Academic literature on the topic 'Topographic site effect'
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Journal articles on the topic "Topographic site effect":
1
Ashford, Scott A., Nicholas Sitar, John Lysmer, and Nan Deng. "Topographic effects on the seismic response of steep slopes." Bulletin of the Seismological Society of America 87, no. 3 (June 1, 1997): 701–9. http://dx.doi.org/10.1785/bssa0870030701.
Abstract:
Abstract A frequency-domain parametric study using generalized consistent transmitting boundaries has been performed to evaluate the significance of topographic effects on the seismic response of steep slopes. The results show that the peak amplification of motion at the crest of a slope occurs at a normalized frequency H/λ = 0.2, where H is the slope height and λ is the wavelength of the motion. The importance of the natural site frequency is illustrated by the analysis of a stepped layer over a half-space. It was found that the natural frequency of the region behind the crest can dominate the response, relative to the topographic effect, for the conditions studied. Moreover, the effect of topography can be handled separately from the amplification due to the natural frequency of the deposit behind the crest of the slope. This concept of separating the amplification caused by topography from that caused by the natural frequency is advantageous to the development of a simplified method to estimate topographic effects.
2
Veeraraghavan, Swetha, Justin L. Coleman, and Jacobo Bielak. "Simulation of site and topographic effects on ground motion in Los Alamos, NM mesas." Geophysical Journal International 220, no. 3 (December 12, 2019): 1504–20. http://dx.doi.org/10.1093/gji/ggz448.
Abstract:
SUMMARY Mesas, which consist of an elevated area of land with a flat top and steep cliffs at the sides, are one of the common geological formations present in the Los Alamos region. Previous research has shown that geological formations such as sedimentary canyons can amplify soil response during earthquakes. There have also been parametric studies to understand the response of an idealized and isolated mountain/canyon under inclined plane waves. In this study, a 2-D linear anelastic soil domain, with topography modelled after the Los Alamos region with many mesas and canyons, is considered to understand site-specific topographic effects in the presence of non-isolated topographical features. Various earthquake sources configurations ranging from point sources to finite faults with varying rupture length, dip angles and spatial slip distributions are considered. To isolate the effect of topography, three other soil domains—a homogeneous half-space, homogeneous half-space with mesas and canyons, and a computational domain with just the soil properties from the Los Alamos region on a flat soil domain is also considered. 2-D site-response analyses of these soil domains under earthquake excitation show that the free-field response of the soil can be amplified or de-amplified depending on the topography of the region and the location of the station relative to the fault. These studies also show that even relatively small mesas with height less than 100 m can significantly amplify the response (by a factor of 2 or more), which differ from the much smaller amplification factors (≤1.2) specified by standard building codes such as Eurocode-8 (2000) for topographical features with a similar slope. De-amplifications are also fairly common, especially close to the canyons. The results from this study agree qualitatively with those from the ambient vibration study conducted by Stolte et al. on a mesa from the Los Alamos region. Thus, such site-specific studies provide important insights into the variability of the topographic amplification factors within a region of interest. Such knowledge is important in the design of safety-related critical infrastructure located within that region.
3
Fan, Gang, Fei Cheng Liu, Rui Zhi Wen, and Jian Jing Zhang. "Research of Earthquake Topographic Effect." Applied Mechanics and Materials 501-504 (January 2014): 1566–72. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.1566.
Abstract:
In this paper, the influence of topography on ground-motion intensity parameter, response spectrum, peak ground acceleration (PGA) and the ratio of response spectrum were studied based on the measured data from large scale shaking table test and observation stations in XiShan park for Wenchuan earthquake. The results show that: in the EW direction, the height do not affect PGD, SMA, VSI and HI, while V_RMS decreases slightly at the middle of the slope, the other intensity parameters increase with the increase of height. In the EW direction, the height has no influence on PGD, V_RMS, SMA, SED, A_RMS, VSI and HI, while other parameters increase as the height increase. In the UD direction, the height has no influence on SMV, PGD, V_RMS, SMV, ASI, VSI and HI, while A_RMS decreases at the middle of the slope, and the other intensity parameters increase as the height increase. Ignoring the local topographic effect, the amplitude of response spectrum increases with the increase of height at the part of short period (T1s), the part of long period (T>1s) is not effected by height. The ground motion will be amplified by local canyon topography, and the influence of local topography is larger than height. The research carried out in paper will deepen the understanding of topographic effect. 0 Preface Earthquake often cause extensive rock slope failures and various types of mass movement in mountainous areas. Catastrophic seismically-induced landsides are among the Earths most powerful geomorphic events, causing sudden and dramatic changes to the landscape, creating high risks to both infrastructures and life, and reputedly causing large economic losses. Seismic waves interacting with topography lead to amplification and deamplification of resulting ground motion. In the western mountainous areas of China, the topography is extremely complex, many large hydropower stations were built in narrow valleys and many large bridge piers were built on valleys and hillsides, so the research about topographic effect is essential to the seismic design of large-scale projects. Topographic effect is always analyzed with following three approaches: motion observation, analytical analysis and numerical analysis. The motion observation is regarded as the most efficient and common approach [1]. Long time ago, the researchers found that the intensity of buildings built on local convex topography was abnormal, in order to reveal the reason of abnormal intensity, array stations were constructed specially to study the effect of local convex topography on ground motion, some observation data were obtained. Some L-7 type strong motion seismographs were installed at the crest and foot of Kagel and Josephine mountain, California, by Lawrence L. Davis and Lewis R. West, the 2 array stations had recorded several aftershocks record of SanFernando earthquake, which occurred on February 9, 1971[. Some L-7 type strong motion seismographs were also installed at the crest, hillside and foot of Butler mountain, Nevada, to record blasting vibration in test site. In 1984, in order to observe the topographic effect of rocky mountain, 8 observation stations were installed by B. E. Tucker, five stations were placed in two tunnels with different elevation, the other three were placed at the surface of outcropped rock [. After the 1989 Loma prieta earthquake, dense array stations of seven digital and triaxial seismographs were mounted on Robinwood Ridge, which is located at 7.3km northwest of epicenter, to analyze the reason of seriously damage on high-strength buildings and cracks of ground [4,. In China, a earthquake observation station was constructed in XiShan Park, ZiGong, SiChuan province in 2007, which recorded the main acceleration time history of WenChuan earthquake perfectly, the establishment of this station offers valuable data to researchers for exploring the local topographic effect on ground motion [6]. In 2010, a research was conducted by Wang Haiyun and Xie Lili with traditional spectral ratio method, some significant conclusions were drawn about the influence of topographic effect on ground motion [7]. In this paper, WenChuan seismic wave was analyzed in time and frequency domain to explore the influence of topography on ground-motion intensity parameters, response spectrum and spectrum characteristic.
4
Hamilton, Gordon S. "Topographic control of regional accumulation rate variability at South Pole and implications for ice-core interpretation." Annals of Glaciology 39 (2004): 214–18. http://dx.doi.org/10.3189/172756404781814050.
Abstract:
AbstractSnow-accumulation rates are known to be sensitive to local changes in ice-sheet surface slope because of the effect of katabatic winds. These topographic effects can be preserved in ice cores that are collected at non-ice-divide locations. The trajectory of an ice-core site at South Pole is reconstructed using measurements of ice-sheet motion to show that snow was probably deposited at places of different surface slope during the past 1000 years. Recent accumulation rates, derived from shallow firn cores, vary along this trajectory according to surface topography, so that on a relatively steep flank mean annual accumulation is ∼18% smaller than on a nearby topographic depression. These modern accumulation rates are used to reinterpret the cause of accumulation rate variability with time in the long ice-core record as an ice-dynamics effect and not a climate-change signal. The results highlight the importance of conducting ancillary ice-dynamics measurements as part of ice-coring programs so that topographic effects can be deconvolved from potential climate signals.
5
Katebi, Mohammad, Behrouz Gatmiri, and Pooneh Maghoul. "A Numerical Study on the Seismic Site Response of Rocky Valleys with Irregular Topographic Conditions." Journal of Multiscale Modelling 10, no. 04 (December 2019): 1850011. http://dx.doi.org/10.1142/s1756973718500117.
Abstract:
This paper investigates topographic effects of rocky valleys with irregular topographic conditions subjected to vertically propagating SV waves of Ricker type using a boundary element code. Valleys with two intersecting slopes, [Formula: see text] and [Formula: see text], are modelled in order to study their combined effects on ground motion. Presented in the form of pseudo-acceleration response spectra, results of this work can be extended to similar topographies. The main findings are: (i) [Formula: see text] (the first slope angle) and [Formula: see text] (L is the half width of the valley and [Formula: see text] is its corresponding height) have amplifying effects, and [Formula: see text] (the second slope angle) has de-amplifying effects on the site response. (ii) [Formula: see text] has a straight effect on intensifying the effects of both [Formula: see text] and [Formula: see text]. (iii) The combined effects of slope angles have been found to be important in modifying the response so more than a single slope should be considered for seismic analysis. (iv) Engineers should use the maximum amplification of 2.4 in case of valleys with the first and second slope angles below [Formula: see text].
6
Ashford, Scott A., and Nicholas Sitar. "Analysis of topographic amplification of inclined shear waves in a steep coastal bluff." Bulletin of the Seismological Society of America 87, no. 3 (June 1, 1997): 692–700. http://dx.doi.org/10.1785/bssa0870030692.
Abstract:
Abstract The effect of inclined shear waves on the seismic response of a steep bluff is analyzed using generalized consistent transmitting boundaries. The results of the frequency-domain analysis of a stepped half-space subjected to incident shear waves inclined from 0° to 30° show that the motion at the crest of the slope is amplified for waves traveling into the slope and attenuated for waves traveling away from the slope, as compared to the motion in the free field behind the crest of the slope. This amplification can be as much as twice that observed for vertically propagating waves. A time-domain analysis of bluffs at Seacliff State Beach, California, is used to estimate the effect of topography using realistic conditions, taking into account wave inclination and site effects. The analysis of the site shows that although topographic amplification does in fact nearly double the amplitude of the motion in some cases, this amplification is offset by reduced site amplification and by wave splitting at material interfaces. Thus, the actual peak acceleration occurring at the crest of the slope changes little with incident angle as compared to the amplification of the free-field motion and actually decreases in many cases. Though a more general study is recommended, these results suggest that wave orientation and inclination substantially increase topographic amplification; however, it may be adequate to only account for vertically propagating waves for site response and slope stability analyses where only the magnitude of acceleration is considered.
7
Kingdon, Robert, Petr Vaníček, and Marcelo Santos. "Modeling topographical density for geoid determinationThis article is one of a series of papers published in this Special Issue on the theme GEODESY." Canadian Journal of Earth Sciences 46, no. 8 (August 2009): 571–85. http://dx.doi.org/10.1139/e09-018.
Abstract:
In geoid computation, effects of real three-dimensional topographic masses on the Earth’s gravity field must be accurately quantified and, in the Stokes–Helmert scheme, replaced with effects of those masses condensed on the geoid. The most comprehensive modern schemes for evaluation of topographical effects account for terrain effects, use a spherical model of topography, and incorporate two-dimensionally varying models of topographical mass density. In this contribution, we employ a three-dimensionally varying model of topographical density. We use Newton’s integration to determine the direct topographical effect (DTE) on gravity and primary indirect topographical effect (PITE) on gravity potential. Lastly, we apply Stokes’ integration to calculate the DTE, PITE, and secondary indirect topographical effect (SITE) on geoidal height. We focus here on validation of our results and demonstration of our software’s capabilities. We present results for the simple geometrical shape of a disc under various rotations and for the anomalous density of lake waters. Effects on geoidal height for these simulations reach centimetre level, up to 2.2 cm in magnitude. For a simulation of the effects of neglected mass anomalies of the lakes, we find results reaching 0.8 cm in magnitude. We examine the behavior of our results as calculated using various step sizes for numerical integration and by comparing numerical results with analytical results for the specific case of a disc. These results suggest that the maximum percent error of our results is about 23.5% for the DTE on gravity and 7.6% for the PITE on gravity potential.
