Beiträge zur angewandten geomorpho-logie. H. Liedtke (Ed.), Zeitschrift für geomorphologie, 1981, supplementband 39. No. of pages: 137 incl. 49 figures     

Jan De Ploey 《地球表面变化过程与地形》1983,8(2):195-195

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Difference between the even and odd 11-year cycles of geomagnetic activity     

Jaroslav Halenka  Reviewer A. Janáčková 《Studia Geophysica et Geodaetica》1983,27(1):46-58

Summary With the aid of 36 monthly and a double 12-month running average, graphs of the smoothed run of geomagnetic activity were constructed from the monthly values of the geomagnetic activity index aa for the period 1868–1978 and they were then used to determine the run of the geomagnetic activity, expressed during a uniform period and devoid of the secular variation of geomagnetic activity, for the individual 11-year cycles Nos 12–20 and the average runs for even and odd cycles, as well as for the whole period of the 9 cycles. The analysis and comparison of the graphs substantiates and renders more accurate the tendency, observed earlier, towards a regular alternation of geomagnetic activity cycles with double and single maxima. Wheareas a saddle-like shape with a maximum in the neighbourhood of the first and third quarter of the cycle is characteristic of the shape of the even cycle, the second maximum being, as a rule, the main one, the odd cycle is characterized by a peak-like shape with the main maximum in the vicinity of the cycle's centre.  相似文献   

Post-drilling destabilization of temperature profile in borehole Yaxcopoil-1, Mexico     

Jan Šafanda  Philipp Heidinger  Helmut Wilhelm  Vladimír Čermák 《Hydrogeology Journal》2007,15(2):423-428

As part of the International Continental Scientific Drilling Program (ICDP), the 1.5-km-deep borehole Yaxcopoil-1, located in the Chixculub meteor impact structure in Mexico, has undergone further study after drilling operations ceased. Temperature logs were repeated ten times at intervals 0.3–0.8, 15, 24 and 34 months after borehole shut-in. The logs bear a distinct signature of transient heat transfer by groundwater flow manifested by a gradual distortion of the linear temperature profile when a cold wave of 0.8–1.6°C amplitude was detected propagating downward from 145 to 312 m at a rate of 4–6 m/month. To understand the nature of this moving anomaly, a 20-day monitoring of the cold wave was carried out at a depth of 307 m that showed further cooling of 0.6°C during the first 16 days of the passage followed by temperature stabilisation. As an explanation of this unusual phenomenon, a theory is proposed, whereby the drilling mud has accumulated within the overlying and cooler highly porous and permeable karstic rocks during the drilling and migrates downward. The observed migration rate suggests a permeability higher than 10^?11 m². This indicates a high vulnerability to contamination of the only freshwater aquifer in the Yucatan region.  相似文献   

Structural evolution of the contact between two Penninic nappes (Zermatt-Saas zone and Combin zone,Western Alps) and implications for the exhumation mechanism and palaeogeography     

Jan Pleuger  Sybille Roller  Jens M. Walter  Ekkehard Jansen  Nikolaus Froitzheim 《International Journal of Earth Sciences》2007,96(2):229-252

The boundary zone between two Penninic nappes, the eclogite-facies to ultrahigh-pressure Zermatt-Saas zone in the footwall and the blueschist-facies Combin zone in the hanging wall, has been interpreted previously as a major normal fault reflecting synorogenic crustal extension. Quartz textures of mylonites from this fault were measured using neutron diffraction. Together with structural field observations, the data allow a refined reconstruction of the kinematic evolution of the Pennine nappes. The main results are: (1) the contact is not a normal fault but a major thrust towards northwest which was only later overprinted by southeast-directed normal faulting; (2) exhumation of the footwall rocks did not occur during crustal extension but during crustal shortening; (3) the Sesia-Dent Blanche nappe system originated from a continental fragment (Cervinia) in the Alpine Tethys ocean, and the Combin zone ophiolites from the ocean basin southeast of Cervinia; (4) out-of-sequence thrusting played a major role in the tectonic evolution of the Penninic nappes. An erratum to this article can be found at  相似文献   

PGE fractionation in seafloor hydrothermal systems: examples from mafic- and ultramafic-hosted hydrothermal fields at the slow-spreading Mid-Atlantic Ridge     

Jan Pašava  Anna Vymazalová  Sven Petersen 《Mineralium Deposita》2007,42(4):423-431

