.012.
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Abstract The application of road de-icing chemicals to urban and rural roads in southern Ontario represents a serious potential source of shallow subsurface contamination. These chemicals are highly soluble and are readily mobilized by surface water run-off. This run-off can subsequently enter the soil zone and migrate through the shallow subsurface resulting in degradation of groundwater quality in the underlying aquifer. Recent work has investigated the extent to which the inorganic constituents of road de-icing chemicals constitute a threat to groundwater in the shallow subsurface environment. This study has focused on a) determining the extent to which road de-icing chemicals are accumulating in the shallow subsurface; b) identifying diagnostic chemical parameters which will enable conclusive contaminant source identification; and c) assessing rates of road de-icing contaminant migration. Fifteen field sites were selected to sample sediments adjacent to urban and rural roads. A total of forty seven interstitial water samples were submitted for major ion (Na, K, Mg, Ca, Cl, SO4, HCO3, NO3), minor ion (F, I, Br), pH, electrical conductivity and trace constituent analyses. Preliminary results indicate that the shallow subsurface adjacent to the urban road sites contain considerably elevated Na, Cl, Ca, and Mg. Interstitial waters from urban road sites may contain from 103 to 104 mg/L Cl and 103 mg/L Na as compared to less than 102 mg/L Cl and less than 102 mg/L Na for interstitial waters sampled from rural road sites and park locations. The ratio I/Cl exhibits potential as a diagnostic indicator of source origin. Interstitial waters contaminated by road salt regularly show I/Cl ratios two orders of magnitude lower than I/Cl ratios for saline bedrock waters.
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Jakšová, Patrícia, Peter Ľuptáčik i Dana Miklisová. "Distribution of Oribatida (Acari) along a depth gradient in forested scree slopes". Subterranean Biology 31 (8.07.2019): 29–48. http://dx.doi.org/10.3897/subtbiol.31.36241.
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Mesovoid shallow substratum (MSS) of scree slopes constitutes a transition habitat between the soil and the network of voids in the vadose zone of a bedrock massif. In the present study, the vertical distribution of oribatid communities along a depth of 95 cm was studied at five forested MSS sites in the Western Carpathians, Slovakia. The sites differed in type of bedrock, topography and gradient of the microclimate and nutrients content. In all, 909 specimens were captured in subterranean traps exposed for one year. Most Oribatida represented edaphic forms, and their presence in the depth profile of the screes was accidental. Pantelozetes cavatica (Kunst, 1962) was the only species closely linked to deep subterranean environments found in the deeper part of the single limestone site studied. Species richness and the activity of oribatids along the scree profile at the sites clearly reflected the content of organic carbon in the soil substratum. The communities had very low numbers of individuals and low species richness at three sites with soil pH < 7 and organic carbon content in the upper soil layer ≤ 10%. However, they differed markedly in internal temperature dynamics. The other two sites, with a slightly alkaline soil pH and a higher carbon content, showed distinctly higher activity and a relatively uniform pattern of oribatid distribution across the depth profile. The soil pH and organic carbon content in the topsoil layer were substantial factors that determined the Oribatida diversity and vertical distribution in the forested screes.
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Bergdahl, Dale R., Paul E. Sendak, Donald R. Tobi, James R. Bove i Louise M. Tritton. "Incidence of Annual Canker of Sugar Maple Studied with the Aid of a Geographic Information System". Northern Journal of Applied Forestry 19, nr 2 (1.06.2002): 73–79. http://dx.doi.org/10.1093/njaf/19.2.73.
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Abstract Sugar maples (Acer saccharum Marsh) ≥ 2.0 in. dbh were evaluated for incidence of annual canker caused by Fusarium spp. A total of 1,880 trees were evaluated from 73 plots located on 635 ac of privately owned northern hardwood forest in north central Vermont. About 12% of the trees were dead and one-fourth of both living and dead trees had annual canker. A logistic regression model was used to assess the role of soil-site characteristics related to the incidence of annual cankering. Probability estimates from the estimated regression equation were used to generate a map of annual canker risk. The generality of the results obtained here are untested and need to be applied to a more extensive area for validation. However, the technique for forest disease risk assessment could have wide application. We found annual canker was more common on sites that maintained a high number of stems per acre, on sites that were shallow to bedrock, and on sites that were dominated by sugar maple. We believe these findings suggest that sites that have shallow soils that include sugar maple probably should not be managed to encourage sugar maple. Sugar maple probably should be managed in stands that contain ample stocking of other northern hardwood species, and cultural practices that encourage maple over other species probably should be avoided.
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Wagner, Thomas, Alexander Brodacz, Karl Krainer i Gerfried Winkler. "Active rock glaciers as shallow groundwater reservoirs, Austrian Alps". Grundwasser 25, nr 3 (19.06.2020): 215–30. http://dx.doi.org/10.1007/s00767-020-00455-x.
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Abstract Rock glaciers are the most prominent landforms of alpine permafrost and comprise complex shallow aquifer systems in (high) alpine catchments. Recession analyses of groundwater discharge of four active rock glaciers that contain permafrost ground ice show that they have a base flow component of the order of a few liters per second, similar to that of a relict rock glacier in which permafrost ground ice is absent. This is related to an unfrozen (fine-grained) base layer with a thickness of about 10 m. Based on a threshold analysis of precipitation events and event water discharge, depressions atop the bedrock or the permafrost table seem to play only a minor role in storing groundwater. This important finding has rarely been documented, but is highly relevant for optimal groundwater resources management in sensitive (high) alpine catchments and ecosystems. All the rock glaciers analyzed here are located in the Austrian Alps and represent the nationwide sites where suitable discharge data are available. The analysis highlights the hydrogeological importance of these discrete permafrost-derived debris accumulations as complex shallow groundwater bodies with important—but limited—storage and buffer capabilities.
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Miles, D. W. R., i F. J. Swanson. "Vegetation composition on recent landslides in the Cascade Mountains of western Oregon". Canadian Journal of Forest Research 16, nr 4 (1.08.1986): 739–44. http://dx.doi.org/10.1139/x86-132.