8
Dharmadasa, Vasana, Christophe Kinnard, and Michel Baraër. "Topographic and vegetation controls of the spatial distribution of snow depth in agro-forested environments by UAV lidar." Cryosphere 17, no. 3 (March 14, 2023): 1225–46. http://dx.doi.org/10.5194/tc-17-1225-2023.
Abstract:
Abstract. Accurate knowledge of snow depth distributions in forested regions is crucial for applications in hydrology and ecology. In such a context, understanding and assessing the effect of vegetation and topographic conditions on snow depth variability is required. In this study, the spatial distribution of snow depth in two agro-forested sites and one coniferous site in eastern Canada was analyzed for topographic and vegetation effects on snow accumulation. Spatially distributed snow depths were derived by unmanned aerial vehicle light detection and ranging (UAV lidar) surveys conducted in 2019 and 2020. Distinct patterns of snow accumulation and erosion in open areas (fields) versus adjacent forested areas were observed in lidar-derived snow depth maps at all sites. Omnidirectional semi-variogram analysis of snow depths showed the existence of a scale break distance of less than 10 m in the forested area at all three sites, whereas open areas showed comparatively larger scale break distances (i.e., 11–14 m). The effect of vegetation and topographic variables on the spatial variability in snow depths at each site was investigated with random forest models. Results show that the underlying topography and the wind redistribution of snow along forest edges govern the snow depth variability at agro-forested sites, while forest structure variability dominates snow depth variability in the coniferous environment. These results highlight the importance of including and better representing these processes in physically based models for accurate estimates of snowpack dynamics.
9
Baron, Julie, Ilaria Primofiore, Peter Klin, Giovanna Vessia, and Giovanna Laurenzano. "Investigation of topographic site effects using 3D waveform modelling: amplification, polarization and torsional motions in the case study of Arquata del Tronto (Italy)." Bulletin of Earthquake Engineering 20, no. 2 (December 3, 2021): 677–710. http://dx.doi.org/10.1007/s10518-021-01270-2.
Abstract:
AbstractThe combined effect of topography and near-surface heterogeneities on the seismic response is hardly predictable and may lead to an aggravation of the ground motion. We apply physics-based numerical simulations of 3D seismic wave propagation to highlight these effects in the case study of Arquata del Tronto, a municipality in the Apennines that includes a historical village on a hill and a hamlet on the flat terrain of an alluvial basin. The two hamlets suffered different damage during the 2016 seismic sequence in Central Italy. We analyze the linear visco-elastic seismic response for vertically incident plane waves in terms of spectral amplification, polarization and induced torsional motion within the frequency band 1–8 Hz over a 1 km2 square area, with spatial resolution 25 m. To discern the effects of topography from those of the sub-surface structure we iterate the numerical simulations for three different versions of the sub-surface model: one homogeneous, one with a surficial weathering layer and a soil basin and one with a complex internal setting. The numerical results confirm the correlation between topographic curvature and amplification and support a correlation between the induced torsional motion and the topographic slope. On the other hand we find that polarization does not necessarily imply ground motion amplification. In the frequency band above 4 Hz the topography-related effects are mainly aggravated by the presence of the weathering layer, even though they do not exceed the soil-related effects in the flat-topography basin. The geological setting below the weathering layer plays a recognizable role in the topography-related site response only for frequencies below 4 Hz.
10
Hoch, Sebastian W., and C. David Whiteman. "Topographic Effects on the Surface Radiation Balance in and around Arizona’s Meteor Crater." Journal of Applied Meteorology and Climatology 49, no. 6 (June 1, 2010): 1114–28. http://dx.doi.org/10.1175/2010jamc2353.1.
Abstract:
Abstract The individual components of the slope-parallel surface radiation balance were measured in and around Arizona’s Meteor Crater to investigate the effects of topography on the radiation balance. The crater basin has a diameter of 1.2 km and a depth of 170 m. The observations cover the crater floor, the crater rim, four sites on the inner sidewalls on an east–west transect, and two sites outside the crater. Interpretation of the role of topography on radiation differences among the sites on a representative clear day is facilitated by the unique symmetric crater topography. The shortwave radiation balance was affected by the topographic effects of terrain exposure, terrain shading, and terrain reflections, and by surface albedo variations. Terrain exposure caused a site on the steeper upper eastern sidewall of the crater to receive 6% more daily integrated shortwave energy than a site on the lower part of the same slope. Terrain shading had a larger effect on the lower slopes than on the upper slopes. At the lower western slope site the daily total was reduced by 6%. Measurements indicate a diffuse radiation enhancement due to sidewall reflections. The longwave radiation balance was affected by counterradiation from the crater sidewalls and by reduced emissions due to the formation of a nighttime temperature inversion. The total nighttime longwave energy loss at the crater floor was 72% of the loss observed at the crater rim.
Dissertations / Theses on the topic "Topographic site effect":
1
Ma, Ning. "On the seismic response in a large deep-seated landslide in southwest Japan-with special focus on the topographic and geological effects-." Kyoto University, 2019. http://hdl.handle.net/2433/242901.
2
Bou, Nassif Aline. "Mouvements sismiques forts dans les régions montagneuses et mouvements de terrain induits." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALU039.
Abstract:
Après un séisme en zone de montagne, on observe fréquemment dans les zones proches de l'épicentre une grande variabilité dans la répartition spatiale des dommages, englobant à la fois les dommages structurels et les mouvements de terrain co-sismiques. Parmi d'autres facteurs, cette variabilité spatiale peut être en partie attribuée à l'amplification du mouvement sismique provoquée par la topographie. Bien que l'effet de la topographie ait été documenté depuis longtemps, il reste mal compris et est rarement considéré dans les normes de construction parasismique. Ma thèse est dédiée à la prédiction de l'amplification topographique du mouvement du sol à courte distance du séisme, et à l'étude de son impact sur les schémas de distribution spatiale des mouvements de terrain co-sismiques.Pour atteindre cet objectif, mon travail repose en premier lieu sur l'analyse par réseau neuronal de données synthétiques obtenues précédemment à partir de simulations 3D en différences finies de la propagation des ondes sismiques. Cette analyse vise à dériver un estimateur physique des effets de site topographique dans les zones proches de la source sismique. Ce proxy, que j’appelle i-FSC (illuminated Frequency Scaled Curvature), dépend de la longueur d'onde S, de la courbure de la surface topographique et d'un nouveau paramètre appelé « angle d'éclairage sismique normalisé », qui permet de quantifier l'exposition des pentes au champ d'onde sismique incident. Cet outil simple ne nécessite pas de ressources informatiques élevées ; il utilise seulement une carte numérique d'élévation de la surface et la position de la source sismique pour prédire les facteurs d'amplification en tout point de la surface topographique. Le proxy i-FSC permet d'explorer les variabilités dans l'amplification topographique des sites, causée par des sources sismiques proches. Cette avancée dans la prédiction de l'amplification topographique est particulièrement significative, car les zones les plus proches de la faille sont généralement les plus touchées pendant les séismes.Dans un second lieu, le proxy i-FSC est utilisé pour étudier la corrélation potentielle entre l'amplification topographique du mouvement sismique et la distribution spatiale des mouvements de terrain induits par des séismes tels que le séisme de Gorkha de 2015 (MW 7.8), le séisme de Kumamoto de 2016 (MW 7.1) et le séisme de Kaikōura de 2016 (MW 7.8). Les résultats montrent que les mouvements de terrain ont tendance à se localiser dans les zones amplifiées. Différents facteurs influençant le déclenchement des mouvements de terrain co-sismiques à différentes fréquences ont été identifiés. Aux basses fréquences, les mouvements de terrain ont tendance à se concentrer sur les pentes orientées en sens opposé à la source sismique (ayant des angles d'éclairage sismique plus élevés). À petite échelle spatiale, les localisations des mouvements de terrain correspondent aux zones d'amplification topographique à hautes fréquences, qui sont contrôlées par la courbure topographique. De plus, les mouvements de terrain ont tendance à se concentrer aux interfaces entre les pentes éclairées et non éclairées, ce qui peut indiquer des zones où la déformation de la pente est plus importante. Les résultats mettent également en évidence l'importance fondamentale de prendre en compte l'effet de l'amplification topographique, simplement dérivé par le proxy i-FSC, en conjonction avec d'autres facteurs classiques tels que la raideur des pentes, pour une meilleure compréhension des mécanismes complexes qui régissent la distribution spatiale des mouvements de terrain co-sismiques aux échelles locales et régionales.Les résultats de cette étude revêtent une grande importance, car ils pourraient orienter des recherches futures visant à élaborer des stratégies plus efficaces d'évaluation et de réduction des risques dans les régions montagneusesDuring an earthquake, a high degree of variability in damage distribution, encompassing both structural damage and co-seismic landslides, is commonly observed in mountainous regions near the seismic source. Among other factors, this spatial variability can be partly attributed to the amplification of seismic waves caused by surface topography. While this effect has long been documented, it remains poorly understood and is rarely incorporated into building specification codes. My thesis is dedicated to predicting the amplification of ground motion caused by surface topography in close distances to an earthquake, and studying its potential impact on co-seismic landslides distribution patterns.To achieve this goal, my work initially relies on neural network analysis of previously-available synthetic data obtained from 3D finite-differences simulations of seismic wave propagation. This analysis aims to derive a physics-based estimator of topographic site effects in close distances to the source. This proxy, which I refer to as the i-FSC proxy (illuminated Frequency Scaled Curvature), depends on the S-wavelength, the curvature of the topographic surface, and a new parameter called the “normalized seismic illumination angle” which quantifies the slope's exposure to the incoming wavefield. This user-friendly tool does not require high computational resources; it only uses a digital elevation map and the position of the seismic source to predict amplification factors at any point of the surface topography. The i-FSC allows exploring the variations in topographic amplification influenced by nearby seismic sources. This advancement is particularly significant as the areas closest to the fault are typically the ones most severely affected during earthquakes.Subsequently, the i-FSC proxy is employed to investigate the correlation between ground motion amplification and the spatial distribution of earthquake-induced landslides triggered by events such as the 2015 Gorkha earthquake (MW 7.8), the 2016 Kumamoto earthquake (MW 7.1), and the 2016 Kaikōura earthquake (MW 7.8). The results indicate that co-seismic landslides tend to be localized in amplified areas. Different controls on the landslide triggering at different frequencies have been identified. At lower frequencies, landslides tend to concentrate on slopes facing away from the seismic source (with higher seismic illumination angles). At smaller scales, the location of landslides mimics the amplification maps at higher frequencies, which are primarily influenced by surface topography curvature. Furthermore, landslides appear to also cluster at the interfaces between illuminated and non-illuminated slopes, which may indicate areas where slope deformation is the greatest. The results also highlight the crucial importance of considering the effect of topographic amplification, simply derived by the i-FSC proxy, together with other classic factors such as slope steepness, for a better understanding of the complex mechanisms governing the spatial distribution of earthquake-induced landslides at local and regional scales.The results of this study hold significant importance, as they could guide future research efforts aimed at developing more effective risk assessment and mitigation strategies in mountainous regions
3
Panzera, Francesco. "Approaches to earthquake scenarios validation using seismic site response." Doctoral thesis, Università di Catania, 2012. http://hdl.handle.net/10761/1084.