The distribution of platinum group elements (PGEs) in massive sulfides and hematite–magnetite±pyrite assemblages from the recently discovered basalt-hosted Turtle Pits hydrothermal field and in massive sulfides from the ultramafic-hosted Logatchev vent field both on the Mid-Atlantic Ridge was studied and compared to that from selected ancient volcanic-hosted massive sulfide (VHMS) deposits. Cu-rich samples from black smoker chimneys of both vent fields are enriched in Pd and Rh (Pd up to 227 ppb and Rh up to 149 ppb) when compared to hematite–magnetite-rich samples from Turtle Pits (Pd up to 10 ppb, Rh up to 1.9 ppb). A significant positive correlation was established between Cu and Rh in sulfide samples from Turtle Pits. PGE chondrite-normalized patterns (with a positive Rh anomaly and Pd and Au enrichment), Pd/Pt and Pd/Au ratios close to global MORB, and high values of Pd/Ir and Pt/Ir ratios indicate mafic source rock and seawater involvement in the hydrothermal system at Turtle Pits. Similarly shaped PGE chondrite-normalized patterns and high values of Pd/Pt and Pd/Ir ratios in Cu-rich sulfides at Logatchev likely reflect a similar mechanism of PGE enrichment but with involvement of ultramafic source rocks.  相似文献   

Ray propagator matrices in three-dimensional anisotropic inhomogeneous layered media     

Vlastislav &#;ervený  Tijmen Jan Moser 《Geophysical Journal International》2007,168(2):593-604

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A three-dimensional geophysical model of the crust in the Barents Sea region: model construction and basement characterization   总被引：2，自引：0，他引：2  

Oliver Ritzmann  Nils Maercklin  Jan Inge Faleide  Hilmar Bungum  Walter D. Mooney  Shane T. Detweiler 《Geophysical Journal International》2007,170(1):417-435

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Nonlinear plasma wave processes observed in the polar cusp     

Jan Błęcki  Roman Wronowski  Michel Parrot  Sergey P. Savin 《Acta Geophysica》2007,55(4):459-468

We present observations of electric and magnetic field variations from proton (about few Hz) to electron cyclotron frequencies (about few kHz) obtained by STAFF instrument on Cluster satellites during two cusp crossings, at ∼6 R _E altitude, in September 2002. The cusp was identified by the presence of intensive fluxes of counter streaming electrons with low energies and broadband wave activity which is typical for this region. Special attention is given for the interval of measurements when the waveform of the magnetic field fluctuations was taken in this region by CLUSTER satellites. The wave has been processed using the wavelet and bispectral analysis. Results showing the cascade of turbulence and wave-wave interactions are presented in this paper. A three wave process can be responsible for the broadening of the wave spectra in the polar cusp.  相似文献   

The GPS Toolbox ITRF Transformations     

Jan Kouba 《GPS Solutions》2002,5(3):88-90

The GPS Toolbox is dedicated to highlighting algorithms and source code utilized by GPS engineers and scientists. If you have an interesting subroutine or program you would like to share with our readers, please pass it along so that we might continue to bring you this column; e-mail it to us at gps-toolbox@ngs.noaa.gov. To comment on any of the source code discussed here, or to leave a request for a piece of source code you may be looking for, visit our web site at http:/www.ngs.noaa.gov/gps-toolbox. This column is edited by Stephen Hilla, National Geodetic Survey, NOAA, Silver Spring, Maryland, and Mike Craymer, Geodetic Survey Division, Natural Resources Canada, Ottawa, Ontario, Canada. ? 2002 Wiley Periodicals, Inc.  相似文献   

Progress in Carrier Phase Time Transfer   总被引：1，自引：0，他引：1  

Jim Ray  Felicitas Arias  Gérard Petit  Tim Springer  Thomas Schildknecht  Jon Clarke  Jan Johansson 《GPS Solutions》2001,4(4):47-54

The progress of the joint Pilot Project for time transfer, formed by the International GPS Service (IGS) and the Bureal International des Poids et Mesures (BIPM), was recently reviewed. Three notable milestones were set. (1) The IGS will implement, at least in a test mode, an internally realized time scale based on an integration of combined frequency standards within the IGS network. This will eventually become the reference time scale for all IGS clock products (instead of the current GPS broadcast time). (2) A new procedure for combined receiver and satellite clock products will be implemented officially in November 2000. Receiver clocks are an entirely new product of the IGS. (3) The BIPM will coordinate an effort to calibrate all Ashtech Z12-T (and possibly other) receivers suitable for time transfer applications, either differentially or absolutely. Progress reports will be presented publicly in the spring 2001. ? 2001 John Wiley & Sons, Inc.  相似文献