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641.
Many hydrothermal deposits are formed around the marine and terrestrial fumarolic vents of Vulcano island (Italy). Their genesis is related to the recombination of the elements brougth by the fumaroles and those liberated by the destruction of pre-existing minerals. 相似文献
642.
P. A. Mohr 《Bulletin of Volcanology》1962,24(1):421-428
Recent Quaternary faulting and vulcanicity accompanied by peculiar subsidence phenomena in the northern part of the Main Ethiopian Rift are described for the first time. A suggested sequence of geological events is given. 相似文献
643.
F. Zebender P. Zimmermann R. Märki A. Hörler H. Ambübl 《Aquatic Sciences - Research Across Boundaries》1961,23(1):296-308
Ohne Zusammenfassung 相似文献
644.
Mini-sosie consists in using a vibration-rammer as seismic source and changing the striking rate by varying the engine speed, resulting in a random impulse transmission. The recording instruments are made up of two seismic traces, two constant gain amplifiers and a two-channel sosie processor which performs the decoding in real time by using the actual transmission times supplied by a captor located on top of the vibration-rammer's plate. An idea of the possible penetration is given by the recording of a velocity survey. Other results obtained in seismic reflection and refraction are given. 相似文献
645.
646.
Magnetotelluric soundings are frequently carried out on a single profile or on profiles remote from each other. Interpretation
of the obtained data is difficult in the presence of spatially heterogeneous geoelectric structures. We evaluate its capabilities
on the basis of the synthetic data, that correspond to a geoelectric model, which consists of a three-layered section in the
background and three rectangular prisms, differently arranged relative to the profile. Using the simple methods of analysis
of magnetotelluric data, we succeeded in allocating all three heterogeneities over the area that surrounds the profile of
observations. As a result of the fast smoothed-structure 1D and 2D inversion of different components of data, taking into
account their specific features, the depths of the occurrence of anomalies and the order of the values of their electrical
resistivity were evaluated, and the background section was also reconstructed. On this basis, and, also, with the use of a
priori geological-geophysical information, the construction of a 3D model in a more or less broad band around the profile
and its correction with the aid of 3D data inversion are possible. 相似文献
647.
Paul R. Renne Alan L. Deino Willis E. Hames Matthew T. Heizler Sidney R. Hemming Kip V. Hodges Anthony A.P. Koppers Darren F. Mark Leah E. Morgan David Phillips Brad S. Singer Brent D. Turrin Igor M. Villa Mike Villeneuve Jan R. Wijbrans 《Quaternary Geochronology》2009,4(5):346-352
Data reported in 40Ar/39Ar geochronology studies are commonly insufficient to allow computation of ages. This deficiency renders it difficult to compare ages based on different standards or constants, and often hinders critical evaluation of the results. Herein are presented an enumeration of the data that should be reported in all 40Ar/39Ar studies, including a discussion in support of these requirements. The minimum required data are identified and distinguished from parameters that are useful but may be derived from them by calculation. Finally, recommendations are made for metadata needed to document age calculations (e.g., from age spectrum or isochron analyses). 相似文献
648.
This study investigated the effect of urbanization on runoff from the On-Cheon Stream watershed in Pusan, Korea. This watershed has been experiencing considerable urbanization since the 1960s. There are two gauging stations in the watershed. For one of the stations there are recent flow data and for the other flow data were observed in the past. A linear reservoir model was chosen and runoff was analysed for several flood events. The linear reservoir model has been found to generate flood hydrographs accurately for both gauging stations, and its applicability to the study area has also been established. Using two methods of computing effective rainfall or rainfall excess (ϕ-index and constant percentage method), the results of runoff analyses were investigated. The ϕ-index method yielded better results than the constant percentage method. A comparison of hydrographs observed in the past with the simulation results at the Ie-Sup bridge site revealed that the peak discharge increased and the mean lag time of the study area decreased owing to urbanization over the past two decades. It is also possible to evaluate the effect of urbanization quantitatively. © 1998 John Wiley & Sons, Ltd. 相似文献
649.
A simple model describing the transformation of effective rainfall to direct runoff through the overland flow mechanism is presented. The model is based on the classical representation of a watershed by a combination of planes and channels. The dynamics of overland flow in each plane is simulated by the non-linear kinematic wave, but the outflow from a given plane is concentrated in the middle of the corresponding drainage channel. The water routing in the channels is carried out by a piece-wise linearized formulation in space of the kinematic wave approximation. Using synthetic events on 10 watersheds, the model was tested by comparing it with results obtained by applying the non-linear kinematic wave to all the elements of the watershed. The model was found to be adequate, even in a form that simplifies the geometric features of the planes through an averaging procedure based on the Horton–Strahler ordering scheme of the watershed. © 1998 John Wiley & Sons, Ltd. 相似文献
650.
Sanz Pérez E 《Ground water》2001,39(2):203-209
Specific functions of distribution of the number of springs and of their contributions according to flow for each of nine lithological groups are established. These functions confirm the suitability of a general type of distribution (Sanz 1996), which is a borderline case of the lognormal distribution. The statistical methods proposed for the lithological types presented can be applied to any region if data on flow and lithology of the aquifers drained by springs are available. These methods have been applied to Spain, a representative region with varied geology, climate and topography; 71.2% of spring flow is supplied by limestones, 19.17% by alluvial sediments and marls, 6.7% by conglomerates and sandstones, and 3% by slates, plutonic rocks, quartzites, and other groups. Springs with discharge rates exceeding 2000 L/s exist only in limestones. The majority of springs with low flow occur in marls. If we consider springs with flow greater than 0.5 L/s, alluvial sediments, sandstones, marls, and limestones have the greatest density of springs per surface area, although the average flow varies greatly from one lithology to the next. The cumulative estimated discharge and the estimated number of springs depend upon the definition of the lower limit of flow. For example, total discharge is reduced by 30% if we eliminate all springs with flow lower than 0.5 L/min. 相似文献