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Shallow, rapid landslides are common events and significant causes of vegetation disturbance in the Pacific Northwest. Landslides remove surface soil and above- and below-ground biomass from steep slopes and deposit them downslope or in streams. Vegetation cover and frequency were sampled on 25 landslides aged 6–28 years in the Cascade Mountains of western Oregon. Landslides sampled were debris avalanches ranging in surface area from 36 to 1287 m2, in elevation from 460 to 1100 m, and in slope from 40 to 173%. The landslides originated in undisturbed forests, recently harvested tracts of timber, road cuts, and road fills. Substrates within landslide areas were separated into five types and the vegetation cover was estimated for each: bedrock, 19%; secondary erosion, 25%; primary scar, 51%; secondary deposition, 57%; primary deposition, 71%. Vegetation cover averaged 51% overall and cover ranged from 7 to 88% among landslide sites. No relation between landslide age and vegetation cover was established. Pseudotsugamenziesii (Mirb.) Franco was the most common tree species overall and dominated all substrates except bedrock, where no single tree species occurred on more than 20% of the plots. Rubusursinus Cham. & Schlecht. was the most common shrub species on all substrates. Anaphalismargaritacea (L.) B & H and Trientalislatifolia Hook, were the most common herb species on all substrates except bedrock, where annual Epilobium spp. were most common.
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Barker, James F. "Volatile Aromatic and Chlorinated Organic Contaminants in Groundwater at Six Ontario Landfills". Water Quality Research Journal 22, nr 1 (1.02.1987): 33–48. http://dx.doi.org/10.2166/wqrj.1987.003.
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Abstract Studies of the migration of organic contaminants in shallow aquifers impacted by landfill leachate at six sites in Ontario are reported. Three sites are located on very permeable sand deposits, one on less permeable sand till and two on fractured sedimentary bedrock. The migration rate and persistence of volatile, one-and-two carbon, halogenated hydrocarbons (halocarbons) and volatile aromatic hydrocarbons are emphasized. These compounds are ubiquitous in sanitary landfill leachates and are quite mobile in groundwater. They are at very low concentrations (less than 5 ppb each) at the Borden landfill site, where most waste was burned before landfilling. At the Woolwich site, volatile halocarbons are found at very low concentrations (less than 0.5 ppb each) up to one kilometer from the site, indicating that they may be very mobile and persistent in this aquifer. Attenuation, probably due mainly to dispersion, has resulted in only sub-ppb concentrations persisting beyond two hundred meters of the site. The contaminant plume at North Bay has been discharging to the surface about eight hundred meters from the site for a number of years. Some mobile volatile organics, therefore, are found throughout the plume. Halo-carbons do not persist and some aromatics appear to be undergoing biodegradation as well. For these and other contaminants, dramatic attenuation is observed within the eight hundred meter plume, probably as the result of dispersion. Groundwater velocities in the less-permeable sand and sand till at the new Borden site are much lower than in the other aquifers, so contaminants have only migrated perhaps two hundred meters laterally. Volatile halocarbons may be migrating at the groundwater velocity, while some retardation of aromatics may be occurring. However, the erratic contaminant distribution complicates the consideration of contaminant migration. Contaminant distributions are irregular in fractured bedrock at the Bay-view and Hamilton sites. The irregular and generally low concentration of halocarbons, coupled with the generally-poor background water quality in these bedrock flow systems, makes the definition of the zone of contamination at these sites very difficult. Although these low-porosity carbonate/ shale bedrock systems could distribute leachate contamination through a large volume of rock, it is encouraging to note the rather restricted zone of clearly-impacted groundwater. The major, mobile organic contaminants at the Hamilton site are the volatile aromatic hydrocarbons. Recognition of only-slightly-impacted groundwater at this site is complicated by the occurrence of these organics at ppb levels in apparently uncontaminated, background groundwater. Temporal variations, over weeks and years, are found for all contaminants at these sites. Input from the landfill appears to be temporally variable and so is a major cause of subsequent variations within the leachate plume. The processes of dispersion, which smoothes such variations at some sites (Borden), does not appear to be effective at damping temporal variability along the plume at North Bay nor in the fractured-bedrock systems.
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Rudy, Ján, Michal Rendoš, Peter Ľuptáčik i Andrej Mock. "Terrestrial isopods associated with shallow underground of forested scree slopes in the Western Carpathians (Slovakia)". ZooKeys 801 (3.12.2018): 323–35. http://dx.doi.org/10.3897/zookeys.801.24113.
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The shallow underground of forested scree slopes represents a little-studied subterranean biotope. In this paper, species diversity and depth distribution of terrestrial isopod communities studied in the depth profile (5–95 cm from the surface) of eight forested scree slopes in the Western Carpathians (Slovakia) is discussed. The southern edge of the Western Carpathians where the study sites are located represents the northernmost limit of distribution of obligate subterranean fauna in Europe. The sites differ from each other in type of bedrock, forest composition, slope aspect, and altitude. To sample isopods, a set of three subterranean pitfall traps consisting of a plastic cylinder (Ø 110 mm) and ten plastic cups was buried in each studied scree slope. In total, 252 isopods belonging to eleven species were sampled (1–5 species per site). Of the species found, the blind and depigmented Mesoniscusgraniger was the sole species closely associated with deeper parts of the depth profile and was present in most of the sites studied. Another ten species were represented by a small number of individuals and their occurrence deeper in the scree slope profile was rather accidental. A comparison between winter and summer periods indicates apparent differences in seasonal activities of isopods. Ethylene glycol seems to be more appropriate fixative solution for trapping isopods than formaldehyde.
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Haeberli, Wilfried, Regula Frauenfelder, Andreas Kääb i Stephan Wagner. "Characteristics and potential climatic significance of “miniature ice caps” (crest- and cornice-type low-altitude ice archives)". Journal of Glaciology 50, nr 168 (2004): 129–36. http://dx.doi.org/10.3189/172756504781830330.
