A priority task for correct environmental planningis to evaluate Natural Hazards, especially inhighly populated areas. In particular, thoroughinvestigations based on different Earth Sciencetechniques must be addressed for the Seismic HazardAssessment (SHA) in tectonically active areas. Notonly the management but also the multidisciplinaryanalysis of all the SHA-related data sets is bestperformed using a Geographic Information System. In this paper we show how a research-oriented GIS isbuilt and used in a practical case. The GeochemicalGeographic Information System (G2IS) wasdeveloped and applied to the Gargano promontory(southern Italy) in the framework of an EC researchproject, the Geochemical Seismic Zonation (GSZ)Project. This multidisciplinary – multiscalingpowerful tool is described in its structure, updatingprocedures and manipulation techniques. Preliminaryresults are presented on the detection of geochemically active fault zones and theircorrelation with remote sensing data and otherevidences of seismogenic structures. 相似文献
The Central Andean gravity high (CAGH) is a positive anomaly in isostatic residual gravity with its center located at the western flank of the Central Andes at about 24°S. The gravity was analyzed by various methods to draw quantitative conclusions about the sources of this anomaly and their process of formation. Methods include the analysis of the gravity gradients, power spectrum, wavelength filters, and Euler deconvolution.Numerical investigations of gravity field in the area of the CAGH indicate the presence of a dense body of nearly 400 km length and about 100–140 km width, that masses lie at varying depths between 10 and 38 km. A correlation between the location of the residual anomalies and the topographic lows in the area between the Salars de Atacama and Pipanaco is observed, which indicates the strong influence of the anomalous-causing rocks of the CAGH within the formation process of the Andean orogen. An influence of these causing bodies of rock on the trend of Holocene volcanic arc is likely. Genesis of the anomalous dense formations of rock could be traced back to Ordovician–Silurian time when a pre-Andean subduction zone is postulated in the region of northern Chile with its corresponding volcanic arc in the region of the CAGH.
Zusammenfassung
El campo de gravedad alto de los Andes Centrales (CAGH) consiste en una pronunciada anomalía positiva de la gravedad isostática, cuyo centro se encuentra en el borde oeste de los Andes Centrales a los 24°S. En este estudio se analizó el campo de gravedad mediante distintos métodos, de manera de poder establecer conclusiones cuantitativas sobre el causante de esta anomalía y el proceso de formación de este causante.La investigación numérica de las anomalías gravimétricas del CAGH indica la presencia de un cuerpo de alta densidad con aproximadamente 400 km de largo y 100–140 km de ancho, que se encuentra a profundidades variables entre 10 y 38 km. Se observa una correlación entre la posición de la anomalía residual y los bajos topográficos en los areas de Salares de Atacama, Arizaro, Antofalla y Pipanaco, la cual indica una fuerte influencia de rocas productoras de la anomalía en el CAGH, dentro del proceso de formación del orógeno andino. Es probable que estos cuerpos de rocas causantes de la anomalía tengan incluso influencia en el alineamiento del arco volcánico holocénico. La generación de cuerpos de rocas con una densidad anómala puede remontarse al Ordovícico–Silúrico, tiempo para el que postula una subducción pre-Andina en la región del norte de Chile y que corresponde con el arco volcánico en la región del CAGH. 相似文献
IntroductionIn order to gain a clear idea of the deep tectonic environment of Xingtai earthquake area,three wide-angle deep seismic renectionlrefraction profiles have been conducted through the are4they are Yuanshi--Ji'nan profile, Renxian--Wuqing profile and Tat' an--LongyaM inzhou profi I e.The Yuanshi--Ji'nan profile passes through the epicenter of the Ms=7.2 main shock andTat' ~ongyaO--X inzhou profi ie passes through the ep icenter of the Ms=6. 8 earthquake. Duringthe "Eighth Five-… 相似文献
A new mean-field theory of turbulent convection is developed based on the idea that only the small-scale region of the spectrum is considered as turbulence, whereas its large-scale part, including both regular and semi-organized motions, is treated as the mean flow. In the shear-free regime, this theory predicts the convective wind instability, which causes the formation of large-scale semi-organized motions in the form of cells. In the presence of wind shear, the theory predicts another type of instability, which causes the formation of large-scale semi-organized structures in the form of rolls and the generation of convective-shear waves propagating perpendicular to the convective rolls. The spatial characteristics of these structures, such as the minimum size of the growing perturbations and the size of perturbations with the maximum growth rate, are determined. This theory might be useful for understanding the origin of large-scale cells and rolls observed in the convective boundary layer and laboratory turbulent convection 相似文献
The flux contribution of coherent structures to the total exchange of energy and matter is investigated in a spruce canopy
of moderate density in heterogeneous, complex terrain. The study deploys two methods of analysis to estimate the coherent
exchange: conditional averages in combination with wavelet analysis, and quadrant analysis. The data were obtained by high-frequency
single-point measurements using sonic anemometers and gas analysers at five observation heights above and within the canopy
and subcanopy, and represent a period of up to 2.5 months. The study mainly addresses the momentum transfer and exchange of
sensible heat throughout the roughness sublayer, while results are provided for the exchange of carbon dioxide and water vapour
above the canopy.