Abstract:
A seismic hazard assessment was carried out for the Catania and Siracusa towns providing a comprehensive re-examination and re-processing of all the available seismic data. The site approach and the seismotectonic one were used and compared. The hazard assessment, using both methods, was performed following a logic-tree approach in order to consider and reduce the epistemic uncertainties. The combined use and comparison of these approaches is recommended since it allows to verify the robustness of the hazard estimates and allowed us to obtain useful elements to define the seismic hazard in Catania and Siracusa.
Experimental data and numerical modeling were used to study the effect of local geology on the seismic response in the Catania area. Available boreholes data and elastic parameters were used to reconstruct a geotechnical model in order to perform 1D numerical modeling. Seismic urban scenarios were simulated considering destructive (Mw=7.0), strong (Mw=6.2) and moderate (Mw=5.7) earthquakes. PGA and spectral acceleration at different periods were obtained in the urban area through the equivalent linear numerical code EERA, and contour maps of different levels of shaking were drawn. Standard and horizontal-to-vertical spectral ratios were achieved making use of a dataset of 172 seismic events recorded at ten stations located on the main outcropping lithotypes. Spectral ratios inferred from earthquake data were compared with theoretical transfer functions. Both experimental and numerical results confirm the role of the geologic and morphologic setting of Catania.
A study aimed to investigate on the dynamic properties of main lithotypes outcropping in the Siracusa area and their relationships with the local seismic response was performed. Non-invasive seismic prospecting techniques using the vertical component of surface waves (MASW and ReMi) were adopted, as well as ambient noise measurements, processed through the Nakamura technique. Moreover, a cluster analysis was performed to subdivide into homogeneous groups the experimentally obtained noise spectral ratios. Results pointed out that the use of combined different methods provides a more robust way to characterized the investigated soils and to reduce the problems linked to the non-uniqueness of solutions during the interpretation of geophysical data.
The role of local geology and topography on the site response of a small hill, located in the northern part of Catania, was investigated. Ambient noise and earthquake data were processed through standard and horizontal-to-vertical spectral ratios. Directional effects were also investigated by computing the spectral ratios after rotating the horizontal components of motion and performing polarization analysis. Results of noise and earthquakes analysis, although show significant differences in amplitude, are comparable in frequency, especially in the sedimentary terrains. Pronounced directional effects are mostly observed on the slopes rather than at the hill top. Our findings appear linked to the complex wavefield generated by the lithologic heterogeneities existing in the area which seem to have a stronger influence with respect to the simple topographic effect.
Seismic noise recorded by mobile stations in the Ortigia peninsula (downtown Siracusa) was analyzed through H/V spectral ratios, to investigate local site effects. Moreover, shear wave velocities were investigated through non-invasive techniques (MASW and ReMi) in order to assess the theoretical resonant frequency of the hill. Experimental results coming out from the spectral ratios show peaks in the frequency range 1.0-3.0 Hz which are consistent with the theoretical resonance frequency at Ortigia. The H/V azimuthal spectral analysis shows a clearly predominant E-W directional effect, transversal to the main axis of the peninsula, which is also confirmed by the polarization analysis in the time domain.
4
Zhang, Zezhong. "Stabilité dynamique des versants et effets de site d’origine géomorphologique : simulations numériques et rétro-analyses." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM074/document.
Abstract:
Dans cette thèse, des simulations numériques ont d'abord été effectuées avec le logiciel FLAC (Itasca) sur un modèle de pente élastique linéaire homogène pour caractériser l'amplification de l'accélération le long de la surface située le long et à l’arrière de la crête d'une pente, et évaluer ainsi l'effet de la topographie sur l'amplification de l'accélération. L'interaction entre la fréquence du signal sismique appliqué à la base du modèle et l'angle et la hauteur de la pente a été particulièrement étudiée. Il a été constaté que le facteur d’amplification de l’accélération varie de manière significative avec l’angle de et la hauteur de la pente, la fréquence et la durée (nombre de cycle) du signal. De plus, l'amplification du mouvement du sol due à la topographie de la pente est influencée de manière significative par l'effet de couplage complexe entre les ondes incidentes et les ondes réfléchies sur la topographie, et qu’elle est fortement contrôlée par le rapport entre la longueur d'onde du signal incident et la hauteur de la pente.Les simulations numériques sont basées sur une étude géotechnique et une modélisation géomécanique nécessitant de valider les résultats par des comparaisons entre les résultats de modélisations et les données provenant des observations sur le terrain. L’analyse des domaines de fréquence, telle que la densité spectrale et la réponse en fréquence, est un moyen performant pour comprendre les caractéristiques des processus et les divers phénomènes qui ne peuvent pas être expliqués dans le domaine temporel. À cette fin, une étude de la crête du parc Xishan à Zigong au Sichuan en Chine a été réalisée. Les amplifications du site associées au mouvement du sol produit par le séisme de Wenchuan en 2008 ont été évaluées à l'aide de la technique du rapport spectral standard (SSR) et de la méthode d'accélération quadratique moyenne (arms) dans le domaine temporel. Une analyse numérique à 2D utilisant la méthode des différences finies au moyen du logiciel FLAC (Itasca) a été ensuite mise en œuvre et les résultats ont été comparés aux mesures de terrain. Les pics “simulés” des amplifications spectrales sont toujours inférieurs à ceux dérivés des enregistrements de terrain. L'effet d'atténuation important sur le mouvement d'entrée pour les hautes fréquences met en évidence le fait qu'un rapport d'amortissement du signal ne représente pas correctement la dissipation d'énergie dans les simulations numériques. Des amplifications significatives se sont produites à des fréquences élevées (> 10 Hz) et sont considérées comme résultant de conditions locales spécifiques telles que la fracturation des roches et les marches de faîtage; ils ne se produisent donc pas nécessairement au sommet de la colline.Enfin, des études paramétriques ont été réalisées avec des modèles élastiques en termes de diverses géométries de pente 2D et de couches géologiques de subsurface pour caractériser les amplifications du mouvement du sol. L’analyse paramétrique a pour but de comprendre le rôle joué par ces couches de surface, l’angle de la pente et la hauteur de la pente sur l’amplification du mouvement du sol,et donc d’évaluer si l’amplification du site peut être responsable du déclenchement du glissement de terrain. Ensuite, l'analyse dynamique sur des modèles de pente pour différentes magnitudes a été effectuée et une rupture de pente basée sur le déplacement a été créée pour évaluer la stabilité de la pente du site de Las Colinas au Salvador. Les résultats numériques ont clairement montré que les effets de site peuvent avoir induit d'importantes amplifications du mouvement du sol qui ont contribué à déclencher des glissements de terrainIn this research work, numerical simulations using the finite difference FLAC software (Itasca) were first conducted with a homogeneous linear elastic slope model in order to characterize the acceleration amplification along the slope surface and behind the slope crest, and then to evaluate the topographic effect on the acceleration amplification. The interaction between the frequency of the seismic input motion applied at the base of the model with the slope angle and height has been deeply investigated. It was found that significant changes in the acceleration amplification factor result from variations in the slope angle and height as well as the signal frequency and duration. In addition, it has been shown that the ground motion amplification due to slope topography result from complex coupling effects between the input waves and the reflected waves on the topographic features and is highly controlled by the ratio between the wavelength of the input signal and the slope height.Numerical simulations are based on geotechnical investigations and geotechnical modeling, and it is necessary to validate the results through comparisons between modeling results and field observations. Frequency domain analysis such as spectral density and frequency response are an effective way to understand process characteristics and the various phenomena that cannot be explained in the time domain. For this purpose, a case study at Xishan Park ridge in Zigong in China has been studied. Site amplifications associated with the ground motion produced by the 2008 Wenchuan earthquake have been evaluated using the Standard Spectral Ratio (SSR) technique and root-mean-square acceleration (arms) method in time domain. 2D numerical analysis using finite difference method using the FLAC software (Itasca) has been then performed and results have been compared with monitoring data. The “simulated” peaks of the spectral amplifications are always lower than those derived from the field records. The strong attenuation of input motion at high frequencies highlights the shortcoming that a signal damping ratio does not adequately represent the energy dissipation in numerical simulations. Significant amplifications occurred at high frequencies (>10 Hz) and are considered to result from local specific conditions such as rock fracturing and ridge steps; thus they do not necessarily occur at the top of the hill. Finally, parametric studies were performed with elastic models in terms of various 2D slope geometries and geological layers to characterize the ground motion amplifications. The purpose of the parametric analysis is to understand the role of the geological layer, slope angle and slope height on the ground motion amplification, and thus to estimate if site amplifications could be responsible for the triggering of landslide. Then, the dynamic analysis on the slope model for different seismic magnitudes was performed and a slope failure based on displacement was created to evaluate the Las Colinas slope stability in Salvador. The numerical results clearly showed that site effects can have induced significant ground motion amplifications that contributed to trigger landslides
5
Nguyen, Hieu Toan. "Évaluation des effets de site topographiques dans les pentes soumises à des sollicitations dynamiques par simulations numériques." Electronic Thesis or Diss., Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0074.
Abstract:
Les séismes sont connus comme des catastrophes naturelles destructrices et meurtrières. Particulièrement dans les régions montagneuses, les effets des séismes sont encore beaucoup plus aggravés à cause des effets de site topographiques. La présence d'une pente est à l'origine d'une amplification du signal sismique notamment dans le voisinage de la crête. De nombreux séismes anciens tels que le séisme de Lambesc (1909, Ms=6.2) qui a conduit à la destruction du village de Rognes (Bouches-du-Rhône, France), ou plus récemment le séisme d'Athènes en Grèce (1999, Ms=5.9) qui a endommagé la ville d'Adames ainsi que les séismes de Chichi à Taiwan (1999, Mw=7.6), du Salvador (2001, Mw=7.6) et du Sichuan (2008, Mw=7.9) responsables de très nombreux glissements de terrain particulièrement catastrophiques sont des exemples représentatifs. Les investigations post-sismiques ont montré une contribution importante des effets de site topographiques au bilan des dommages humains et matériels. Dans le but d'améliorer les connaissances de ce phénomène, de nombreuses simulations numériques ont été réalisées sur des modèles de versant isolés en utilisant le logiciel FLAC 2D (Itasca). Les résultats obtenus ont été analysés en considérant plusieurs critères comme les facteurs d'amplification, les surfaces et les dimensions des zones d'amplification ainsi que la distribution spatiale de ces zones dans le massif de versant. Des études paramétriques ont permis de mettre en évidence le rôle principal de la fréquence adimensionnelle, rapport de la hauteur du versant à la longueur d'onde du signal sismique, dans l'évaluation des effets de site topographiques. Ces résultats montrent également que la pente est le deuxième paramètre important, suivie du coefficient de Poisson et de la géométrie de la crête et du pied de la pente.Ces résultats numériques ont également permis de définir des relations empiriques, nommées ANS, qui permettent d'estimer les effets de site topographiques selon les différents critères d'interprétation. Ces formules sont adaptées pour les signaux sismiques avec une bande de fréquences prédominantes relativement étroite. Pour les autres cas, la Méthode de Décomposition des ondes (MD) a été développé dans ce travail. Cette méthode est basée sur la décomposition du signal complexe multi-fréquentiel en plusieurs ondes mono-fréquentielles par transformée de Fourier. L'effet du signal complexe est alors évalué en faisant une combinaison des effets individuels de chaque onde élémentaire. Ces approches développées dans ce travail (ANS et MD) permettent d'évaluer les effets de site topographiques, en tenant compte de plusieurs paramètres géomorphologiques et sismiques du massif de versant ainsi que du contenu fréquentiel du signal sismique, sans avoir recours à des simulations numériquesEarthquakes are known as destructive and murderous natural catastrophe. Particularly in the mountainous regions, the effects of earthquakes are still much aggravated due to the topographic site effects. The presence of a slope causes an amplification of the seismic signal, particularly in the vicinity of the crest. Numerous earthquakes in the past such as the 1909 Lambesc earthquake (Ms=6.2) which led to the destruction of the Rognes village (Bouches-du-Rhône, France), or more recently the 1999 Athens, Greece earthquake (Ms=5.9) which damaged the Adames city as well as the 1999 Chichi, Taiwan earthquake (MW=7.6), the 2001 El Salvador earthquake (MW=7.6) and the 2008 Sichuan earthquake (MW=7.9) responsible for numerous catastrophic landslides are representative examples. Post-seismic investigations demonstrated a significant contribution of topographic site effects on the human and material damage assessment.In order to improve the knowledge of this phenomenon, numerous numerical simulations were performed on the step-like slope models by using the FLAC 2D software (Itasca). The obtained results were analyzed by considering various criteria such as amplification factors, dimensions and area of amplification zones as well as spatial distribution of these zones inside the slope mass. The parametric analyses allow underlining the principal role of the dimensionless frequency, ratio of the slope height to the wavelength of the seismic signal, in the evaluation of topographic site effects. These results also show that the slope angle is the second important parameter, followed by the Poisson's ratio and the geometry of the crest and of the toe of slope.These numerical results allow pointing out empirical equations, called ANS, which can be used to estimate the topographic site effects according to different interpretation criteria. These formulas are suitable for seismic signals with a relatively narrow band of predominant frequencies. For other cases, the method concerning decomposition of seismic incident wave (MD) was developed in this work. This method is based on the decomposition of the complex multi-frequency seismic signal into multiple mono-frequency waves by using Fourier transform. The effect of the complex signal is then evaluated through a combination of the effects of elementary waves. The approaches developed in this work (ANS and MD) allow evaluating the topographic site effects, by taking into account geomorphologic and seismic parameters of the slope as well as the frequency content of the seismic signal, without recourse to numerical simulations
6
Nguyen, Hieu Toan. "Évaluation des effets de site topographiques dans les pentes soumises à des sollicitations dynamiques par simulations numériques." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0074/document.