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AbstractLong-term ice-core records of Alpine glaciers are usually taken from cold-firn areas at high altitudes, as on Mont Blanc and Monte Rosa. Perennial ice bodies at lower altitudes, however, also bear information about the past. Recent findings from the remains of such ice (the Oetztal iceman found in Austria; wooden bows at Lötschen Pass, Switzerland) clearly indicate the hitherto little-recognized fact that small, more-or-less static perennial ice bodies which are cold and frozen to the underlying bedrock may contain very old ice and, hence, important palaeoclimatic information about warm periods with minimum ice extent in the Alps. Since autumn 1998, investigations have been initiated on a crest-type location or “miniature ice cap” at Piz Murtèl, Engadine, Swiss Alps. First results from shallow drilling, temperature data-logging, geodetic surveying, visual observation, finite-element modelling of simplified basic two-dimensional configurations and comparison to earlier measurements at similar sites provide promising perspectives concerning a little-studied phenomenon with considerable scientific-environmental research potential. Specific characteristics of the investigated site, and probably of many other comparable mountain sites, are: cold ice (about –4°C at 10 m depth), no basal sliding, small mass turnover, striking lack of a firn zone, accumulation mainly by superimposed ice, and direct access to old layers (centuries, millennia?) at the ice/bedrock interface.
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Allen, D. M., i M. Suchy. "Geochemical evolution of groundwater on Saturna Island, British Columbia". Canadian Journal of Earth Sciences 38, nr 7 (1.07.2001): 1059–80. http://dx.doi.org/10.1139/e01-007.
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A detailed geochemical study of surface waters, spring waters, and groundwaters was undertaken to examine the geochemical evolution of groundwater on Saturna Island, British Columbia. The purpose of the study was to characterize the nature and occurrence of saline waters and to provide insight on chemical processes that lead to salinization in the fractured sedimentary bedrock aquifers of this small island. Major ion chemistry shows that groundwater is recharged locally but mixes with saline waters that occur at depth or near the coast. Simple mixing is complicated by cation exchange (between calcium-rich waters and sodium-rich exchange sites offered by mudstone beds) and results in a spatially variable hydrochemical composition that is dependent on the island topography and geological framework (structural, sedimentological, and glacial), in combination with groundwater use patterns. Sodium, present at exchange sites, is speculated to be a remnant of ocean water intrusion during the Pleistocene, when the island was submerged. As a result of its high mobility and conservative nature, chloride (and sulphate) has been flushed from the shallow bedrock during a process of natural desalinization but may remain trapped in the pores and fractures at depth. Modern salt-water intrusion, brought about by increased development on the island, is now competing with natural desalinization along the coast and has left many drinking-water supplies contaminated.
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Schaetzl, Randall J., Christopher Baish, Patrick M. Colgan, Jarrod Knauff, Thomas Bilintoh, Dan Wanyama, Michelle Church, Kevin McKeehan, Albert Fulton i Alan F. Arbogast. "A sediment-mixing process model of till genesis, using texture and clay mineralogy data from Saginaw lobe (Michigan, USA) tills". Quaternary Research 94 (21.02.2020): 174–94. http://dx.doi.org/10.1017/qua.2019.82.
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AbstractWe present a sediment-mixing process model of till genesis based on data from surface tills of the Saginaw lobe terrain in lower Michigan. Our research uses a spatial approach to understanding glacial landsystems and till genesis. We sampled calcareous till at 336 upland sites and at 17 sites in lacustrine sediment of the Saginaw Lake plain. The loamy tills have bimodal grain-size curves, with a fine-texture mode near the silt–clay boundary and a sand mode. Spatial grouping analysis suggests that tills can be divided into six groups, each with different textures and clay mineral compositions that vary systematically down-ice. The similarity among groups with respect to the silt–clay mode and clay mineralogy argues for a common origin for the fines—illite-rich lacustrine sediment of the Saginaw Lake plain. Fine-textured sediments were probably entrained, transported, and deposited down-ice as till, which also becomes sandier and enriched in kaolinite, reflecting increasing mixing with shallow sandstone bedrock with distance from the lacustrine clay source. Clayey tills on the flanks of the Saginaw terrain may reflect proglacial ponding against nearby uplands. A process model of progressive down-ice mixing of preexisting fine lake sediments with crushed/abraded sandstone bedrock helps to better explain till textures compared with a purely crushing/abrasion process model.
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Dale, Janis E., i Kent Leontowich. "Sediments and Biota of the Marine Coastal Zone of Igloolik Island, Nunavut". Géographie physique et Quaternaire 60, nr 1 (19.09.2007): 63–80. http://dx.doi.org/10.7202/016365ar.
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Abstract Few studies in arctic Canada have combined research on both the physical marine environment and benthic invertebrates. This is the first detailed study of the oceanographic conditions and distribution of sediments and biota in the intertidal and subtidal zones of Igloolik Island, Nunavut. Oceanographic measurements (temperature, salinity, dissolved oxygen, turbidity), and sediment and biological sampling were undertaken over two summers (1999, 2002). Intertidal zones are underlain by bedrock with a thin veneer of gravel with a very poorly sorted fine matrix and devoid of benthic invertebrates, due to harsh environmental conditions. Ninety-six benthic invertebrates species were identified in the subtidal zone of Turton Bay, a shallow embayment of Igloolik Island that opens to the south into Hooper Inlet. Oceanographic conditions were similar throughout Turton Bay. The shallow depth of Turton Bay (<25 m) and open fetch to the south means that the bay water is well mixed throughout during the ice-free period. Variations in species, abundances and densities result from local conditions and substrate characteristics. Subtidal areas with unconsolidated substrates have abundant and diversified benthic fauna, whereas those with consolidated substrates have more limited species dominated by epifauna. The greatest abundances and densities occur at the deepest sites with the finest sediments and deposit-feeding species. The shallow subtidal zone (<5 m) is characterized by a thin sandy surface veneer overlying bedrock. It is an extension of the intertidal zone and is much affected by ice action during break-up with reduced numbers of marine fauna. High densities of opportunistic and pollution tolerant species along transects in Turton Bay are explained by the outflow and seepage from the sewage lagoon and dumpsites proximal to these transects.