The magnitude of the flux contribution of coherent structures largely depends on the method of analysis, and it is demonstrated
that these differences are attributed to differences in the sampling strategy between the two methods. Despite the differences,
relational properties such as sweep and ejection ratios and the variation of the flux contribution with height were in agreement
for both methods. The sweep phase of coherent structures is the dominant process close to and within the canopy, whereas the
ejections gain importance with increasing distance to the canopy. The efficiency of the coherent exchange in transporting
scalars exceeds that for momentum by a factor of two. The occurrence of coherent structures results in a flux error less than
4% for the eddy-covariance method. Based on the physical processes identified from the analysis of the ejection and sweep
phases along the vertical profile in the roughness sublayer, a classification scheme for the identification of exchange regimes
is developed. This scheme allows one to estimate the region of the canopy participating in the exchange of energy and matter
with the above-canopy air under varying environmental conditions. 相似文献
This study proposes a tsunami depositional model based on observations of emerged Holocene tsunami deposits in outcrops located in eastern Japan. The model is also applicable to the identification of other deposits, such as those laid down by storms. The tsunami deposits described were formed in a small bay of 10–20-m water depth, and are mainly composed of sand and gravel. They show various sedimentary structures, including hummocky cross-stratification (HCS) and inverse and normal grading. Although, individually, the sedimentary structures are similar to those commonly found in storm deposits, the combination of vertical stacking in the tsunami deposits makes a unique pattern. This vertical stacking of internal structures is due to the waveform of the source tsunamis, reflecting: 1) extremely long wavelengths and wave period, and 2) temporal changes of wave sizes from the beginning to end of the tsunamis.
The tsunami deposits display many sub-layers with scoured and graded structures. Each sub-layer, especially in sandy facies, is characterized by HCS and inverse and normal grading that are the result of deposition from prolonged high-energy sediment flows. The vertical stack of sub-layers shows incremental deposition from the repeated sediment flows. Mud drapes cover the sub-layers and indicate the existence of flow-velocity stagnant stages between each sediment flow. Current reversals within the sub-layers indicate the repeated occurrence of the up- and return-flows.
The tsunami deposits are vertically divided into four depositional units, Tna to Tnd in ascending order, reflecting the temporal change of wave sizes in the tsunami wave trains. Unit Tna is relatively fine-grained and indicative of small tsunami waves during the early stage of the tsunami. Unit Tnb is a protruding coarse-grained and thickest-stratified division and is the result of a relatively large wave group during the middle stage of the tsunami. Unit Tnc is a fine alternation of thin sand sheets and mud drapes, deposited from waning waves during the later stage of the tsunami. Unit Tnd is deposited during the final stage of the tsunami and is composed mainly of suspension fallout. Cyclic build up of these sub-layers and depositional units cannot be explained by storm waves with short wave periods of several to ten seconds common in small bays. 相似文献