Frequency-time analysis of geomagnetic beating-type pulsationsPc3     

Karel Prikner  Jaroslav Střeštík  Karel Dobeš  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1974,18(3):266-273

Summary The mechanism of beating of Pc3 type pulsations is studied. Using the method of numerical computation of a sonagram (the method of frequency-time analysis) a set of samples of pulsations from the Budkov Observatory is treated (1968–1969) mostly at K-indices equal to 2–3. By comparing f–t diagrams with the spectra of the samples an attempt has been made at interpreting the beating as a superposition of the frequency components, contained in the pulsation signal. In most observed cases it is possible to determine two close frequencies, the difference of which is on the average =5.4 mHz. The average carrier frequency of the samples was =37.6 mHz, and the average frequency of the beating =2.7 mHz. The interval of observed values of f_B amounted to 1–5 mHz. A tendency was observed for f_B to increase with increasing degree of disturbance of the geomagnetic field.  相似文献   

Zur magnitudenbestimmung der nahbeben     

Vít Kárník 《Studia Geophysica et Geodaetica》1957,1(1):88-94

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L'orage en Suisse     

Flavio Ambrosetti  Max Bider  Max Bouët 《Theoretical and Applied Climatology》1957,8(2):172-184

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Sur la chronologie des fronts froids     

Dr. M. Bouët 《Meteorology and Atmospheric Physics》1968,17(2-3):207-214

Résumé L'étude chronologique des fronts froids en Suisse romande fait apparaître: a) une faible variation annuelle de fréquence à deux maxima très peu prononcés en hiver et en été, et b) une variation diurne beaucoup plus accusée avec deux maxima vers 6 h et vers 16 h.

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Summary Chronological studies of the cold fronts in the French part of Switzerland reveal a) a feeble annual variation of frequency with two maxima only weakly pronounced in winter and summer, and b) a much larger diurnal variation with two maxima at 6 h and 16 h.

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Zusammenfassung Ein chronologisches Studium der Kaltfronten in der französischen Schweiz läßt a) eine schwache Jahresschwankung der Frequenz mit zwei nur schwach ausgedrückten Maxima im Winter und im Sommer, und b) eine bedeutend stärkere Tagesschwankung mit Maxima gegen 6 und 16 Uhr erkennen.

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Avec 2 Figures  相似文献   

Ohne Fallgewicht arbeitender Fernauslöser     

Prof. H. Ambühl  Das Gerät ist erhältlich bei Fa. Dr. H. Züllig 《Aquatic Sciences - Research Across Boundaries》1983,45(2):502-504

A device is described which can be used where working equipment has to be instantly activated (i.e. without time delay) under water. The latch with an adjustable spring, on which the instrument is fastened, can be released by jerking on the supporting cable or by suddenly stopping the lowering motion, thereby instantly activating the working equipment.   相似文献   

Computation of spectra of some simple functions using various types of Windows     

Jaroslav Střeštík  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1982,26(2):145-159

Summary In the introductory part of the paper, a method of computing spectra by computer is described, which cuts down the computer time required without using the Fast Fourier Transformation. Windows which can be used to adjust the resultant spectrum are described. The spectra of a constant, a linear function, a sine function, of the superposition of two sine functions and of the superposition of a sine function with a constant and linear function are described in detail and it is demonstrated how these spectra change when different types of windows are used. The suitability of the separate windows for various purposes is discussed. Finally, in the case of the superposition of two sine oscillations it is shown under what conditions the two frequency components can be distinguished.  相似文献   

Duration Magnitude Scale and Site Residuals for Northern Morocco     

Issam Mouayn  Ben Aissa Tadili  Lahsen Aït Brahim  Mohamed Ramdani  Mohamed Limouri  Nacer Jabour 《Pure and Applied Geophysics》2004,161(5-6):1061-1080