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Papadopoulos, I., C. Papazachos, A. Savvaidis, N. Theodoulidis, F. Vallianatos i P. Tsourlos. "Results for the shallow structure of the broader region of Chania by HVSR measurements of ambient noise and their validation using simulation of ambient noise and independent geological information." Bulletin of the Geological Society of Greece 47, nr 3 (21.12.2016): 1201. http://dx.doi.org/10.12681/bgsg.10976.
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The city of Chania is located at the Western-North part of the island of Crete. It is mostly built over Neogene sediments of unknown thickness. In the southern part of the city the Chania basin is developed, filled mainly by Quaternary deposits overlyingthe deep Neogene sediments. In this complex geological setting, we conducted over 200 single station measurements of ambient noise, aiming to estimate the predominant frequency of the subsurface formations. The obtained results for the HVSR data show a different behavior between sites located on Neogene and Quaternarydeposits. In general, Neogene sediments show a single peak at low frequencies (below 1Hz, typically in the range 0.4-0.6Hz), indicating a very thick layer overlying the bedrock (Trypalion and Plattenkalk limestones). On the other hand, measurements at Quaternary deposits show two peaks, with the first one similar to the Neogene formations, while the second one is identified at higher frequencies, typically~0.8-4.0 Hz. Simulation of ambient noise 1-D models show a good correlation between the experimental and theoretical HVSR curves, especially when the initial model consists of two layers (typically Neogene sediments overlying high-velocity bedrock formations) with a clear identification of the lower frequency HVSR peak, while for three layered models (typically Quaternary sediments and underlying softerNeogene and Neogene/bedrock high-velocity formations) results are more complicated, although both HVSR frequencies can be partly reconstructed.
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Ermert, Laura A., Enrique Cabral-Cano, Estelle Chaussard, Darío Solano-Rojas, Luis Quintanar, Diana Morales Padilla, Enrique A. Fernández-Torres i Marine A. Denolle. "Probing environmental and tectonic changes underneath Mexico City with the urban seismic field". Solid Earth 14, nr 5 (23.05.2023): 529–49. http://dx.doi.org/10.5194/se-14-529-2023.
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Abstract. The sediments underneath Mexico City have unique mechanical properties that give rise to strong site effects. We investigated temporal changes in the seismic velocity at strong-motion and broadband seismic stations throughout Mexico City, including sites with different geologic characteristics ranging from city center locations situated on lacustrine clay to hillside locations on volcanic bedrock. We used autocorrelations of urban seismic noise, enhanced by waveform clustering, to extract subtle seismic velocity changes by coda wave interferometry. We observed and modeled seasonal, co- and post-seismic changes, as well as a long-term linear trend in seismic velocity. Seasonal variations can be explained by self-consistent models of thermoelastic and poroelastic changes in the subsurface shear wave velocity. Overall, sites on lacustrine clay-rich sediments appear to be more sensitive to seasonal surface temperature changes, whereas sites on alluvial and volcaniclastic sediments and on bedrock are sensitive to precipitation. The 2017 Mw 7.1 Puebla and 2020 Mw 7.4 Oaxaca earthquakes both caused a clear drop in seismic velocity, followed by a time-logarithmic recovery that may still be ongoing for the 2017 event at several sites or that may remain incomplete. The slope of the linear trend in seismic velocity is correlated with the downward vertical displacement of the ground measured by interferometric synthetic aperture radar, suggesting a causative relationship and supporting earlier studies on changes in the resonance frequency of sites in the Mexico City basin due to groundwater extraction. Our findings show how sensitively shallow seismic velocity and, in consequence, site effects react to environmental, tectonic and anthropogenic processes. They also demonstrate that urban strong-motion stations provide useful data for coda wave monitoring given sufficiently high-amplitude urban seismic noise.
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Islami, Nur, i Mitri Irianti. "Integrated Very Low Frequency and Geoelectrical Resistivity Methods to Study Possibility Shallow Groundwater Pathway in Bedrock Area". Journal of Physics: Conference Series 2049, nr 1 (1.10.2021): 012056. http://dx.doi.org/10.1088/1742-6596/2049/1/012056.
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Abstract Exploration of groundwater movement has a specific challenge in thick forest area and cover with the shallow hard rock. The use of active and passive geophysical method is needed for groundwater exploration. This study aims to explore the prospect of groundwater zone especially for the groundwater pathway in the area around the hot spring zone. Geoelectrical resistivity and very low frequency (VLF) methods were used with electrode spacing of 2 meter and reading stations of about 5 meter, respectively. The geoelectrical resistivity was carried out using the Wenner configuration in the sites around the hot spring. The results show that the VLF model indicates occurrence of the conductive zones at the depth of about 10 m. The geoelectrical resistivity data show the same pattern with the VLF image. These conductive zones which is appeared in the VLF model are indicating as the zone of groundwater water pathway from the source to the hot spring zones. The geoelectrical resistivity data also showed the same possibility of groundwater pathway.
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Gołębiowski, Tomisław, i Elżbieta Jarosińska. "Application of GPR and ERT methods for recognizing of gypsum deposits in urban areas". Acta Geophysica 67, nr 6 (8.10.2019): 2015–30. http://dx.doi.org/10.1007/s11600-019-00370-7.
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Abstract This paper presents the selected results of GPR (ground penetrating radar) and ERT (electrical resistivity tomography) surveys carried out on the sites in Poland where shallow karst forms were found in gypsum deposits. The aim of the surveys was the noninvasive detection of karst forms as well as weathered and fractured bedrock which may threaten the stability of the surface and, consequently, may cause damage to buildings, as well as overground and underground infrastructure. The geophysical surveys were conducted at a depth of only a few meters, i.e., to the depth of buildings foundations. GPR surveys were carried out in short-offset reflection profiling mode with standard orientation of the antennae set; however, on one site, different orientations of antennae were tested. During ERT surveys, different measurement arrays were applied in order to analyze which array was optimal for the detection of karst forms as well as weathered and fractured bedrock. Complex interpretation of geophysical surveys resulted in reduced ambiguity and revealed some regions, dangerous for surface stability. Due to the fact that gypsum deposits were investigated to the depth of maximum 10 m; therefore, hydrological processes were analyzed in the paper instead of hydrogeological processes.