Abstract:
Les séismes sont connus comme des catastrophes naturelles destructrices et meurtrières. Particulièrement dans les régions montagneuses, les effets des séismes sont encore beaucoup plus aggravés à cause des effets de site topographiques. La présence d'une pente est à l'origine d'une amplification du signal sismique notamment dans le voisinage de la crête. De nombreux séismes anciens tels que le séisme de Lambesc (1909, Ms=6.2) qui a conduit à la destruction du village de Rognes (Bouches-du-Rhône, France), ou plus récemment le séisme d'Athènes en Grèce (1999, Ms=5.9) qui a endommagé la ville d'Adames ainsi que les séismes de Chichi à Taiwan (1999, Mw=7.6), du Salvador (2001, Mw=7.6) et du Sichuan (2008, Mw=7.9) responsables de très nombreux glissements de terrain particulièrement catastrophiques sont des exemples représentatifs. Les investigations post-sismiques ont montré une contribution importante des effets de site topographiques au bilan des dommages humains et matériels. Dans le but d'améliorer les connaissances de ce phénomène, de nombreuses simulations numériques ont été réalisées sur des modèles de versant isolés en utilisant le logiciel FLAC 2D (Itasca). Les résultats obtenus ont été analysés en considérant plusieurs critères comme les facteurs d'amplification, les surfaces et les dimensions des zones d'amplification ainsi que la distribution spatiale de ces zones dans le massif de versant. Des études paramétriques ont permis de mettre en évidence le rôle principal de la fréquence adimensionnelle, rapport de la hauteur du versant à la longueur d'onde du signal sismique, dans l'évaluation des effets de site topographiques. Ces résultats montrent également que la pente est le deuxième paramètre important, suivie du coefficient de Poisson et de la géométrie de la crête et du pied de la pente.Ces résultats numériques ont également permis de définir des relations empiriques, nommées ANS, qui permettent d'estimer les effets de site topographiques selon les différents critères d'interprétation. Ces formules sont adaptées pour les signaux sismiques avec une bande de fréquences prédominantes relativement étroite. Pour les autres cas, la Méthode de Décomposition des ondes (MD) a été développé dans ce travail. Cette méthode est basée sur la décomposition du signal complexe multi-fréquentiel en plusieurs ondes mono-fréquentielles par transformée de Fourier. L'effet du signal complexe est alors évalué en faisant une combinaison des effets individuels de chaque onde élémentaire. Ces approches développées dans ce travail (ANS et MD) permettent d'évaluer les effets de site topographiques, en tenant compte de plusieurs paramètres géomorphologiques et sismiques du massif de versant ainsi que du contenu fréquentiel du signal sismique, sans avoir recours à des simulations numériquesEarthquakes are known as destructive and murderous natural catastrophe. Particularly in the mountainous regions, the effects of earthquakes are still much aggravated due to the topographic site effects. The presence of a slope causes an amplification of the seismic signal, particularly in the vicinity of the crest. Numerous earthquakes in the past such as the 1909 Lambesc earthquake (Ms=6.2) which led to the destruction of the Rognes village (Bouches-du-Rhône, France), or more recently the 1999 Athens, Greece earthquake (Ms=5.9) which damaged the Adames city as well as the 1999 Chichi, Taiwan earthquake (MW=7.6), the 2001 El Salvador earthquake (MW=7.6) and the 2008 Sichuan earthquake (MW=7.9) responsible for numerous catastrophic landslides are representative examples. Post-seismic investigations demonstrated a significant contribution of topographic site effects on the human and material damage assessment.In order to improve the knowledge of this phenomenon, numerous numerical simulations were performed on the step-like slope models by using the FLAC 2D software (Itasca). The obtained results were analyzed by considering various criteria such as amplification factors, dimensions and area of amplification zones as well as spatial distribution of these zones inside the slope mass. The parametric analyses allow underlining the principal role of the dimensionless frequency, ratio of the slope height to the wavelength of the seismic signal, in the evaluation of topographic site effects. These results also show that the slope angle is the second important parameter, followed by the Poisson's ratio and the geometry of the crest and of the toe of slope.These numerical results allow pointing out empirical equations, called ANS, which can be used to estimate the topographic site effects according to different interpretation criteria. These formulas are suitable for seismic signals with a relatively narrow band of predominant frequencies. For other cases, the method concerning decomposition of seismic incident wave (MD) was developed in this work. This method is based on the decomposition of the complex multi-frequency seismic signal into multiple mono-frequency waves by using Fourier transform. The effect of the complex signal is then evaluated through a combination of the effects of elementary waves. The approaches developed in this work (ANS and MD) allow evaluating the topographic site effects, by taking into account geomorphologic and seismic parameters of the slope as well as the frequency content of the seismic signal, without recourse to numerical simulations
7
Zhang, Zezhong. "Stabilité dynamique des versants et effets de site d’origine géomorphologique : simulations numériques et rétro-analyses." Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM074.
Abstract:
Dans cette thèse, des simulations numériques ont d'abord été effectuées avec le logiciel FLAC (Itasca) sur un modèle de pente élastique linéaire homogène pour caractériser l'amplification de l'accélération le long de la surface située le long et à l’arrière de la crête d'une pente, et évaluer ainsi l'effet de la topographie sur l'amplification de l'accélération. L'interaction entre la fréquence du signal sismique appliqué à la base du modèle et l'angle et la hauteur de la pente a été particulièrement étudiée. Il a été constaté que le facteur d’amplification de l’accélération varie de manière significative avec l’angle de et la hauteur de la pente, la fréquence et la durée (nombre de cycle) du signal. De plus, l'amplification du mouvement du sol due à la topographie de la pente est influencée de manière significative par l'effet de couplage complexe entre les ondes incidentes et les ondes réfléchies sur la topographie, et qu’elle est fortement contrôlée par le rapport entre la longueur d'onde du signal incident et la hauteur de la pente.Les simulations numériques sont basées sur une étude géotechnique et une modélisation géomécanique nécessitant de valider les résultats par des comparaisons entre les résultats de modélisations et les données provenant des observations sur le terrain. L’analyse des domaines de fréquence, telle que la densité spectrale et la réponse en fréquence, est un moyen performant pour comprendre les caractéristiques des processus et les divers phénomènes qui ne peuvent pas être expliqués dans le domaine temporel. À cette fin, une étude de la crête du parc Xishan à Zigong au Sichuan en Chine a été réalisée. Les amplifications du site associées au mouvement du sol produit par le séisme de Wenchuan en 2008 ont été évaluées à l'aide de la technique du rapport spectral standard (SSR) et de la méthode d'accélération quadratique moyenne (arms) dans le domaine temporel. Une analyse numérique à 2D utilisant la méthode des différences finies au moyen du logiciel FLAC (Itasca) a été ensuite mise en œuvre et les résultats ont été comparés aux mesures de terrain. Les pics “simulés” des amplifications spectrales sont toujours inférieurs à ceux dérivés des enregistrements de terrain. L'effet d'atténuation important sur le mouvement d'entrée pour les hautes fréquences met en évidence le fait qu'un rapport d'amortissement du signal ne représente pas correctement la dissipation d'énergie dans les simulations numériques. Des amplifications significatives se sont produites à des fréquences élevées (> 10 Hz) et sont considérées comme résultant de conditions locales spécifiques telles que la fracturation des roches et les marches de faîtage; ils ne se produisent donc pas nécessairement au sommet de la colline.Enfin, des études paramétriques ont été réalisées avec des modèles élastiques en termes de diverses géométries de pente 2D et de couches géologiques de subsurface pour caractériser les amplifications du mouvement du sol. L’analyse paramétrique a pour but de comprendre le rôle joué par ces couches de surface, l’angle de la pente et la hauteur de la pente sur l’amplification du mouvement du sol,et donc d’évaluer si l’amplification du site peut être responsable du déclenchement du glissement de terrain. Ensuite, l'analyse dynamique sur des modèles de pente pour différentes magnitudes a été effectuée et une rupture de pente basée sur le déplacement a été créée pour évaluer la stabilité de la pente du site de Las Colinas au Salvador. Les résultats numériques ont clairement montré que les effets de site peuvent avoir induit d'importantes amplifications du mouvement du sol qui ont contribué à déclencher des glissements de terrainIn this research work, numerical simulations using the finite difference FLAC software (Itasca) were first conducted with a homogeneous linear elastic slope model in order to characterize the acceleration amplification along the slope surface and behind the slope crest, and then to evaluate the topographic effect on the acceleration amplification. The interaction between the frequency of the seismic input motion applied at the base of the model with the slope angle and height has been deeply investigated. It was found that significant changes in the acceleration amplification factor result from variations in the slope angle and height as well as the signal frequency and duration. In addition, it has been shown that the ground motion amplification due to slope topography result from complex coupling effects between the input waves and the reflected waves on the topographic features and is highly controlled by the ratio between the wavelength of the input signal and the slope height.Numerical simulations are based on geotechnical investigations and geotechnical modeling, and it is necessary to validate the results through comparisons between modeling results and field observations. Frequency domain analysis such as spectral density and frequency response are an effective way to understand process characteristics and the various phenomena that cannot be explained in the time domain. For this purpose, a case study at Xishan Park ridge in Zigong in China has been studied. Site amplifications associated with the ground motion produced by the 2008 Wenchuan earthquake have been evaluated using the Standard Spectral Ratio (SSR) technique and root-mean-square acceleration (arms) method in time domain. 2D numerical analysis using finite difference method using the FLAC software (Itasca) has been then performed and results have been compared with monitoring data. The “simulated” peaks of the spectral amplifications are always lower than those derived from the field records. The strong attenuation of input motion at high frequencies highlights the shortcoming that a signal damping ratio does not adequately represent the energy dissipation in numerical simulations. Significant amplifications occurred at high frequencies (>10 Hz) and are considered to result from local specific conditions such as rock fracturing and ridge steps; thus they do not necessarily occur at the top of the hill. Finally, parametric studies were performed with elastic models in terms of various 2D slope geometries and geological layers to characterize the ground motion amplifications. The purpose of the parametric analysis is to understand the role of the geological layer, slope angle and slope height on the ground motion amplification, and thus to estimate if site amplifications could be responsible for the triggering of landslide. Then, the dynamic analysis on the slope model for different seismic magnitudes was performed and a slope failure based on displacement was created to evaluate the Las Colinas slope stability in Salvador. The numerical results clearly showed that site effects can have induced significant ground motion amplifications that contributed to trigger landslides
8
Kuehnert, Julian. "Simulation of High Frequency Seismic Waves generated by Rockfalls on Real Topography." Thesis, Université de Paris (2019-....), 2019. https://theses.md.univ-paris-diderot.fr/KUEHNERT_Julian_va2.pdf.
