Map of isoseismals of the main Friuli earthquake of 6 May 1976     

V. Kárník  D. Procházková  Z. Schenková  L. Ruprechtová  A. Dudek  J. Drimmel  E. Schmedes  G. Leydecker  J. P. Rothé  B. Guterch  H. Lewandowska  D. Mayer-Rosa  D. Cvijanović  V. Kuk  F. Giorgetti  G. Grünthal  E. Hurtig 《Pure and Applied Geophysics》1978,116(6):1307-1313

Summary The isoseismal map of the North-Italian earthquake of 6 May 1976 was compiled using the contributions of the European countries lying within the shaken area. The characteristic feature of the macroseismic field is discussed.  相似文献   

³⁹Ar-⁴⁰Ar ages of samples from the Apollo 17 station 7 boulder and implications for its formation     

A. Stettler  P. Eberhardt  J. Geiss  N. Grögler 《Earth and Planetary Science Letters》1974,23(3):453-461

³⁹Ar-⁴⁰Ar ages and³⁷Ar-³⁸Ar exposure ages of samples representing four different lithologies of the Apollo 17 station 7 boulder were measured. The age of the dark veinlet material77015of3.98 ± 0.04AE is interpreted as representing the time of intrusion of this veinlet into the 77215 clast. The data obtained so far indicate that the vesicular basalt 77135 formed 100–200 m.y. later. However, this has to be confirmed by³⁹Ar-⁴⁰Ar investigations on separated mineral and/or grain-size fractions. A small clast enclosed in the 77135 basalt gives a well-defined high temperature age of3.99 ± 0.02AE. A sample of the noritic clast 77215 gave4.04 ± 0.03AE, the highest age found so far in this boulder. The³⁹Ar-⁴⁰Ar ages obtained are in agreement with the age relationships deduced from the stratigraphic evidence.Taking into account the shielding by the boulder itself, an average³⁷Ar-³⁸Ar exposure age of(27.5 ± 2.5)m.y. is obtained for the samples collected from the boulder.  相似文献   

Intermittent Surface Renewals and Methane Hotspots in Natural Peatlands     

Zorzetto  Enrico  Peltola  Olli  Grönholm  Tiia  Katul  Gabriel G. 《Boundary-Layer Meteorology》2021,180(3):407-433

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A RAM-economizing domain decomposition technique for regional high-resolution groundwater simulation     

W.?Gr?sleEmail author  W.?Kessels 《Hydrogeology Journal》2003,11(2):304-310

A major limitation of the use of high-resolution groundwater models on a regional scale for resource management by water companies is the excessive RAM requirements of such models which surpass the capacity of today's PCs. A strategy is presented to overcome this problem by using overlapping domain decomposition techniques. Furthermore, because very long computing time is the bottleneck for the practical use of this technique for large groundwater models, an analysis is also presented of a number of methods implemented to increase calculation performance. The approach presented here is characterized by a fairly simple structure that represents a generalized relaxation algorithm. It can be adapted for use with finite element as well as with finite difference methods. Electronic Publication  相似文献   

The meta-igneous granulite xenoliths from Kerguelen Archipelago: evidence of a continent nucleation in an oceanic setting   总被引：1，自引：1，他引：0  

Michel Grégoire  Jean Yves Cottin  André Giret  Nadine Mattielli  Dominique Weis 《Contributions to Mineralogy and Petrology》1998,133(3):259-283

Xenoliths of meta-igneous origin occur as one of the two main types of ultramafic and mafic xenoliths entrained by alkaline lavas of the Kerguelen islands. These are designated type II xenoliths and are subdivided into three mineralogical groups. Subtype IIa and IIc xenoliths are interpreted as crystallisation products of basaltic melts that were emplaced near the crust-mantle boundary during the early tholeiitic–transitional magmatic activity of the Kerguelen islands. Younger magmatism became more alkaline and subtype IIb xenoliths were formed as high-pressure alkaline cumulates related to the last alkaline volcanic stage. Subsequently, the plagioclase-bearing type II rocks have been re-equilibrated under granulite facies conditions. This addition of mafic material around the crust-mantle boundary is consistent with seismic evidence for crustal thickening to 14–20 km. Calculated compressional seismic velocities (Vp) for the basic granulites are consistent with the range of observed Vp in the low-velocity region underlying the oceanic crust. Such growth in the thickness of the oceanic crust may be caused by intrusion of basalts at different levels in the lithosphere and may provide the heat responsible for granulitic metamorphism in the oceanic setting. This study suggests that basic granulites can account for the observed seismic characteristics of oceanic plateaux and can be important components of Kerguelen oceanic lithosphere where there has been large-scale magma production. Moreover we speculate that the Kerguelen islands and perhaps the surrounding plateau represent a continental nucleation process. Received: 30 September 1997 / Accepted: 17 June 1998  相似文献   

Cleavage mechanism and surface chemical characterization of phengitic Muscovite and Muscovite as constrained by X-Ray Photoelectron Spectroscopy     

Giuseppe G. Biino  Pierangelo Gröning 《Physics and Chemistry of Minerals》1998,25(2):168-181