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Milana, G., S. Barba, E. Del Pezzo i E. Zambonelli. "Site response from ambient noise measurements: New perspectives from an array study in Central Italy". Bulletin of the Seismological Society of America 86, nr 2 (1.04.1996): 320–28. http://dx.doi.org/10.1785/bssa0860020320.
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Abstract In this study, we used both spectral and array techniques to investigate microtremor characteristics in an urban area in Central Italy and to relate them to the properties of shallow geological structures. We made noise measurements for sites located on the various surface geological conditions that can be found in the town of Rieti. Both sediments and bedrock are present at the surface, and the transition zone between them is very narrow and well localized. Using a small area reduced the effects related to the poor knowledge about the distribution of noise sources; using spectral ratio techniques, a good image of resonance frequencies on the alluvial sediments was obtained. Moreover, the use of an array allowed to describe better the morphology of the bedrock and to study Rayleigh-wave dispersion. Starting from the obtained surface-wave dispersion curve, we calculated a velocity model producing both a theoretical dispersion relationship and resonance frequencies for sedimentary layers in good agreement with experimental data. Our work suggests that the use of array techniques can be very useful to increase the quality of microtremor data, giving new answers to microzoning problems.
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Rodríguez-Marek, Adrián, Jonathan D. Bray i Norman A. Abrahamson. "An Empirical Geotechnical Seismic Site Response Procedure". Earthquake Spectra 17, nr 1 (luty 2001): 65–87. http://dx.doi.org/10.1193/1.1586167.
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A simplified empirically based seismic site response evaluation procedure that includes measures of the dynamic stiffness of the surficial materials and the depth to bedrock as primary parameters is introduced. This geotechnical site classification scheme provides an alternative to geologic-based and shear wave velocity-based site classification schemes. The proposed scheme is used to analyze the ground motion data from the 1989 Loma Prieta and 1994 Northridge earthquakes. Period-dependent and intensity-dependent spectral acceleration amplification factors for different site conditions are presented. The proposed scheme results in a significant reduction in standard error when compared with a simpler “rock vs. soil” classification system. Moreover, results show that sites previously grouped as “rock” should be subdivided as competent rock sites and weathered soft rock/shallow stiff soil sites to reduce uncertainty in defining site-dependent ground motions. Results also show that soil depth is an important parameter in estimating seismic site response. The standard errors resulting from the proposed site classification system are comparable with those obtained using the more elaborate code-based average shear-wave velocity classification system.
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Huang, Huey-Chu, Tien-Han Shih, Cheng-Ta Hsu i Cheng-Feng Wu. "Estimation of Shear-Wave Velocity Structures in Taichung, Taiwan, Using Array Measurements of Microtremors". Applied Sciences 12, nr 1 (24.12.2021): 170. http://dx.doi.org/10.3390/app12010170.
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Near-surface S-wave velocity structures (VS) are crucial in site-effect studies and ground-motion simulations or predictions. We explored S-wave velocity structures in Taichung, the second-largest city in Taiwan by population, by employing array measurements of microtremors at a total of 53 sites. First, the fundamental-mode dispersion curves of Rayleigh waves were estimated by adopting the frequency–wavenumber analysis method. Second, the surface-wave inversion technique was used to calculate the S-wave velocity structures of the area. At many sites, observed phase velocities were almost flat, with a phase velocity of approximately 800–1300 m/s in the frequency range of 0.6–2 Hz. A high-velocity zone (VS of 900–1500 m/s) with a convex shape was observed at the shallow S-wave structures of these sites (depths of 50–500 m). On the basis of the inversion results, we constructed two-dimensional and three-dimensional contour maps to elucidate the variations of VS structures in Taichung. According to VS-contour maps at different depths, lowest S-wave velocities are found at the western coastal plain, whereas highest S-wave velocities appear on the eastern side. The S-wave velocity gradually decreases from east to west. Moreover, the S-wave velocity of the Tertiary bedrock is assumed to be 1500 m/s in the area. According to the depth-contour map (VS = 1500 m/s), the depths of the bedrock range from 250 m (the eastern part) to 1550 m (the western part). The thicknesses of the alluvium gradually decrease from west to east. Our results are consistent with the geology of the Taichung area.
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Chandran, Deepu, i P. Anbazhagan. "2D nonlinear site response analysis of typical stiff and soft soil sites at shallow bedrock region with low to medium seismicity". Journal of Applied Geophysics 179 (sierpień 2020): 104087. http://dx.doi.org/10.1016/j.jappgeo.2020.104087.
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Woch, Marcin, i Magdalena Hawryluk. "Flora of xerothermic sites of the Zachodniowołyńska Dolina Bugu Special area of conservation (Eastern Poland): The influence of habitat on rare grassland species". Archives of Biological Sciences 66, nr 1 (2014): 209–26. http://dx.doi.org/10.2298/abs1401209w.
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The aim of the investigation was to study the flora of grasslands within the Zachodniowo?y?ska Dolina Bugu Special Area of Conservation and to identify the types of habitats with the highest concentration of grassland species. In the years 2011-2012, floristic analyses covered the slopes of the valley of the Bug river, balks and places of shallow bedrock deposition, roadsides, as well as railway and earthwork sites. One hundred and fifty eight plant species belonging to 37 families were found. Though considered extinct in Polish flora, Dianthus collinus subsp. glabriusculus was discovered. Close to half of the recorded species (47%) were grassland taxa and 15% rare and/or protected plants, which make the studied area particularly valuable for the conservation of biodiversity. The fewest grassland plants occurred on habitats that are under the influence of agriculture, where the dominance of nitrophilous and herbicide resistant plant species was observed.
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Taylor, Elliott, i Doug Reimer. "SCAT SURVEYS OF PRINCE WILLIAM SOUND BEACHES – 1989 TO 2002". International Oil Spill Conference Proceedings 2005, nr 1 (1.05.2005): 801–6. http://dx.doi.org/10.7901/2169-3358-2005-1-801.