Abstract:
Les risques d'éboulements doivent être évalués et surveillés afin de prévenir les pertes de vies humaines et dommages aux infrastructures. A cet égard, il est important de créer des catalogues d'événements et de comprendre la dynamique des éboulements. Les ondes sismiques peuvent être utiles à cette fin, car elles transmettent des informations précieuses sur l'événement. Elles sont générées lorsque des éboulements touchent le sol et peuvent être utilisées pour détecter, classer et localiser des événements. Plus encore, on peut déduire des propriétés des éboulements telles que leur volumes et leur comportement dynamique. Cependant, les signaux sismiques hautes fréquences (>1Hz) sont mal compris. En effet, ils sont associés à des sources sismiques complexes qui sont réparties dans l'espace et peuvent varier rapidement dans le temps. De plus, les ondes sismiques hautes fréquences sont susceptibles d'être diffusées et diffractées en raison des interactions avec les hétérogénéités du sol ou la topographie de surface. Cette thèse franchit une étape importante dans la compréhension des signaux sismiques hautes fré-quences des éboulements en simulant la propagation des ondes sismiques en utilisant la méthode des éléments spectraux (SEM) avec des profils de vitesse réalistes et des topographies de surface 3D. L'influence de la topographie sur le champ des ondes sismiques est étudiée. On constate que l'ampli-fication induite par la topographie est sensiblement différente entre les sources situées en profondeurs et celles situées en surface. En effet, les ondes de surface générées par des sources peu profondes sont exposées à une diffusion et à une diffraction constantes lorsqu'elles se déplacent le long de la surface. La désintégration de l'énergie le long de la surface est étudiée pour différents modèles de vitesse et des équations sont dérivées pour calculer rétroactivement l'énergie sismique totale rayonnée par la source. Ceci est intéressant du fait du lien entre l'énergie sismique et le volume d'éboulement. Afin de tenir compte des effets topographiques, il est proposé un facteur de correction qui peut être introduit dans le calcul de l'énergie. Les signaux sismiques générés par les éboulements du cratère Dolomieu du Piton de la Fournaise, à La Réunion, sont analysés. Les sismogrammes synthétiques sont utilisés pour identifier et interpréter les signaux observés qui sont générés par des impacts uniques. L'influence de la topographie sur les formes d'onde est démontrée et la sensibilité avec l'emplacement et la direction de la source est évaluée. Les caractéristiques du signal telles que les amplitudes et le contenu fréquentiel sont expliquées sur la base de la théorie du contact de Hertz. De plus, les rapports spectraux entre stations, calculés à partir des signaux sismiques d'éboulement, sont considérés comme caractéristiques de la position de la source. La comparaison avec les rapports spectraux simulés suggère qu'ils sont dominés par la propagation le long de la topographie plutôt que par le mécanisme de la source. Sur la base de ces résultats, une méthode est proposée pour la localisation des éboulements à l'aide de rapports énergétiques simulés entre stations. La méthode est appliquée pour localiser les éboulements dans le cratère de Dolomieu. La mise en œuvre de la méthode implique une fenêtre temporelle glissante qui permet une application simple sur des signaux sismiques continus. L'accent est mis sur la capacité de la méthode à surveiller l'activité des éboulements en temps réelRockfall hazard has to be evaluated and monitored in order to prevent loss of life and infrastructure. In this regard it is important to create event catalogs and understand rockfall dynamics. Seismic waves can help for this purpose as they carry valuable information of the event. They are generated when rockfalls impact the ground and can be used to detect, classify and locate events. Beyond that, rockfall properties such as their volume and their dynamic behavior can be inferred. Yet, high frequency seismic signals (>1Hz) are poorly understood. This is because they are associated to complex seismic sources which are spatially distributed and can rapidly vary over time. On top of this, high frequency seismic waves are prone to be scattered and diffracted due to interactions with soil heterogeneities or surface topography. This thesis takes an important step forward to enhance understanding of high frequency rockfall seismic signals by simulating seismic wave propagation on domains with realistic velocity profiles and 3D surface topographies using the Spectral Element Method (SEM). The influence of the topography on the seismic wave field is investigated. It is found that topography induced amplification is substantially different between deep sources and sources located at the surface. This is because surface waves generated by shallow sources are exposed to constant scattering and diffraction when traveling along the surface. The energy decay along the surface is investigated for different velocity models and equations are derived to back-calculate the total seismic energy radiated by the source. This is of interest as the rockfall seismic energy is related to the rockfall volume. In order to account for topography effects, a correction factor is proposed which can be introduced in the energy calculation. Observed seismic signals generated by rockfall at Dolomieu crater on Piton de la Fournaise volcano, La Réunion, are analyzed. Synthetic seismograms are used to identify and interpret observed signals generated by single impacts. The influence of topography on the waveforms is demonstrated and the sensitivity on source location as well as source direction is evaluated. Signal characteristics such as amplitudes and frequency content are explained based on Hertz contact theory. Additionally, inter-station spectral ratios computed from rockfall seismic signals are shown to be characteristic of the source position. Comparison with simulated spectral ratios suggest that they are dominated by the propagation along the topography rather than the mechanism of the source. Based on these findings, a method is proposed for the localization of rockfalls using simulated inter-station energy ratios. The method is applied to localize rockfalls at Dolomieu crater. The implementation of the method involves a sliding time window which allows a straightforward application on continuous seismic signals. The potential of the method to monitor rockfall activity in real-time is emphasized
9
Pedersen, Helle Anette. "Étude de la diffraction tridimensionnelle des ondes sismiques dans des structures à géométrie bidimensionnelle : développement théorique et applications." Grenoble 1, 1994. http://www.theses.fr/1994GRE10212.
Abstract:
La diffraction tridimensionnelle (3d) des ondes sismiques par des structures a geometrie bidimensionnelle (2d) est etudiee par la methode indirecte d'elements de frontiere (ibem, pour indirect boundary element method). Les ondes incidentes peuvent arriver en dehors du plan 2d et, en consequence, la diffraction est 3d avec couplage de tous les types d'onde. Ce travail est divise en trois parties. La theorie de ibem et son extension aux problemes de diffraction 3d par des structures 2d sont presentees dans la premiere partie. La deuxieme est consacree a l'application de la methode pour l'etude de la diffraction et de l'amplification par des reliefs topographiques et des vallees sedimentaires. La derniere partie consiste en l'etude d'une suture lithospherique et en une simulation numerique de la diffraction des ondes de surface par cette suture. Les resultats majeurs de ce travail sont a la fois de nature theorique et pratique. Ibem s'avere etre une methode precise et rapide pour simuler la diffraction 3d par des structures 2d. Elle est numeriquement stable et permet le calcul du champ d'onde complet en prenant en compte le transfert d'energie entre differentes types d'ondes. Ibem semble ainsi etre un outil prometteur pour l'interpretation de donnees sismologiques. L'analyse de donnees ainsi que les simulations numeriques de la propagation d'ondes au travers de reliefs topographiques et de vallees sedimentaires montrent que: 1) les effets 3d sont importants, 2) l'amplification due aux reliefs topographiques est faible, et 3) des ondes diffractees sont emises du sommet des reliefs. Enfin, nous avons mis en evidence un changement rapide de la structure lithospherique sous la zone sorgenfrei-tornquist par analyse d'ondes de rayleigh de longue periode. La simulation numerique montre que les ondes de rayleigh incidentes sur une telle suture sont transmises ou reflechies sous la forme d'ondes de surface ou de volume
10
Delavaud, Elise. "Simulation numérique de la propagation d'ondes en milieu géologique complexe : application à l'évaluation de la réponse sismique du bassin de Caracas (Venezuela)." Paris, Institut de physique du globe, 2007. http://www.theses.fr/2007GLOB0010.
Abstract:
Ce travail de thèse est consacré au développement d'un outil numérique capable de modéliser la propagation 3D d'ondes sismiques dans les milieux géologiques complexes caractérisés par des effets de site. La méthode des éléments spectraux (SEM) est particulièrement adaptée à la problématique de la réponse sismique dans de tels milieux: estimation précise des ondes de surface, capacité à prendre en compte des géométries compliquées (topographie des surfaces libres, interfaces) et possibilité d'ajuster la résolution des longueurs d'ondes sismiques dans des conditions de milieux hétérogènes par des maillages non-structurés. Des extensions numériques de la SEM liées à la réponse de bassin ont été développées: Perfectly Matched Layers filtrantes et introduction efficace d'un champ incident. La principale limitation actuelle des SEM reste cependant liée au manque de flexibilité des maillages hexaédriques malgré l'utilisation de ces maillages non-structurés dont la génération constitue une tâche complexe. Ce travail de thèse souligne ainsi les difficultés associées à la prise en compte de telles structures et décrit le processus complet qu'implique la modélisation de la réponse sismique dans des milieux géologiques complexes, de l'élaboration du modèle physique et numérique à l'analyse des résultats. Je présente des simulations 3D de la réponse sismique dans la région de Caracas (Venezuela), incluant la géométrie 3D du bassin et la chaîne de montagnes Ávila qui borde la ville. L'importance des effets liés à ces deux types de structures est évaluée, par différents scénarios d'excitation par une onde plane. Ces effets géométriques 3D révèlent des phénomènes complexes d'amplification associés à la réflexion et à la focalisation d'ondes se propageant dans toutes les directions, ainsi qu'à la génération d'ondes de surface au niveau des bords et des zones de rétrécissement du remplissage sédimentaire. Une comparaison avec des simulations 2D montre l'intérêt d'une modélisation 3D, de nettes différences en terme de temps de résidence et de niveau d'énergie et d'amplification ayant été constatées
Books on the topic "Topographic site effect":
1
Mehmet, Çelebi, and Geological Survey (U.S.), eds. Seismic site-response experiments following the March 3, 1985 central Chile earthquake: Topographical and geological effects. [Reston, Va.?]: U.S. Geological Survey, 1986.
2
Mehmet, Çelebi, and Geological Survey (U.S.), eds. Seismic site-response experiments following the March 3, 1985 central Chile earthquake: Topographical and geological effects. [Reston, Va.?]: U.S. Geological Survey, 1986.
3
Mehmet, Çelebi, and Geological Survey (U.S.), eds. Seismic site-response experiments following the March 3, 1985 central Chile earthquake: Topographical and geological effects. [Reston, Va.?]: U.S. Geological Survey, 1986.
4
Fentress, Elizabeth. Topographic Memory. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198777601.003.0018.
Abstract:
Among the various forms of social memory discussed by Chris Wickham and James Fentress in Social Memory, topographic memory was given rather short shrift: by this I mean the memory formed by and attached to places. To illustrate this theme I chose three sites with a Roman past: Cosa (Ansedonia), the monastery of S. Sebastiano at Alatri, and finally Volubilis in Morocco. These illustrate three different ways in which local memory of Roman sites was transmitted into the Middle Ages, and the reciprocal effects of this memory on the sites themselves, and on those who lived there.
