On the Acoustic-Electromagnetic Analogy for the Reflection-Refraction Problem     

Carcione  José M.  Robinson  Enders A. 《Studia Geophysica et Geodaetica》2002,46(2):321-346

The same mathematical theory can be used to describe physical phenomena of different nature. For instance, the wave equation and the related mathematical developments can be used to describe elastic and electromagnetic wave propagation, and it is also extensively used in quantum mechanics. Fresnel's equations are a classical example of the analogy between shear waves and light waves. George Green in the nineteenth century, used analogies to obtain the reflection coefficients for sound waves and light waves, before the advent of the electromagnetic theory of light.In this work, we investigate the mathematical analogy between elastic waves and electromagentic waves. We obtain a complete parallelism for the reflection and refraction problem, considering the most general situation, that is, the presence of anisotropy and attenuation—viscosity in the elastic case and conductivity in the electromagnetic case. The analogy is illustrated with Fresnel's equations, the Brewster and critical angles, the concept of reflectivity and transmissivity, and the corresponding duals fields. The analysis of the elastic-solid theory of reflection applied by Green to light waves, and a brief historical review of wave propagation through the ether, further illustrate the analogy.  相似文献   

Fish zonation in a Mediterranean stream: Effects of human disturbances   总被引：7，自引：0，他引：7  

Anna Vila-Gispert  Emili García-Berthou  Ramon Moreno-Amich 《Aquatic Sciences - Research Across Boundaries》2002,64(2):163-170

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Morphology of the ovotestis of Serranus atricauda (Teleostei,Serranidae)     

María Mercedes García-Díaz  María José Lorente  José Antonio González  Víctor Manuel Tuset 《Aquatic Sciences - Research Across Boundaries》2002,64(1):87-96

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Establishment of a Non-Permanent GPS Network to Monitor the Recent NE-SW Deformation in the Granada Basin (Betic Cordillera,Southern Spain)     

Gil  A. J.  Rodríguez-Caderot  G.  Lacy  M. C.  Ruiz  A. M.  Sanz de Galdeano  C.  Alfaro  P. 《Studia Geophysica et Geodaetica》2002,46(3):395-410

The Granada Basin (Central Betic Cordillera), one of the most seismically active areas of the Iberian Peninsula, is currently subjected to NW-SE compression and NE-SW extension. The present day extension is accommodated by normal faults with various orientations but particularly with a NW-SE strike. At the surface, these active NW-SE normal faults are mainly concentrated on the NE part of the Basin. In this part we have selected a 15-km long segment where several active normal faults crop out. Using the marine Tortonian rocks as a reference, we have calculated a minimum extensional rate of 0.15-0.30 mm/year. The observed block rotation, the listric geometry of faults at depth and the distribution of seismicity over the whole Basin, indicate that this rate is a minimum value. In the framework of an interdisciplinary research project a non-permanent GPS-network has been established in the central sector of Betic Cordillera to monitor the crustal deformations. The first two observation campaigns were done in 1999 and 2000.  相似文献   

Upper Oligocene-Lower Miocene shallowing-upwardlacustrine sequences controlled by periodic and non-periodic processes(Ebro Basin, northeastern Spain)     

Arantxa Luzón  Angel González  Arsenio Muñoz  Belén Sánchez-Valverde 《Journal of Paleolimnology》2002,28(4):441-456

The lacustrine facies from two sections (Candasnos and Fraga) ofthe Oligocene-Miocene Torrente de Cinca lithostratigraphic Unit in thecentral part of the Ebro Basin (Spain) have been analysed to determine theinfluence of orbital parameters in lacustrine sedimentation. The unit ispredominantly composed of limestones and marls, and represents a shallowlacustrine freshwater system. The sedimentological features of the faciesstudied demonstrate that the lower part of the Candasnos section representsoffshore lacustrine subenvironments whereas the upper part, and the whole ofthe Fraga section, characterise marginal lacustrine areas. Series of stratalthickness variations of limestone, marl, and limestone/marl couplets fromboth sections have been analysed using spectral analysis. This shows thatinformation corresponding to periodic cycles only appears in the offshorefacies, that is to say, in the lower part of Candasnos section, and disappearsin the marginal facies where non-periodic cycles exist. Furthermore, thespectral analysis of the offshore facies highlights the existence of a peak inthe power spectrum with a period of around 7 (6.8 to 7.8) that can berecognised in the field as shallowing-upward lacustrine sequences.Magnetostratigraphic data from the Candasnos section allow us to establish atime span of 2,808 years for the limestone/marl couplet from the lower partof this section, and between 19,000 and 22,000 years for the periodic cycleidentified, thus representing the climatic precession cycle. Shallowingsequences from marginal areas do not correspond with any periodiccycle.  相似文献   

Estimates of lichen growth–rate in northern Sweden     

Wibjörn Karlén  & Jessica L. Black 《Geografiska Annaler: Series A, Physical Geography》2002,84(3&4):225-232

Two lichenometric techniques were compared in a study of lichen growth–rate in northern Sweden. The first technique, based on the maximum lichen diameter on glacier moraines, was identical to the technique used in the 1970s, whereas the other utilized the lichen diameter measured on 100 randomly selected boulders. The results indicate that it does not matter which technique is chosen, as long as the technique is used consistently on both the calibration surfaces and the surfaces to be dated. The use of data from both the 1970s and the 2000s increased the number of calibration surfaces available. The new calibration curve indicates that the age of Little Ice Age moraines was underestimated by up to about 30 years in the study conducted in the 1970s.  相似文献   

Mapping brittle fracture zones in three dimensions: high resolution traveltime seismic tomography in a granitic pluton     

D. Martí  R. Carbonell  A. Tryggvason  J. Escuder  A. Pérez-Estaún 《Geophysical Journal International》2002,149(1):95-105

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Modelling and imaging the Moho transition: the case of the southern Urals   总被引：2，自引：0，他引：2  

R. Carbonell  J. Gallart  A. Pérez-Estaún 《Geophysical Journal International》2002,149(1):134-148

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Phénomènes karstiques fossiles et actuels au sein des formations métamorphiques silico-alumineuses de la nappe pan-africaine de Yaoundé (Sud-Cameroun)Fossil and present-time karstic phenomena in silico-aluminous metamorphic formations of the Pan-African nappe of Yaoundé (South-Cameroon)     

Jean-Paul Vicat  Hubert Mvondo  Luc Willems  André Pouclet 《Comptes Rendus Geoscience》2002,334(8):545-550

Numerous karstic features have been recognised in the non-carbonaceous micaschists and gneisses of the Yaoundé Pan-African nappe, south of Cameroon. It is shown that their formation was controlled by the structural features of the rocks. The wells and the pipes in the bedrock outcrops point out a current karstification process, resulting from the plagioclase dissolution by the acid rain waters. Hill wall alveoli and caves, of pre-Miocene age, are exhumed features that were done by dissolution in the aquiferous underground. To cite this article: J.-P. Vicat et al., C. R. Geoscience 334 (2002) 545–550.  相似文献   

La « Mission d'Andalousie », expédition géologique de l'Académie des sciences de Paris à la suite du grand séisme de 1884The ‘Mission d'Andalousie’, a geological expedition of the French Academy of Sciences,following the great Andalusian earthquake of 1884     

Jean Bonnin  Michel Durand-Delga  André Michard 《Comptes Rendus Geoscience》2002,334(10):795-808

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