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ABSTRACT A SCAT survey in 2002 documented conditions at 39 selected survey sites where EVOS oil persisted in 1992, at the time the Federal and State On-Scene Coordinators determined that further cleanup activities would provide no net environmental benefit. The 2002 field survey found isolated occurrences of residual EVOS surface oil (SO) in the form of weathered asphalt pavement at 15 of the 39 sites. SO, expressed as a continuous oil cover, was less 0.2% of the surface area surveyed. Seven of the 39 sites and 815 (68%) of the total 1182 pits contained no residual SSO. SSO was found primarily in middle to upper intertidal locations, where it occurred in discontinuous ∼3cm thick bands 5–10 cm below the boulder/cobble or pebble/gravel veneer. Despite evidence of continued oil weathering, both at the surface and in the subsurface, it is clear that the natural cleaning processes at these particular locations are slow. The continued but slow weathering rates are a consequence of the oil being sequestered from the environment because it occurs in mixed (coarse and fine) sediments on beaches where boulders and outcrops, shallow bedrock asperities, or boulder-armoring limit effective physical weathering action.
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Booth, Colin J., Alan M. Curtiss, Philip J. Demaris i Robert A. Bauer. "Site-specific variation in the potentiometric response to subsidence above active longwall mining". Environmental and Engineering Geoscience 6, nr 4 (1.11.2000): 383–94. http://dx.doi.org/10.2113/gseegeosci.6.4.383.
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Abstract Longwall underground coal mining produces major changes in the hydraulic properties and groundwater levels of overlying shallow aquifers because of the fracturing associated with mine subsidence. Many aspects of these impacts remain unclear and unpredictable, particularly the variations in response between different sites. Our detailed, long-term studies of subsidence strains and hydraulic responses at sites in Illinois address this and other aspects of the conceptual model. At a study site in Saline County, inconsistent permeability changes and large rapid head drops, without significant recovery, were observed in a low transmissivity sandstone over an active longwall panel. Corresponding head changes in overlying glacial drift units reflected localized drainage from the drift to the bedrock. In comparison to our earlier study at a site in Jefferson County, Illinois, in which full recovery occurred in a moderately transmissive sandstone aquifer affected by longwall mining, the Saline site illustrates the importance of local hydrogeologic characteristics, particularly variations in transmisivity and continuity with recharge sources, in controlling site-specific responses to longwall mining.
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Nicolson, J. A. "Alternate Strip Clearcutting in Upland Black Spruce: V. The Impact of Harvesting on the Quality of Water Flowing from Small Basins in Shallow-soil Boreal Ecosystems". Forestry Chronicle 64, nr 1 (1.02.1988): 52–58. http://dx.doi.org/10.5558/tfc64052-1.
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Streams flowing from six small basins (100-450 ha), dominated or originally dominated by black spruce stands growing on sites with shallow soil over bedrock, were monitored for seven years (1978-1984) near Lake Nipigon, Ontario. Three basins were left uncut. Three basins were harvested, one by patch-cutting, one by clearcutting, and one by stripcutting (in a three-cut pattern, with cutting in 1977, 1979 and 1981). Comparison of streamwater from harvested and uncut basins indicated a greater water yield from the harvested basins, as well as differences in several chemical parameters. Specific conductance, alkalinity, Ca2+, Mg2+, K+, Na+, and [Formula: see text] concentration increases were statistically significant. Nitrate-nitrogen and total nitrogen (TN) levels generally decreased, the former significantly; pH, [Formula: see text], Cl−, [Formula: see text], [Formula: see text] and total phosphorus (TP) changes were not signficiant.
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Béland, Martin, i Yves Bergeron. "Height growth of jack pine (Pinushanksiana) in relation to site types in boreal forests of Abitibi, Quebec". Canadian Journal of Forest Research 26, nr 12 (1.12.1996): 2170–79. http://dx.doi.org/10.1139/x26-246.
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A combination of surface deposit and moisture regime class was used to investigate the utility of site type as a predictor of jack pine growth in northwestern Quebec. Height–age curves produced from stem analyses of dominant trees from 96 sample plots produced three jack pine (Pinusbanksiaina Lamb.) productivity classes. The low productivity class includes moderately dry shallow tills, shallow organic deposits over bedrock, and fluvioglacial sands with moisture regime classes moderately dry and fresh. Moderately dry to very moist deep tills and moderately dry to moist clays are classified as having high and very high productivity, respectively. The large difference in height growth between these latter two groups and the low productivity class precluded the definition of a moderate productivity class. The form of the height-growth curves was very similar among site types except for sandy, moderately dry sites, which showed a growth delay at young ages. On dry sites, particularly on well-drained tills, density and basal area were higher than on clay sites. Although volume yield of natural stands on tills and clays would thus be similar, it would likely be spread among a greater number of stems on tills. There was little difference in site index between natural jack pine growing on clays and tills. The low nutrient and moisture requirements and strong taproot of jack pine could explain why soil depth and bulk density are more important than soil richness. Although site type, expressed as a combination of surface deposit and moisture regime class, may be more detailed than needed, it provided an adequate prediction of potential jack pine productivity.
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Anbazhagan, P., Parihar Aditya i H. N. Rashmi. "Amplification based on shear wave velocity for seismic zonation: comparison of empirical relations and site response results for shallow engineering bedrock sites". Geomechanics and Engineering 3, nr 3 (25.09.2011): 189–206. http://dx.doi.org/10.12989/gae.2011.3.3.189.
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Khaheshi Banab, Kasgin, i Dariush Motazedian. "On the Efficiency of the Multi-Channel Analysis of Surface Wave Method for Shallow and Semi-Deep Loose Soil Layers". International Journal of Geophysics 2010 (2010): 1–13. http://dx.doi.org/10.1155/2010/403016.