5
Seismic site-response experiments following the March 3, 1985 central Chile earthquake: Topographical and geological effects. [Reston, Va.?]: U.S. Geological Survey, 1986.
6
Seismic site-response experiments following the March 3, 1985 central Chile earthquake: Topographical and geological effects. [Reston, Va.?]: U.S. Geological Survey, 1986.
7
Valenti, Marco. Changing Rural Settlements in the Early Middle Ages in Central and Northern Italy. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198777601.003.0012.
Abstract:
Archaeological sites of this period reveal the continued existence of a very ruralized society. The countryside, subject to a significant strengthening of economic control, was the primary source of wealth and success for the middle and upper social strata that invested in it. Choosing to optimize the exploitation of agricultural land led defining settlements in a more urban way. Since rural sites were the spaces where the labour force was ‘anchored’, they were often fortified to protect assets. Examples include both large lay and ecclesiastical aristocratic landowners and more local elites all over Italy. In the vast majority of cases we have fortified villages that are, in fact, agricultural holdings (manorial estates). In any context, the signs of material power exercised by a dominant figure include the management and a very pronounced control of activities, goods, foodstuffs, and labour, which find their counterpart in features and topography of rural centres. Settlements where production is aimed at wealth accumulation, often defended even from insiders by separating the spaces of power from those of the peasant masses, are frequently observed archaeologically. This is evidenced by the structural changes taking place both in the villages and in the single residential building types, serving as signs of a significant effort devoted to the centralization of production means (animals, tools, craft-shops), in order to increase what appears to be the main objective of landed elites: managing territorial resources in order to store foodstuffs, not only for personal consumption but also for to sell them in urban markets; in other words, to produce wealth.
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Galadza, Daniel. Liturgy and Byzantinization in Jerusalem. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198812036.001.0001.
Abstract:
The church of Jerusalem, the ‘mother of the churches of God’, influenced all Christendom before it underwent multiple captivities between the eighth and thirteenth centuries: first, political subjugation to Arab Islamic forces, then displacement of Greek-praying Christians by crusaders, and, finally, ritual assimilation to fellow Orthodox Byzantines in Constantinople. All three contributed to the phenomenon of the Byzantinization of Jerusalem’s liturgy, but only the last explains how the latter was completely lost and replaced by the liturgy of the imperial capital, Constantinople. The basis of this study is the rediscovered manuscripts of Jerusalem’s liturgical calendar and lectionary. When examined in context, they reveal that the devastating events of the Arab conquest in 638 and the destruction of the Holy Sepulchre in 1009 did not have as detrimental an effect on liturgy as previously held. They confirm that the process of Byzantinization was gradual and locally implemented rather than an imposed element of Byzantine imperial policy or ideology from the church of Constantinople. Originally the city’s worship consisted of reading Scripture and singing hymns at places connected with the life of Christ, so that the link between holy sites and liturgy became a hallmark of Jerusalem’s worship; but the changing sacred topography caused changes in the local liturgical tradition. This book is the first monograph dedicated to the question of the Byzantinization of Jerusalem’s liturgy; it provides for the first time English translations of many liturgical texts and hymns and offers a glimpse of Jerusalem’s lost liturgical and theological tradition.
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Ślusarski, Marek. Metody i modele oceny jakości danych przestrzennych. Publishing House of the University of Agriculture in Krakow, 2017. http://dx.doi.org/10.15576/978-83-66602-30-4.
Abstract:
The quality of data collected in official spatial databases is crucial in making strategic decisions as well as in the implementation of planning and design works. Awareness of the level of the quality of these data is also important for individual users of official spatial data. The author presents methods and models of description and evaluation of the quality of spatial data collected in public registers. Data describing the space in the highest degree of detail, which are collected in three databases: land and buildings registry (EGiB), geodetic registry of the land infrastructure network (GESUT) and in database of topographic objects (BDOT500) were analyzed. The results of the research concerned selected aspects of activities in terms of the spatial data quality. These activities include: the assessment of the accuracy of data collected in official spatial databases; determination of the uncertainty of the area of registry parcels, analysis of the risk of damage to the underground infrastructure network due to the quality of spatial data, construction of the quality model of data collected in official databases and visualization of the phenomenon of uncertainty in spatial data. The evaluation of the accuracy of data collected in official, large-scale spatial databases was based on a representative sample of data. The test sample was a set of deviations of coordinates with three variables dX, dY and Dl – deviations from the X and Y coordinates and the length of the point offset vector of the test sample in relation to its position recognized as a faultless. The compatibility of empirical data accuracy distributions with models (theoretical distributions of random variables) was investigated and also the accuracy of the spatial data has been assessed by means of the methods resistant to the outliers. In the process of determination of the accuracy of spatial data collected in public registers, the author’s solution was used – resistant method of the relative frequency. Weight functions, which modify (to varying degree) the sizes of the vectors Dl – the lengths of the points offset vector of the test sample in relation to their position recognized as a faultless were proposed. From the scope of the uncertainty of estimation of the area of registry parcels the impact of the errors of the geodetic network points was determined (points of reference and of the higher class networks) and the effect of the correlation between the coordinates of the same point on the accuracy of the determined plot area. The scope of the correction was determined (in EGiB database) of the plots area, calculated on the basis of re-measurements, performed using equivalent techniques (in terms of accuracy). The analysis of the risk of damage to the underground infrastructure network due to the low quality of spatial data is another research topic presented in the paper. Three main factors have been identified that influence the value of this risk: incompleteness of spatial data sets and insufficient accuracy of determination of the horizontal and vertical position of underground infrastructure. A method for estimation of the project risk has been developed (quantitative and qualitative) and the author’s risk estimation technique, based on the idea of fuzzy logic was proposed. Maps (2D and 3D) of the risk of damage to the underground infrastructure network were developed in the form of large-scale thematic maps, presenting the design risk in qualitative and quantitative form. The data quality model is a set of rules used to describe the quality of these data sets. The model that has been proposed defines a standardized approach for assessing and reporting the quality of EGiB, GESUT and BDOT500 spatial data bases. Quantitative and qualitative rules (automatic, office and field) of data sets control were defined. The minimum sample size and the number of eligible nonconformities in random samples were determined. The data quality elements were described using the following descriptors: range, measure, result, and type and unit of value. Data quality studies were performed according to the users needs. The values of impact weights were determined by the hierarchical analytical process method (AHP). The harmonization of conceptual models of EGiB, GESUT and BDOT500 databases with BDOT10k database was analysed too. It was found that the downloading and supplying of the information in BDOT10k creation and update processes from the analyzed registers are limited. An effective approach to providing spatial data sets users with information concerning data uncertainty are cartographic visualization techniques. Based on the author’s own experience and research works on the quality of official spatial database data examination, the set of methods for visualization of the uncertainty of data bases EGiB, GESUT and BDOT500 was defined. This set includes visualization techniques designed to present three types of uncertainty: location, attribute values and time. Uncertainty of the position was defined (for surface, line, and point objects) using several (three to five) visual variables. Uncertainty of attribute values and time uncertainty, describing (for example) completeness or timeliness of sets, are presented by means of three graphical variables. The research problems presented in the paper are of cognitive and application importance. They indicate on the possibility of effective evaluation of the quality of spatial data collected in public registers and may be an important element of the expert system.
Book chapters on the topic "Topographic site effect":
1
Cao, Qun, and Lin Qiu. "Research on Atmospheric Dispersion Factor Used in the Calculation of Emergency Planning Zone." In Springer Proceedings in Physics, 257–69. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_24.
Abstract:
AbstractReasonable division of emergency planning zones is an important technical basis for emergency preparedness and responses. In order to evaluate the size of the emergency planning zone, it’s important to determine the appropriate atmospheric dispersion factor based on the realistic site conditions to calculate the dose consequences caused by the accident through the radioactive plume. This paper introduces the current progress in the calculation of emergency planning zoning for different reactor nuclear power plant sites, the general method of determining the emergency planning zone in China and puts forward the method for optimizing the calculation of the atmospheric dispersion factor used in the emergency planning zoning for HPR1000 nuclear power plant site. Based on the theoretical analysis and comparison of the current main calculation models of atmospheric dispersion factor, this paper is devoted to the feasibility analysis of use of Gaussian puff models in the EPZ calculation considering the light wind and the calm wind condition, which can obtain the convergence results. This model can fully consider the dispersion process, spatial variation of meteorological fields, topographic effects and accumulation of pollutants and greatly improve the calculation accuracy. To solve the problems of low calculation speed brought by Gaussian puff models used in the EPZ calculation, the paper makes a theoretical analysis of the current main weather sampling methods and puts forward the stratified random sampling method to improve the speed of EPZ calculation. This method can select representative weather samples from the annual weather sequences to represent the annual situation so as to speed up the calculation without affecting the calculation accuracy.
2
Yang, Lixiang, Yaobin Han, Xu Zhang, and Zhiwen Li. "Numerical Simulation for the Dynamic Response of Step Topography Subjected to Blasting Load." In Lecture Notes in Civil Engineering, 179–86. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2532-2_15.
Abstract:
AbstractThe vibration velocity and frequency of rock mass are closely related to the instability and failure of the building. The step topography has great influence on blasting vibration wave propagation. Therefore, it is of great significance to study the dynamic response of step topography subjected to blasting load. In this paper, the FLAC2D program is used to study the dynamic response of step topography subjected to blasting load. The plane strain mode is adopted in the calculation, and the blasting load is assumed to be a triangular pulse wave which is applied to one side of the calculating mode. The amplification effect of the height of the step is first studied. The calculation result shows that the amplification factor increases first and then decreases with the increase of the step height. The maximum value of the amplification factor is consistent with the results of the field test, which indicates the feasibility of the numerical simulation.
3
Miyagi, Toyohiko, Koji Ikeda, Haruna Ishikawa, Loi Doan, Nguyen Kim Thanh, Pham Van Tien, Yuxin Li, and Feng Zhang. "Interpretation and Mapping for the Prediction of Sites at Risk of Landslide Disasters: From Aerial Photography to Detection by DTMs." In Progress in Landslide Research and Technology, Volume 3 Issue 1, 2024, 15–61. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-55120-8_2.
Abstract:
AbstractBy grasping the slope topography three-dimensionally and typifying and mapping the landform features, it is possible to visualize the areas at risk of landslide-induced disasters. This effort began with the interpretation of aerial photographs, and, in recent years, has shown great development with the advancement of remote sensing technology. In this chapter, we introduce the characteristics that can be extracted from remote sensing data that can be used to identify potential areas exposed to mass movement processes and landslide-induced disasters. In addition, we created a manual for landslide recognition by aerial photographs, AW3D-based wide-area maps, and specific landslide microtopography maps, which can be freely used to identify landslide landforms.
4
Boose, Emery R. "Hurricane Impacts in New England and Puerto Rico." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0008.
