The Morávka meteorite fall: 1. Description of the events and determination of the fireball trajectory and orbit from video records     

J. BOROVI&#x;KA  P. SPURNÝ  P. KALENDA  E. TAGLIAFERRI 《Meteoritics & planetary science》2003,38(7):975-987

Abstract— The Morávka (Czech Republic) meteorite fall occurred on May 6, 2000, 11:52 UT, during the daytime. Six H5–6 ordinary chondrites with a total mass of 1.4 kg were recovered. The corresponding fireball was witnessed by thousands of people and also videotaped by 3 casual witnesses. Sonic booms were recorded by 16 seismic stations in the Czech Republic and Poland and by one infrasonic station in Germany. A total of 2.5% of the fireball eyewitnesses reported electrophonic sounds. Satellites in Earth orbit detected part of the fireball light curve. In this first paper from a series of 4 papers devoted to the Morávka meteorite fall, we describe the circumstances of the fall and determine the fireball trajectory and orbit from calibrated video records. Morávka becomes one of only 6 meteorites with a known orbit. The slope of the trajectory was 20.4° to the horizontal, the initial velocity was 22.5 km/s, and the terminal height of the fireball was 21 km. The semimajor axis of the orbit was 1.85 AU, the perihelion distance was 0.982 AU, and the inclination was 32.2°. The fireball reached an absolute visual magnitude of ?20 at a height of 33 km.  相似文献   

Interferometric observations of HCN and CN towards carbon stars     

M. Lindqvist  R. Lucas  H. Olofsson  A. Omont  K. Eriksson  B. Gustafsson 《Astrophysics and Space Science》1995,224(1-2):501-502

Using the IRAM interferometer we have observed four carbon stars (U Cam, CIT6, Y CVn, IRC+40540) in the HCN(J=1 0) and CN(N=1 0) lines. Here we present some results for CIT6 and U Cam.  相似文献   

Precambrian fluvial deposits: Enigmatic palaeohydrological data from the c. 2–1.9 Ga Waterberg Group, South Africa     

Patrick G. Eriksson  Adam J. Bumby  Jacobus J. Brümer  Markus van der Neut 《Sedimentary Geology》2006,190(1-4):25-46

Precambrian fluvial systems, lacking the influence of rooted vegetation, probably were characterised by flashy surface runoff, low bank stability, broad channels with abundant bedload, and faster rates of channel migration; consequently, a braided fluvial style is generally accepted. Pre-vegetational braided river systems, active under highly variable palaeoclimatic conditions, may have been more widespread than are modern, ephemeral dry-land braided systems. Aeolian deflation of fine fluvial detritus does not appear to have been prevalent. With the onset of large cratons by the Neoarchaean–Palaeoproterozoic, very large, perennial braided river systems became typical. The c. 2.06–1.88 Ga Waterberg Group, preserved within a Main and a smaller Middelburg basin on the Kaapvaal craton, was deposited largely by alluvial/braided-fluvial and subordinate palaeo-desert environments, within fault-bounded, possibly pull-apart type depositories.

Palaeohydrological data obtained from earlier work in the Middelburg basin (Wilgerivier Formation) are compared to such data derived from the correlated Blouberg Formation, situated along the NE margin of the Main basin. Within the preserved Blouberg depository, palaeohydrological parameters estimated from clast size and cross-bed set thickness data, exhibit rational changes in their values, either in a down-palaeocurrent direction, or from inferred basin margin to palaeo-basin centre. In both the Wilgerivier and Blouberg Formations, calculated palaeoslope values (derived from two separate formulae) plot within the gap separating typical alluvial fan gradients from those which characterise rivers (cf. [Blair, T.C., McPherson, J.G., 1994. Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages. J. Sediment. Res. A64, 450–489.]). Although it may be argued that such data support possibly unique fluvial styles within the Precambrian, perhaps related to a combination of major global-scale tectono-thermal and atmospheric–palaeoclimatic events, a simpler explanation of these apparently enigmatic palaeoslope values may be pertinent. Of the two possible palaeohydrological formulae for calculating palaeoslope, one provides results close to typical fluvial gradients; the other formula relies on preserved channel-width data. We suggest that the latter will not be reliable due to problematic preservation of original channel-widths within an active braided fluvial system. We thus find no unequivocal support for a unique fluvial style for the Precambrian, beyond that generally accepted for that period and discussed briefly in the first paragraph.  相似文献   

Andrew Miall: A short overview of a lifetime''s contribution to sedimentary endeavour     

Patrick G. Eriksson  Octavian Catuneanu   《Sedimentary Geology》2006,190(1-4):7-11

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The economic mineral potential of the mid-Proterozoic Waterberg Group, northwestern Kaapvaal craton, South Africa     