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The multi-channel analysis of surface waves (MASWs) method was used to obtain the shear wave velocity variations through near surface (depth < 30 m) and semi-deep (30 m < depth < 100 m) soil layers in the city of Ottawa, Canada. Sixteen sites were examined to evaluate the capability of the active and passive MASW methods for cases where the shear wave velocity(Vs)contrast between very loose soil (Vs< 200 m/s) and very firm bedrock (Vs> 2,300 m/s) is very large. The MASW velocity results compared with those of other geophysical approaches, such as seismic reflection/refraction methods and borehole data, where available, mostly confirming the capability of the MASW method to distinguish the high shear wave velocity contrast in the study area. We have found that, of the inversion procedures of MASW data, the random search inversion technique provides better results than the analytical generalized inversion method.
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ADIGUN, ALAGBE OLUFEMI, AROGUNDADE ADEWALE MUIDEEN i AWALLAH MUSA ADESOLA. "DELINEATION OF SHALLOW FLOODPLAIN AQUIFERS FOR IRRIGATION PURPOSES OVER A FLOODPLAIN AT AULE, AKURE SOUTHWESTERN NIGERIA". International Journal of Agriculture and Environmental Research 08, nr 02 (2022): 209–50. http://dx.doi.org/10.51193/ijaer.2022.8202.
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Geophysical investigation involving the use of Electrical Resistivity method using Modified Wenner Array Configuration has been adopted for shallow groundwater potential evaluation over a floodplain at AULE, Akure southwestern Nigeria for irrigation purposes. The research presents the result from the quantitative interpretation of forty eight vertical electrical sounding (VES) obtained from the survey area which has helped in the identification of aquiferous units and has provided an understanding of aquifer characteristics especially the thickness and depth to fractured zones which are required for locating points with high potentials for groundwater occurrence. The Vertical Electrical Sounding technique result delineated three to six (3-6) subsurface geologic layers (top soil, clay, clay, weathered layer, partly weathered layer and bedrock) with different depth ranges (0.04m to 10.0m). The lithology of the subsurface strata is mainly clay (expansive clay) which justifies the dominance of low resistivity values and explains why the runoff water via flood doesn’t infiltrate the soil. The overburden thickness and aquifer resistivity were used in classifying the groundwater potential of the study area. Areas having moderate overburden with thickness between 5m and 10m with weathered layer above 4 Ωm such as VES 1, 3, 13, 28, 32, 39, 40, 41, 43 and 44 are delineated to be promising sites for shallow wells.
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Montalva, Gonzalo A., Francisco J. Chávez-Garcia, Andrés Tassara i Darío M. Jara Weisser. "Site Effects and Building Damage Characterization in Concepción after the Mw 8.8 Maule Earthquake". Earthquake Spectra 32, nr 3 (sierpień 2016): 1469–88. http://dx.doi.org/10.1193/101514eqs158m.
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The influence of site effects on seismic demand was studied in Concepción to explain the observed damages suffered by engineered structures during the 2010 Mw 8.8 Maule, Chile, earthquake. Shallow shear-wave velocity ( V S), site period, and gravity measurements were used to assess site effects. The three-dimensional (3-D) basin shape was inverted from gravity values. Predominant period shows a good correlation with bedrock depth, suggesting that V S of soil is relatively uniform throughout the city. This was confirmed by direct V S measurements at 17 sites throughout the city. The irregular distribution of damage suggests that V S30 is not a good proxy for damage distribution in Concepción. In contrast, we observe dependence with basin thickness, site period, and estimated PGV for buildings with high vulnerability. Most low-vulnerability structures showed no damage regardless of site conditions and intensity measures. Our results indicate that site effects contributed to structural damage in vulnerable structures and these effects were primarily controlled by basin depth.
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Bajtoš, Peter, Peter Malík i Radovan Černák. "Estimation of specific yield in bedrock near-surface zone of hilly watersheds by examining the relationship between base runoff, storage and groundwater level". Mineralia Slovaca 55, nr 1 (31.07.2023): 85–102. http://dx.doi.org/10.56623/ms.2023.55.1.6.
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A catchment-scale method for estimation of specific yield (Sy) in the zone of groundwater level fluctuation is proposed. It is applicable to hilly watersheds, where deep groundwater discharge – not drained by local streams as baseflow – is small and can be neglected. Therefore, it is mostly employable for bedrock flow systems, dominated by shallow unconfined fractured rock aquifers. Method provides an estimate of specific yield (Sy) by combined analysis of streamflow recession, storage/runoff relationship and groundwater level fluctuation (Q-S-H). For groundwater storage (S) values evaluation, river discharge (Q) master recession curves are constructed and interpreted. The method produces as more reliable results as number of groundwater level observation sites increases. As example, it is demonstrated at the Levočský potok Brook watershed (Western Carpathians, Slovakia), built by fracture porosity dominated Paleogene sediments. Estimated characteristic Sy value is from the interval 0.001–0.002 and 0.002–0.005 for low and medium storage/runoff conditions – or bottom and middle part of GWL fluctuation zone – respectively.
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Thackray, Glenn, Mark Zellman, Jason Altekruse, Bruno Protti i Harrison Colandera. "Shallow Seismic Investigation of the Teton Fault". UW National Parks Service Research Station Annual Reports 37 (1.01.2014): 2–10. http://dx.doi.org/10.13001/uwnpsrc.2014.4033.