Abstract:
Hurricanes have a profound effect on many coastal ecosystems. Direct impacts often include wind damage to trees, scouring and flooding of river channels, and salt-water inundation along shorelines (Simpson and Riehl 1981; Diaz and Pulwarty 1997). In some areas, secondary impacts may include landslides triggered by heavy rains (Scatena and Larson 1991) or catastrophic dry-season fires resulting from heavy fuel loading (Whigham in press). This chapter will focus on the longterm impacts of hurricane wind damage at two LTER sites, the Harvard Forest (HFR) in central New England and the Luquillo Experimental Forest (LUQ) in northeastern Puerto Rico. These two sites, both located in the North Atlantic hurricane basin and occasionally subject to the same storms, provide interesting examples of tropical and temperate hurricane disturbance regimes. Wind damage from a single hurricane is often highly variable (Foster 1988). Damage to individual trees can range from loss of leaves and fine branches, which can significantly alter surface nutrient inputs (Lodge et al. 1991), to bole snapping or uprooting, which can significantly alter coarse woody debris and soil microtopography (Carlton and Bazzaz 1998a and b). At the stand level, damage can range from defoliation to individual tree gaps to extensive blowdowns, creating different pathways for regeneration (Lugo 2000). At landscape and regional levels, complex patterns of damage are created by the interaction of meteorological, topographic, and biological factors (Boose et al. 1994). Adding to this spatial complexity is the fact that successive hurricanes are not necessarily independent in terms of their effects. A single storm lasting several hours may have effects that persist for decades (Foster et al. 1998). And forest susceptibility to wind damage is strongly influenced by composition and structure, which in turn are strongly influenced by previous disturbance history (Foster and Boose 1992). Thus, the impacts of a single hurricane may depend in part on the impacts of earlier storms as well as on other previous disturbances and land use. Hurricanes, like other disturbances, both create and respond to spatial heterogeneity (Turner et al. 2003). To understand the long-term ecological role of hurricanes at a given site, we must consider these three sets of questions: (1) What is the hurricane disturbance regime?
5
Uyanık, Osman, Nurten Ayten Uyanık, and Nevbahar Ekin. "Local Site Effects Evaluation Using Geophysical Methods." In Advances in Environmental Engineering and Green Technologies, 23–56. IGI Global, 2023. http://dx.doi.org/10.4018/979-8-3693-0819-6.ch002.
Abstract:
The waves that occur in an earthquake affect the behavior of the soil and the building due to the structural condition of the bedrock and the physical properties of the soil near the surface. To predict this interaction, the deep underground structure models of the areas considered as settlements should be determined and how the earthquake waves will be directed (macro-zoning) depending on this should be revealed. Since the near surface features of the ground can increase the effect of earthquake waves, it is necessary to determine the near surface properties and create their maps (micro-zoning). Earthquake waves are formed in thick sediments compared to the rock environment and cause great damage to both the ground and the buildings. In order to be protected from these damages, it is necessary to determine focusing and scattering conditions arising from the deep underground base topography. Therefore, parameters such as maximum horizontal ground acceleration, soil liquefaction, soil dominant vibration period, soil amplification, and near-surface soil properties should be determined.
6
"Effects of Urbanization on Stream Ecosystems." In Effects of Urbanization on Stream Ecosystems, edited by Cathy M. Tate, Thomas F. Cuffney, Gerard McMahon, Elise M. P. Giddings, James F. Coles, and Humbert Zappia. American Fisheries Society, 2005. http://dx.doi.org/10.47886/9781888569735.ch17.
Abstract:
<em>Abstract.</em>—To assess the effects of urbanization on assemblages (fish, invertebrate, and algal), physical habitat, and water chemistry, we investigated the relations among varying intensities of basin urbanization and stream ecology in three metropolitan areas: the humid northeastern United States around Boston, Massachusetts; the humid southeastern United States around Birmingham, Alabama; and the semiarid western United States around Salt Lake City, Utah. A consistent process was used to develop a multimetric urban intensity index (UII) based on locally important variables (land-use/land-cover, infrastructure, and socioeconomic variables) in each study area and a common urban intensity index (CUII) based on a subset of five variables common to all study areas. The UII was used to characterize 30 basins along an urban gradient in each metropolitan area. Study basins were located within a single ecoregion in each of the metropolitan areas. The UII, ecoregions, and site characteristics provided a method for limiting the variability of natural landscape characteristics while assessing the magnitude of urban effects. Conditions in Salt Lake City (semiarid climate and water diversions) and Birmingham (topography) required nesting sites within the same basin. The UII and CUII facilitated comparisons of aquatic assemblages response to urbanization across different environmental settings.
7
"Benthic Habitats and the Effects of Fishing." In Benthic Habitats and the Effects of Fishing, edited by Page C. Valentine, Brian J. Todd, and Vladimir E. Kostylev. American Fisheries Society, 2005. http://dx.doi.org/10.47886/9781888569605.ch18.
Abstract:
<strong><em>Abstract. </em></strong>Habitats are defined as spatially recognizable areas where the physical, chemical, and biological environment is distinctly different from surrounding environments. A habitat can be delimited as narrowly or as broadly as the data and purpose permit, and this flexibility of scale influences the development of habitat classification schemes. Recent habitat classifications focus on a wide range of habitats that occur in European, American, and worldwide seafloor environments. The proposed classification of marine sublittoral habitats is based on recent studies in the American and Canadian parts of northeastern North America using multibeam and side-scan sonar surveys, video and photographic transects, and sediment and biological sampling. A guiding principle in this approach to habitat classification is that it will be useful to scientists and managers of fisheries and the environment. The goal is to develop a practical method to characterize the marine sublittoral (chiefly the subtidal continental shelf and shelf basin) habitats in terms of (1) their topographical, geological, biological, and oceanographical attributes and (2) the natural and anthropogenic processes that affect the habitats. The classification recognizes eight seabed themes (informal units) as the major subject elements of the classification. They are seabed topography, dynamics, texture, grain size, roughness, fauna and flora, habitat association and usage, and habitat recovery from disturbance. Themes include one or many classes of habitat characteristics related to seabed features, fauna and flora, and processes that we view as fundamental for recognizing and analyzing habitats. Within the classes, a sequence of subclasses, categories, and attributes addresses habitat characteristics with increasing detail. Much of the classification is broadly applicable worldwide (excluding some lowlatitude environments), but faunal and floral examples are representative of the northeastern North America region. In naming habitats, the classification emphasizes seabed substrate dynamics, substrate type, and seabed physical and biological complexity. The classification can accommodate new classes, subclasses, categories, and attributes, and it can easily be modified or expanded to address habitats of other regions. It serves as a template for a database that will provide a basis for organizing and comparing habitat information and for recognizing regional habitat types.
8
Gupta, Divya, Rimpi Kumari, Amena Salim, Rahul Singhal, and Sanjeev Aggarwal. "Fabrication of Variable Morphologies on Argon Sputtered PMMA Surfaces." In Nanotechnology and Nanomaterials. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.112218.
Abstract:
Ion beam induced patterning and fabrication of various topographies over polymeric surfaces has drawn strong interest due to latent applications in photonics, magnetic devices, optical devices and photovoltaics etc. In this work, we report the controlled surface structuring and evolution of different morphologies in Poly(methyl methacrylate) polymer using Ar+ ion beam fabrication technique. Morphological and structural analysis has been performed by ex situ Atomic Force Microscopy (AFM) and X-ray Diffraction. The effect of oblique incidences on argon sputtered films was evaluated by various surface topography and texture parameters, such as Fast Fourier Transforms, surface roughness, skewness, kurtosis. AFM study demonstrates fabrication of transient morphologies over argon sputtered surfaces. One dimensional (1D) cross section scans of surface profiles are determined and morphological features are investigated. The results showed halo peaks in the XRD patterns, which indicate the amorphous nature of this type of polymer. The formation of these surface structures is attributed to the different degree of sputtering yield at different off-normal incidences and preferential sputtering of hydrogen in comparison to carbon in ion sputtered surfaces.
9
Kim, Haeam. "Comparison of Site Response Analysis (SRA) according to ground modelling and structure consideration." In Earthquake Ground Motion [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.1002922.
Abstract:
When an earthquake occurs, the seismic motion is amplified as it passes through the ground layers. In addition, even for the same earthquake, the magnitude of the ground response on the ground surface varies depending on the ground condition. Determining the response within the ground following an earthquake is called site response analysis (SRA), and a general standard procedure is to perform site response analysis using the 1D (one-dimensional) wave propagation theory. However, in the case of one-dimensional site response analysis, complex topography, ground surface changes, and effects on structures are not included. Therefore, evaluating the reasonable ground response that may occur in the actual field is necessary. This article analyses ground amplification phenomena according to modelling differences through 2D (two-dimensional) and 3D (three-dimensional) modelling that can consider complex topography in addition to 1D. In addition, the nonlinear characteristics of the soil and the interaction between the soil and the structure were considered, and time history analysis was performed to identify the realistic dynamic behaviour characteristics of the soil and structure.
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"Benthic Habitats and the Effects of Fishing." In Benthic Habitats and the Effects of Fishing, edited by R. A. Coggan, C. J. Smith, R. J. A. Atkinson, K. N. Papadopoulou, T. D. I. Stevenson, P. G. Moore, and I. D. Tuck. American Fisheries Society, 2005. http://dx.doi.org/10.47886/9781888569605.ch22.
Abstract:
Traditional methods for assessing the impact of towed demersal fishing gear are notoriously slow, taking years to report and imposing undesirable delays in the provision of scientific advice on which fisheries and environmental managers can act. There is a need to develop rapid methods for assessing trawl impacts. We evaluate and compare a suite of rapid methodologies covering a range of readily accessible technologies including: (1) Acoustic methods: sidescan sonar and bottom discriminating sonar (RoxAnn); (2) Visual methods: towed video sledge and ROV; (3) Faunal sampling (epibenthic megafauna): tissue damage, community analysis, population density, functional group composition; and (4) Sedimentology: granulometry, geotechnical properties and sediment profile imagery. These methods were applied to otter trawl fisheries in the Clyde Sea, Scotland and the Aegean Sea, Mediterranean, at sites representing a range of trawl impacts. Novel methods of analysis were developed for quantitative interpretation of sidescan and video records. The scientific effectiveness, cost effectiveness and operational constraints of the various methodologies are reviewed. We recommend suitable approaches to the rapid assessment of trawl impacts taking into consideration the variety of resources (such as time, equipment and budget) which may be available. Assessments should employ complementary methods that operate on different scales of resolution (eg. sidescan sonar with either faunal sampling or ROV). Site-specific factors, such as topography and substratum type, will influence choice of methods and survey design. These rapid methodologies can provide results in a matter of days or weeks rather than the months or years associated with traditional assessment methods.
Conference papers on the topic "Topographic site effect":
1
Dong, Xinwen, Sheng Fang, and Shuhan Zhuang. "SWIFT-RIMPUFF Modeling of Air Dispersion at a Nuclear Powerplant Site With Heterogeneous Upwind Topography." In 2021 28th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/icone28-64608.
Abstract:
Abstract The SWIFT-RIMPUFF can provide refined atmospheric dispersion modeling for nuclear emergency response, but its performance for the mesoscale range in a nuclear power plant (NPP) site with highly complex topographies hasn’t been fully investigated. In this study, a validation of SWIFT-RIMPUFF was performed based on a wind tunnel experiment simulating a real China’s multi-reactor NPP site with heterogeneous upwind topography and dense buildings to understand the potential discrepancies or limits. The results demonstrate that the SWIFT-RIMPUFF can reproduce the sharp changes of wind flows for both speed and directions near the buildings, but usually overestimate the wind speed in the complex topography. For vertical wind profiles, the accuracies show high dependencies on the local topography and building layout, and the deviation of those near the building is more obvious. The simulated ground concentrations match the topographic changes of high-altitude mountains. The concentration predictions in the downwind building area are acceptable which displays that the influence of building effects can be well introduced, but the simulations in the building area still show noticeable discrepancies when compared with those in the sea area. However, such deviations do not propagate to the downwind mountainous and sea areas, which the accuracies are quite satisfactory.
2
Varela, Antonia M., Casiana Muñoz-Tuñón, Begoña García-Lorenzo, and Jesús J. Fuensalida. "Tropospheric wind regimes and site topographical effects: importance for site characterization." In SPIE Astronomical Telescopes + Instrumentation, edited by Larry M. Stepp. SPIE, 2006. http://dx.doi.org/10.1117/12.671387.