— The first empirical duration magnitude (M_D) formula is developed and tested for the Northern Morocco Seismic Network (NMSNET). This relationship is obtained by relating the IGN (Instituto Geografico National, Madrid) body-waves mbLg^IGN to the duration (), and the epicentral distance (), at 25 analogue stations of the NMSNET for 479 earthquakes with 2.5 mb 5.4, from March 1992 to February 2001. M_D estimates are significantly more precise while introducing a correction term for each of these stations, cSta_j. The magnitude for the i^th event (M_D)_i is the mean value of individual M_Dij=–0.14+1.63log₁₀(_ij)+0.031(_ij)+cSta_j. The cSta_j corrections reduce considerably the local site effects which influence the recorded durations and cause stations to either overestimate, or underestimate M_D up to 0.5 magnitude units. Average station M_D residuals (–cSta_j) are found to be independent of the distance from the epicenter to at least 10 degrees. It seems evident that regional geological features in the immediate behavior of stations have a systematic effect on the corresponding obtained residuals: older well-consolidated Precambrian crystalline rocks produce high negative residuals (shorter durations), younger unconsolidated sediments produce high positive residuals (longer durations), whereas, intermediate M_D site residuals appear to be the result of the effect of various factors, principally age and state of consolidation of the bedrock, combined with the local tectonic.  相似文献   

Monitoring coastal evolution and associated littoral hazards of French Guiana shoreline with radar images     

Hervé Trebossen  Benoît Deffontaines  Nicolas Classeau  Jacob Kouame  Jean-Paul Rudant 《Comptes Rendus Geoscience》2005,337(13):1140-1153

This paper aims at illustrating different case examples of monitoring active coastal evolutions using remote sensing synthetic aperture radar images (ERS 1–2 and Envisat) in humid tropical areas. Effectively, the radar satellite images may be acquired under most climate conditions, especially in cloudy tropical areas. As case examples, we studied herein French Guiana shoreline and its fast evolution under the combined influences of sea currents, sediments and swells. We focused on two aspects of French Guiana littoral evolution: (1) sedimentation and erosion processes linked to mud banks displacements around Kourou City, and (2) around Iracoubo village. Lastly, we compared this short-term sedimentation balance with long-term data showing the discrepancies of short- and long-term littoral evolutions on whole French Guiana. To conclude, this work demonstrates the importance of SAR imagery to provide high-quality and high-frequency update geographic information for coastal management and littoral hazards especially in such tropical humid and cloudy areas. To cite this article: H. Trebossen et al., C. R. Geoscience 337 (2005).  相似文献   

Plio-Quaternary extension in the Venezuelan Andes: Mapping from SAR JERS imagery     

Damien Dhont  Guillaume Back  Yves Hervouët 《Tectonophysics》2005,399(1-4):293

The geometry of extensional structures is described for the first time in the active setting of the Venezuelan Andes using remote sensing imagery. We favored the use of a mosaic of Synthetic Aperture Radar (SAR) scenes of the Japanese Earth Resources Satellite-1 (JERS-1) assisted by complementary remote sensing devices (Landsat TM, digital elevation models) and field observations to make a structural analysis at regional scale. Radar images are particularly efficient in the Venezuelan Andes where dense vegetation and frequent cloud covering earlier lent difficulties to remote sensing studies. We focused our analysis in the Valera–Rio Momboy and Bocono faults corner and in the Mucujun area. We show that, in an area where ongoing compression and strike–slip deformations occur, brittle extension can be detected independently from previous knowledge. Extensional structures correspond to elongated tilted blocks with dimension less than 10 km in width. Blocks are bounded by curved faults in plan view, the concavity being turned towards the axial part of the belt. The geometry and kinematics of such structures suggest that syn-orogenic extension started together with initiation of right-lateral strike–slip motion along the Bocono Fault in the Plio-Quaternary.  相似文献   

The future of stochastic and upscaling methods in hydrogeology     

Benoît Nœtinger  Vincent Artus  Ghassem Zargar 《Hydrogeology Journal》2005,13(1):184-201

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