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Preliminary results from seismic data collected at two sites on the Teton fault reveal shallow sub-surface fault structure and a basis for evaluating the post-glacial faulting record in greater detail. These new data include high-resolution shallow 2D seismic refraction and Interferometric Multi-Channel Analysis of Surface Waves (IMASW) (OâConnell and Turner 2010) depth-averaged shear wave velocity (Vs). The Teton fault, a down-to-the east normal fault, is expressed as a distinct topographic escarpment along the base of the eastern front of the Teton Range in Wyoming. The average fault scarp height cut into deglacial surfaces in several similar valleys and an assumed 14,000 yr BP deglaciation indicates an average postglacial offset rate of 0.82 m/ka (Thackray and Staley, in review). Because the fault is located almost entirely within Grand Teton National Park (GTNP), and in terrain that is remote and difficult to access, very few subsurface studies have been used to evaluate the fault. As a result, many uncertainties exist in the present characterization of along-strike slip rate, down-dip geometry, and rupture history, among other parameters. Additionally, questions remain about the fault dip at depth. Shallow seismic data were collected at two locations on the Teton fault scarp to (1) use a non-destructive, highly portable and cost-effective data collection system to image and characterize the Teton fault, (2) use the data to estimate vertical offsets of faulted bedrock and sediment, and (3) estimate fault dip in the shallow subsurface. Vs data were also collected at three GTNP facility structures to provide measured 30 m depth-averaged Vs (Vs30) for each site. Seismic data were collected using highly portable equipment packed into each site on foot. The system utilizes a sensor line 92 m long that includes 24 geophones (channels) at 4 m intervals. At both the Taggart Lake and String Lake sites, P-wave refraction data were collected spanning the fault scarp and perpendicular to local fault strike, as well as IMASW Vs seismic lines positioned on the hanging wall to provide Vs vs. Depth profiles crossing and perpendicular to the refraction survey lines. The Taggart Lake and String Lake 2D P-wave refraction profile and IMASW Vs plots reveal buried velocity structure that is vertically offset by the Teton fault. At Taggart Lake, we interpret the velocity horizon to be the top of dense glacial sediment (possibly compacted till), which is overlain by younger, slower, sediments. This surface is offset ~13 m (down-to-the-east) across the Teton fault. The vertical offset is in agreement with the measured height of the corresponding topographic scarp (~12 - 15 m). Geomorphic analysis of EarthScope (2008) LiDAR reveals small terraces, slope inflections and an abandoned channel on the footwall side of the scarp. At String Lake, the shallow buried velocity structure is inferred as unconsolidated alluvium (till, colluvium, alluvium); this relatively low velocity zone (
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Sokolov, Vladimir Yu. "Spectral parameters of the ground motions in Caucasian seismogenic zones". Bulletin of the Seismological Society of America 88, nr 6 (1.12.1998): 1438–44. http://dx.doi.org/10.1785/bssa0880061438.
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Abstract A collection of ground-motion recordings including accelerograms of the mainshock of the 7 December 1988, Spitak earthquake (M = 6.9, Northern Armenia) has been obtained during the 1988 to 1990 strong-ground-motion network operation. This region of the Caucasus still has a poor database for strong-ground-motion prediction, but the data studied here form a basis for source scaling and attenuation relation study. The results show that the acceleration spectra of shear waves recorded at rock sites can be modeled accurately by the Brune source model using a stress parameter of 50 to 100 bar (Spitak area) and 200 bar (events to the North from the Spitak area), and cutoff frequency fmax = 7 to 10 Hz. The anelastic attenuation Q of spectral amplitudes with distance may be described by the form published by Boore (1987) Q = 29.4 [1 + (f/0.3)2.9]/(f/0.3)2 up to distances R = 70 km. The comparison of modeled bedrock spectra with observed data (registered at shallow soil deposits) allowed the author to estimate the local site response in terms of frequency-dependent amplification functions. The generalized regional amplification function was used to predict ground motion in conditions of shallow soils. Stochastic simulation of ground motions (peak ground acceleration and response spectra) using the obtained models of source spectra and attenuation shows good agreement with observed data.
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Talukder, Mohammad Kamruzzaman, Philippe Rosset i Luc Chouinard. "Reduction of Bias and Uncertainty in Regional Seismic Site Amplification Factors for Seismic Hazard and Risk Analysis". GeoHazards 2, nr 3 (3.09.2021): 277–301. http://dx.doi.org/10.3390/geohazards2030015.
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Site amplification factors in National Building Codes are typically specified as a function of the average shear wave velocity over the first 30 m (Vs30) or site class (A, B, C, D and E) for defined ranges of Vs30 and/or ranges of depth to bedrock. However, a single set of amplification factors may not be representative of site conditions across the country, introducing a bias in seismic hazard and seismic risk analyses. This is exemplified by significant differences in geological settings between East and West coast locations in North America. Western sites are typically characterized by lower impedance contrasts between recent surface deposits and bedrock in comparison to Eastern sites. In North America, site amplification factors have been derived from a combination of field data on ground motions recorded during West Coast earthquakes and numerical models of site responses that are meant to be representative of a wide variety of soil profiles and ground motions. The bias on amplifications and their impact on seismic hazards is investigated for the Montreal area, which ranks second for seismic risks in Canada in terms of population and hazard (PGA of 0.25 g for a 2475 years return period). Representative soil profiles at several locations in Montreal are analyzed with 1-D site response models for natural and synthetic ground motions scaled between 0.1 to 0.5 g. Since bedrock depths are typically shallow (<30 m) across the island, bedrock shear wave velocities have a significant influence on the impedance contrast and amplifications. Bedrock shear wave velocity is usually very variable due to the differences in rock formations, level of weathering and fracturing. The level of this uncertainty is shown to be greatly decreased when rock quality designation (RQD) data, common information when bore hole data are logged, is available since it is highly correlated with both shear and compression wave velocities. The results are used to derive region-specific site amplification factors as a function of both Vs30 and site fundamental frequency and compared to those of the National Building Code of Canada (2015). The results of the study indicate that there are large uncertainties associated with these parameters due to variability in soil profiles, soil properties and input seismic ground motions. Average and confidence intervals for the mean and for predictions of amplification factors are calculated for each site class to quantify this uncertainty. Amplifications normalized relative to class C are obtained by accounting for the correlation between site class amplifications for given ground motions. Non-linearity in the analysis of equivalent linear 1-D site response is taken into account by introducing the non-linear G/Gmax and damping ratios curves. In this method, it is assumed that the shear strain compatible shear modulus and damping ratio values remains constant throughout the duration of the seismic excitation. This assumption is not fully applicable to a case when loose saturated soil profile undergo heavy shaking (PGA > 0.3 g). In this study, all simulations with input motion PGA >0.3 g have been performed by using the EL method instead of the NL method considering that cohesive soils (clay and silt) at Montreal sites are stiff and cohesionless soils (sand and gravel) are considerably dense. In addition, the field and laboratory data required to perform NL analyses are not currently available and may be investigated in future works.