Freshly cleaved (001) natural muscovite was chemically characterized by X-ray Photoelectron Spectroscopy (XPS). The investigated muscovite crystals have composition ranging from pure end member to phengitic muscovite. XPS provides experimental evidence that the chemical composition of the near-surface region differs from the bulk. This difference is not due to analytical problems, but to extreme surface sensitivity of XPS. Depth profiling was also carried out after tilting of 60° or 70° of the sample along an axis perpendicular to [001]. After tilting of phengitic muscovite, the concentration of Al increases and of K decreases, and therefore Al is the topmost monolayer. Repulsion between the octahedral and tetrahedral sheets, stacking faults or more probably interlayered phases (gibbsite-like) are responsible for the cleavage. Possible perturbations of surface chemistry due to X-ray radiation and Ar⁺ ion sputtering have also been investigated. X-ray radiation is negligeable, but Ar⁺ ion sputtering introduces important structural modifications, perturbation of the chemical environment of elements and minor chemical variations. Received: 13 November 1996 / Revised, accepted: 21 March 1997  相似文献   

Seismic hazard assessment for low-seismicity areas — Case study: Northern Germany     

Gottfried Grünthal  Christian Bosse 《Natural Hazards》1996,14(2-3):127-139

The problem of assessing seismic hazard in low-seismicity areas becomes obvious in many practical applications. A typical low-seismicity area, which experienced damaging earthquakes in historical times, is the North German Plain, for which a case study is presented. It is shown how seismic hazard assessments are influenced by different interpretations of historical key earthquakes, changes in b-value as well as variations of the upper bound magnitude assumed for the seismic source regions. The latter strongly influences the hazard results in the case of very low b-values for long return periods.  相似文献   

Pollen diagram from the Nebraska Sandhills and the age of the dunes     

H.E. Wright  J.C. Almendinger  J. Grüger 《Quaternary Research》1985,24(1):115-120

Radiocarbon dates of organic alluvium beneath as much as 40 m of dune sand along the Dismal River have led to the suggestion that the Nebraska Sandhills date from the Holocene rather than the last glacial period. On the other hand, the basal layers of lake and marsh deposits in interdune depressions at three localities date in the range of 9000 to 12,000 yr B.P., implying a pre-Holocene age for the sand dunes. A pollen diagram for one of these sites, Swan Lake, indicates prairie vegetation throughout the last 9000 yr, with no suggestion that the landscape was barren enough to permit the shaping of the massive dunes characterizing the area. Sand was not transported across the site during the Holocene, either during the marsh phase, which lasted until 3700 yr B.P., or during the subsequent lake phase. The sand that buries the alluvium along the Dismal River may represent only local eolian activity, or it may indicate that the younger of the two main dune series identified by H. T. U. Smith (1965, Journal of Geology73, 557–578) is Holocene in age, and the older one Late Wisconsin in age.  相似文献   

Chi-square regression for seismic strength parameter relations, and their uncertainties, with applications to an M w based earthquake catalogue for central, northern and northwestern Europe   总被引：2，自引：1，他引：2  

D. Stromeyer  G. Grünthal  R. Wahlström 《Journal of Seismology》2004,8(1):143-153

A generalized chi-square regression approach to establishempirical relations between different types of seismic strengthparameters with uncertainties in all input data is presented anddiscussed in comparison with standard least-squares techniques.The chi-square technique can consider errors of individual entriesbut can also be applied when errors are not exactly known and onlyweaker quantitative constraints can be made. It can preserve thesymmetry of the derived relations and is preferred for complexregression models. Results for three types of regression modelsare presented for (1) a linear relation between M _Sand m _bfor events in the North Atlantic Ocean; (2) a quadratic relationbetween M _w and M _L forevents in central Europe; (3) linearrelations between M _L and I ₀,with logarithmic dependency ofthe focal depth, for several regions in central and northernEurope.  相似文献   

The motion of charged dust particles in interplanetary space—I. The zodiacal dust cloud     

G.E. Morfill  E. Grün 《Planetary and Space Science》1979,27(10):1269-1282

The problem of electromagnetic perturbations of charged dust particle orbits in interplanetary space has been re-examined in the light of our better understanding of the large scale spatial and temporal interplanetary plasma and field topology. Using both analytical and numerical solutions for particle propagation it was shown that: (1) stochastic variations induced by electromagnetic forces are unimportant for the zodiacal dust cloud except for the lowest masses, (2) systemetic variations in orbit inclinations are unimportant if orbital radii are larger than 10 a.u. This is due to the solar cycle variation in magnetic polarity which tends to cancel out systematic effects, (3) systematic variations in orbital parameters (inclination, longitude of ascending node, longitude of perihel) induced by electromagnetic forces inside 1 a.u. tend to shift the plane of symmetry of the zodiacal dust cloud somewhat towards the solar magnetic equatorial plane, (4) inside 0.3 a.u. there is a possibility that dust particles may enter a region of “magnetically resonant” orbits for some time. Changes in orbit parameters are then correspondingly enhanced, (5) the observed similarity of the plane of symmetry of zodiacal light with the solar equatorial plane may be the effect of the interaction of charged interplanetary dust particles with the interplanetary magnetic field. Numerical orbit calculation of dust particles show that one of the results of this interaction is the rotation of the orbit plane about the solar rotational axis.  相似文献