P. G. Eriksson  B. F. F. Reczko  C. C. Callaghan 《Mineralium Deposita》1997,32(4):401-409

The 1900–1700 Ma Waterberg Group in the main Waterberg fault-bounded basin consists of dominantly coarse siliciclastic red beds with minor volcanic rocks. The sedimentary rocks were deposited mainly by alluvial fans, fluvial braidplains and transgressive shallow marine environments, with lesser lacustrine and aeolian settings. Uplifted, largely granitic source areas were located along the Thabazimbi-Murchison lineament (TML) fault system in the south, and along the Palala shear zone in the northeast. Palaeoplacer titanomagnetite-ilmenite-zircon heavy mineral deposits, best developed in the Cleremont Formation in the centre of the basin, reflect initial fluvial reworking and subsequent littoral marine concentration. Coarse alluvial cassiterite placer deposits are found in the Gatkop area in the southwest of the basin, and appear to have been derived from stanniferous Bushveld Complex lithologies south of the TML. Hydrothermal zinc and U-Cu mineralisation in the Alma lithologies in the same area appears to be related to the TML fault system. Small manganese deposits and anomalous tungsten values occur in the south of the basin, where they are again closely spatially associated with the TML. Copper-barium mineralisation is found associated with dolerite dykes, and in stratigraphically controlled, inferred syngenetic settings. The most interesting of these apparently syngenetic occurrences is found within green coloured reduced mudrocks and inferred volcanic rocks, at an unconformity developed within the overall red bed sequence of the Waterberg Group, adjacent to the TML in the southwest of the basin. The most important potential mineralisation in the main Waterberg basin thus encompasses shoreline placer Ti and the possibility of substantial sediment-hosted copper deposits. Received: 31 May 1996 / Accepted: 17 February 1997  相似文献   

Atlantic sources of the Arctic Ocean surface and halocline waters   总被引：8，自引：0，他引：8  

Bert Rudels  E. Peter Jones  Ursula Schauer  Patrick Eriksson 《Polar research》2004,23(2):181-208

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Distribution and relative density of cetaceans in the Hauraki Gulf,New Zealand     

SL Dwyer  DM Clement  MDM Pawley  KA Stockin 《新西兰海洋与淡水研究杂志》2016,50(3):457-480

Understanding species distributions, and how they change in space and time, is vital when prioritising conservation or management initiatives. We assessed the distribution and density patterns of common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus) and Bryde’s whales (Balaenoptera edeni) in the Hauraki Gulf, New Zealand. Dedicated boat-based surveys were conducted in the inner Hauraki Gulf (IHG) and off Great Barrier Island (GBI) during 2010–2012. Generalised linear models were used to investigate temporal changes in relative densities and kernel density estimation was implemented to examine spatial trends. Common dolphins were widely distributed during all seasons, with higher densities observed during winter and spring in the IHG but during autumn off GBI. There was inter-annual variation in Bryde’s whale distribution, with high densities recorded off GBI in 2011. Bottlenose dolphins were infrequently sighted in the IHG but regularly encountered off GBI, with the highest densities during spring and summer.  相似文献   

ON THE ABSORPTION-DISPERSION CHARACTERISTICS OF CHANNEL WAVES PROPAGATING IN COAL SEAMS OF VARYING THICKNESS1     

M. DOBR KA 《Geophysical Prospecting》1988,36(3):318-331

The WKB-method is used for the derivation of both the complex dispersion relation and displacement functions for Love channel-waves that propagate in a coal seam of varying thickness. The constant Q-model is used to describe the anelastic friction. With numerical solutions of the absorption-dispersion relation, the influence of thickness changes on the phase velocity and absorption coefficient of Love seam-waves is analysed at various frequencies. It is shown that the changes in the seam thickness can be optimally detected around the average Airy-phase frequency. An equivalence is pointed out between the wave guide structures: homogeneous with varying seam thickness and horizontally inhomogeneous with constant seam thickness.  相似文献   

Airfreight: Geographical patterns and economics. Forecasting models with an example from Finland     

Eriksson  Gösta A. 《GeoJournal》1986,12(3):305-316

In my paper I will try to give some geographical and economical aspects on the recent development of airfreight.Some models for forecasting will be presented, especially three made by (i) DOUGLAS Aircraft's RD; (ii) IATA Freight Traffic Forecasts and (iii) A trend model modified in my department. These three models will be applied and compared with special respect to Finnish airfreights during the 80's.  相似文献   

LOVE SEAM-WAVES IN A HORIZONTALLY INHOMOGENEOUS THREE-LAYERED MEDIUM*     

M. DOBR KA 《Geophysical Prospecting》1987,35(5):502-516

Using the WKBJ-method the absorption-dispersion relation and the amplitude functions are derived for Love seam-waves that propagate in a horizontally inhomogeneous three-layered medium. To describe the anelastic friction the constant Q-model is applied. The inhomogeneity that appears in either the elastic moduli or quality factors is assumed to remain weak in the coal as well as in the adjacent layers, which are assumed to have different material properties (asymmetric channel). Using numerical solutions of the dispersion relation, it is shown that the weak horizontal inhomogeneities can be optimally detected using channel-wave constituents of a frequency near to the Airy frequency while inhomogeneities of the adjacent rock can only be detected at frequencies close to, but higher than, the cut-off frequency.  相似文献