3
Waikar, R. A., and Y. B. Guo. "The Synergistic Effect of Tool Geometry and Hard Turning vs. Grinding Processes on 3D Surface Micro Topography." In ASME 2007 International Manufacturing Science and Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/msec2007-31086.
Abstract:
Surface topography induced by precision machining is critical for component performance. This paper is to study the synergistic effects of work materials, machining processes, and tool geometry on the geometrical surface quality. Four representative surface topographies of turned and ground surfaces were prepared at “extreme” machining conditions (gentle and abusive) and compared in terms of 3-dimensional (3D) surface features of amplitude, area and volume, spatial, and hybrid parameters. The 3D surface topography maps revealed the anisotropic and repeatable nature of a turned surface which was in sharp contrast with the random and isotropic nature of a ground surface. In general, a gentle turned surface has higher values of amplitude parameters (arithmetic mean, root mean square, maximum height of summits, maximum depth of valleys, and ten-point height) than an abusively turned surface, whereas the opposite was true for the ground counterparts. Only the gentle ground surface has a negative skewness which means that the topography distribution is more biased towards the valley side. The larger kurtosis value of the abusively ground surface implies a more peaked surface topography. The gentle ground and abusively turned surfaces have a much larger bearing area ratio and therefore better bearing capacity than the gentle turned and abusively ground ones. The abusively ground surface has higher fluid retainability than other surfaces in terms of mean void volume.
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Mohammadi, K., and D. Asimaki. "Topography Effects Are Not Dominated by Ground Surface Geometry: A Site Effects Paradox." In Geotechnical Frontiers 2017. Reston, VA: American Society of Civil Engineers, 2017. http://dx.doi.org/10.1061/9780784480489.018.
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Shuai, Li, Wang Ming-dong, Zhang Fan, Wang Jing-quan, Zhang Yu, Dai Deng-hui, Zhang Ning, and Gao Yu-feng. "Seismic Performance Assessment of Multi-Span Continuous Railway Bridges Across a Symmetrical V-Shaped Canyon Considering the Near-Source Topographic Effect." In IABSE Congress, Nanjing 2022: Bridges and Structures: Connection, Integration and Harmonisation. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2022. http://dx.doi.org/10.2749/nanjing.2022.1396.
Abstract:
<p>Topographic features have remarkable influences on the characteristics of ground motions, which may cause the amplification of input seismic waves. The objective of this study is to numerically explore the near-source topographic effects on the seismic behaviors of an existing railway bridge crossing a symmetrical V-shaped canyon. Numerical results demonstrated that the topographic effects can noticeably amplify the seismic responses of the bridge. Compared to the bridge without crossing a canyon, the peak displacement of the girder and pier in the case of the canyon- crossing bridge increases by 15.2% and 2.9%-14.5%, respectively. The piers at the illuminated side of the canyon experience larger seismic responses compared to the piers at the shaded side of the canyon due to the unequal motion amplitudes at each support.</p>
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Jin, D. D., G. X. Chen, and F. F. Dong. "Seismic Response of a Real Basin Site Considering Topography Effect and Nonlinear Characteristic of Soil." In Sixth China-Japan-US Trilateral Symposium on Lifeline Earthquake Engineering. Reston, VA: American Society of Civil Engineers, 2013. http://dx.doi.org/10.1061/9780784413234.070.
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Aluker, N., and А. Artamonov. "Ensuring radiation safety of medical examinations using thermoluminescent dosimetry." In 8th International Congress on Energy Fluxes and Radiation Effects. Crossref, 2022. http://dx.doi.org/10.56761/efre2022.r5-p-047801.
Abstract:
The paper proposes the use of TLD-K thermoluminescent detectors for measuring absorbed doses at the entrance and exit radiation sites of the patient's body during medical diagnostic examinations. The proposed technique is used in dosimetric control of patients during diagnostic examinations and medical personnel working under X-ray control. The use of small-scale thermoluminescent detectors with cover layers of different thicknesses makes it possible to study the topography of dose distribution both in terms of propagation depth and body area.
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Rispal, Lorraine, Yordan Stefanov, Rudolf Heller, Gerhard Tzschockel, Gisela Hess, Klaus Haberle, and Udo Schwalke. "Topographic and Conductive AFM Measurements on Carbon Nanotube Field-Effect Transistors Fabricated by In-situ Chemical Vapor Deposition." In 2005 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 2005. http://dx.doi.org/10.7567/ssdm.2005.g-7-4.
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Woodin, Craig, Harsha Malshe, and Shreyes Melkote. "Effects of Single Point Dressing on Seeded Gel Grinding Wheel Surface Topography." In ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/msec2014-4169.
Abstract:
The effects of single point dressing on the surface topography of a seeded gel (SG) ceramic grinding wheel are investigated. First, new wheel and grain characterization techniques including X-ray micro-tomography (μCT) are introduced to obtain a better understanding of the micro surface topography of the SG grinding wheel. Single point dressing experiments are then carried out and the resulting wheel topography evaluated using optical surface metrology to understand the effects of dressing parameters. A special wheel indexing and relocation apparatus is designed and used to analyze changes in wheel surface topography at a given location before and after dressing. In addition, statistical distributions of the key parameters (e.g. grit density, grit size, grit height, number of sides of grit, grit spacing) are determined and analyzed.
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Li-Lung, Lai, Huimin Gao, and Hong Xiao. "Surface Effect on SEM Voltage Contrast and Dopant Contrast." In ISTFA 2009. ASM International, 2009. http://dx.doi.org/10.31399/asm.cp.istfa2009p0202.
Abstract:
Abstract The Voltage Contrast (VC) [1-3] and Dopant Contrast [4-7] in Scanning Electron Microscopy (SEM) [8] have been widely used in the Silicon (Si) semiconductor manufacturing field to localize the failure site from plane-view and inspect the doping profile along cross-section with spatial resolution in the nanometer (nm) range. In this article, we demonstrate how the surface effect, such as topography or material variation, impacts the conventional prediction for the voltage and dopant contrast in the SEM images. The mechanisms and applications for the SRAM and real products are described.
Reports on the topic "Topographic site effect":
1
Swan, Megan, and Christopher Calvo. Site characterization and change over time in semi-arid grassland and shrublands at three parks?Chaco Culture National Historic Park, Petrified Forest National Park, and Wupatki National Monument: Upland vegetation and soils monitoring 2007?2021. National Park Service, 2024. http://dx.doi.org/10.36967/2301582.
Abstract:
This report presents results of upland vegetation and soil monitoring of semi-arid grasslands at three Parks by the Southern Colorado Plateau Inventory and Monitoring Network (SCPN) from 2007?2021. The purpose is to compare and contrast five grassland ecological sites and examine how they have changed during the first 15 years of monitoring. Crews collected data on composition and abundance of vegetation, both at the species level and by lifeform (e.g., perennial grass, shrub, forb) and soil aggregate stability and soil texture at 150 plots within five target grassland/shrubland communities delineated using NRCS ecological site (ecosite) classification (30 plots per ecosite). Soils in plots at Petrified Forest NP and Chaco Culture NHP were deeper than those at Wupatki NM. Undifferentiated soil crust comprised the largest component of the soil surface, except at Wupatki where surface gravel dominated. Cover of biological soil crust (cyanobacteria, lichen, and moss) was low. Soil aggregate stability was moderate. From 2007?2021, SCPN crews identified 283 unique plant species. Overall live foliar cover ranged from 12-24%. Four of five ecological sites were dominated by C4 grass species (>70% of total live foliar cover). Shrubs co-dominated at one site (WUPA L) and forbs were an overall small component of total vegetation cover but contributed most of the diversity in these sites. Less than 4% of species detected were nonnative. Russian thistle (Salsola tragus) was the most frequently sampled nonnative, occurring in > 50% of plots at Wupatki in the volcanic upland ecological site. Cheatgrass (Bromus tectorum) was the second most common invasive species but occurred in < 10% of the plots at all ecological sites. Vegetation cover was modeled using Bayesian hierarchical models and included seasonal climatic water deficits, year effects and topographic variables as covariates. Models revealed significant negative time trends (i.e., changes over time that were not explained by changes in seasonal deficit covariates included) in some modeled responses, particularly in the cover of perennial grass at all five ecological sites. Time trends in shrub and forb responses were mixed. Species richness showed variable effects by ecosite, decreasing at CHCU S, and increasing at PEFO S and WUPA V. Modeled responses were influenced by climate covariates, but direction of these effects varied. The most consistent effects were that greater July water stress and higher accumulated growing degree days (i.e., warmer spring temperatures) increased cover of perennial grasses and shrubs during the same year. However, greater water stress in the spring had a negative effect on many responses as expected. Decreasing cover of perennial grass and increasing cover of shrubs and weedy forbs has been predicted for southwestern grasslands in response to increasing aridification due to anthropogenic climate change. Perennial grass trends reported here correspond with these predictions with mixed results on shrub and forb community trends. Continued drought conditions will likely exacerbate negative changes in these systems.
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Mohammadi, Kami, Domniki Asimaki, and Carene Larmat. Three-Dimensional Site Effects at Mortandad Canyon, NM:I. Validation against ambient noise recordings of topography effects. Office of Scientific and Technical Information (OSTI), November 2021. http://dx.doi.org/10.2172/1829620.
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Butterweck, Gernot, Alberto Stabilini, Benno Bucher, David Breitenmoser, Ladislaus Rybach, Cristina Poretti, Stéphane Maillard, et al. Aeroradiometric measurements in the framework of the swiss exercise ARM23. Paul Scherrer Institute, PSI, March 2024. http://dx.doi.org/10.55402/psi:60054.
Abstract:
The flights of the civil (ARM23c) and military (ARM23m) parts of the exercise were performedbetween June 19th and 23rd and between September 11th and September 15th,respectively. The measuring system RLL001 was employed for all measurements. As usual, during the civil exercise the environs of some of the Swiss nuclear power plants were screened, on behalf of the Swiss Nuclear Safety Inspectorate (ENSI). At the site of the nuclear power plant Gösgen (KKG) with its pressurized water reactor, the activation products of the primary coolant loop are kept in the well shielded reactor building, thus generating no elevated readings neither on the premises nor in the vicinity of the power plant. The nuclear power plant of Mühleberg (KKM) is now being decommissioned. During this phase, activated components are temporarily stored and processed on the plant premises. The dose rate produced by these components, easily detected and identified with the Swiss airborne gamma spectrometry system, is nevertheless very modest and closely monitored by the Swiss Nuclear Safety Inspectorate (ENSI). Search exercises for radionuclide sources were performed in both parts of ARM23. The operational software of the RLL systems was able to detect the radionuclide sources placed in military training areas. The Man-Made Gross-Count (MMGC) ratio demonstrated a good sensitivity for the identification of radionuclide sources. Nevertheless, a weak radionuclide source placed in the field of view of the helicopter (300 m x 300 m at a ground clearance of 100 m) together with a much stronger radionuclide source emitting higher energy photons was obscured due to Compton scattered photons and therefore could not be detected. Measurements of two teams using drones equipped with radiation monitors demonstrated that low flying drones (ground clearance below 10 m) can be a valuable and complementary tool to identify sources and to further reduce the target area to be searched with ground teams. An altitude profile over Lake Constance confirmed the already observed influence of airborne radon progeny on the determination of cosmic and background corrections. Background flights were performed over several Swiss regions. Besides attenuation effects of water bodies, variations of natural radionuclide content could be observed. A new flight strategy in alpine topography was tested near the Swiss mountain Chrüz. Following contour lines of the topography reduces the necessity for drastic flight altitude changes compared to the parallel line pattern normally used, but is much more challenging for the pilots.