Analysis of a Low Density Meteoroid with Enhanced Sodium     

Jiří Borovička  Pavel Koten  Pavel Spurný  Rostislav Štork 《Earth, Moon, and Planets》2008,102(1-4):485-493

We present an analysis of sporadic meteor number 07406018, observed by image intensified video cameras at two stations, which showed a pronounced deceleration along its trajectory. We have applied the erosion model to analyze simultaneously the deceleration and light curve. We have found that the meteoroid had a low density of about 500 kg m⁻³, consistent with its cometary orbit. The meteoroid structure was, nevertheless, markedly different from the Draconid meteoroids, studied recently with the same model. The size of the constituent grains was larger and the erosion energy was higher than in Draconids. The meteor spectrum was also different from Draconid spectra and showed very bright Na lines. The meteoroid composition was probably different from normal cometary composition.  相似文献   

Velocity model of the Hronov-Poříčí Fault Zone from Rayleigh wave dispersion     

Petr Kolínský  Jan Valenta  Jiří Málek 《Journal of Seismology》2014,18(3):617-635

The Hronov-Po?í?í Fault Zone (HPFZ) is an active tectonic area with regularly occurring shallow earthquakes up to magnitude 5. For their exact locations, at least an average velocity model of the area is needed. A method of measuring local phase velocities of surface waves using the array of stations deployed permanently in the HPFZ is introduced. Seven regional and teleseismic events are selected to represent different backazimuths of propagation. Applicable range of periods is estimated for each event. The coherency of the waves reaching the array is constraining the short period range. The dimension of the array is a limiting factor for the long-periods. A dispersion curve of Rayleigh wave phase velocity measured at the vertical component and characterizing 1D properties of the target area is determined using the seven measurements for the interval from 1 to 40 s. An isometric method is used to invert the determined dispersion curve for shear and longitudinal velocity distribution from the surface to the depth of 65 km.  相似文献   

Kamchatka subduction zone,May 2013: the Mw 8.3 deep earthquake,preceding shallow swarm and numerous deep aftershocks     

Aleš Špičák  Jiří Vaněk 《Studia Geophysica et Geodaetica》2014,58(1):76-83

A sequence of 98 teleseismically recorded earthquakes occurred off the east coast of Kamchatka at depths between 10-90 km around latitude 52.5°N and longitude 160°E on May 16–23, 2013. The swarm occurred along the northern limit of the rupture area of the 1952 M_w 9.0 great Kamchatka earthquake, the fifth largest earthquake in the history of seismic observations. On May 24, 2013 the strongest deep earthquake ever recorded of M_w 8.3 occurred beneath the Sea of Okhotsk at a depth of 610 km in the Pacific slab of the Kamchatka subduction zone, becoming the northernmost deep earthquake in the region. The deep M_w 8.3 earthquake occurred down-dip of the shallow swarm in a transition zone between the southern deep and northern shallow segments of the Pacific slab. Several deep aftershocks followed, covering a large, laterally elongated part of the slab. We suppose that the two described earthquake sequences, the May 16–23 shallow earthquake swarm and the May 24–28 deep mainshock-aftershock series, represent a single tectonic event in the Pacific slab having distinct properties at different depth levels. A low-angle underthrusting of the shallow part of the slab recorded by the shallow earthquake swarm activated the deep part; this process induced the deep mainshock-aftershock series only three days after the swarm. The domain of the subducting slab activated by the May 2013 earthquake occurrence was extraordinarily large both down-dip and along-strike.  相似文献   

Six-degree-of-freedom near-source seismic motions I: rotation-to-translation relations and synthetic examples     

Johana Brokešová  Jiří Málek 《Journal of Seismology》2015,19(2):491-509

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Dispersion of Love waves from the 2010 Efpalio earthquake in the Corinth Gulf region,Greece     

Oldřich Novotný  Jiří Vackář  Efthimios Sokos 《Journal of Seismology》2015,19(3):801-806

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An Andean type Palaeozoic convergence in the Bohemian Massif     

Karel Schulmann  Jiří Konopásek  Vojtĕch Janoušek  Ondrej Lexa  Jean-Marc Lardeaux  Jean-Bernard Edel  Pavla Štípská  Stanislav Ulrich 《Comptes Rendus Geoscience》2009,341(2-3):266-286

The geological inventory of the Variscan Bohemian Massif can be summarized as a result of Early Devonian subduction of the Saxothuringian ocean of unknown size underneath the eastern continental plate represented by the present-day Teplá-Barrandian and Moldanubian domains. During mid-Devonian, the Saxothuringian passive margin sequences and relics of Ordovician oceanic crust have been obducted over the Saxothuringian basement in conjunction with extrusion of the Teplá-Barrandian middle crust along the so-called Teplá suture zone. This event was connected with the development of the magmatic arc further east, together with a fore-arc basin on the Teplá-Barrandian crust. The back-arc region – the future Moldanubian zone – was affected by lithospheric thinning which marginally affected also the eastern Brunia continental crust. The subduction stage was followed by a collisional event caused by the arrival of the Saxothuringian continental crust that was associated with crustal thickening and the development of the orogenic root system in the magmatic arc and back-arc region of the orogen. The thickening was associated with depression of the Moho and the flux of the Saxothuringian felsic crust into the root area. Originally subhorizontal anisotropy in the root zone was subsequently folded by crustal-scale cusp folds in front of the Brunia backstop. During the Visean, the Brunia continent indented the thickened crustal root, resulting in the root's massive shortening causing vertical extrusion of the orogenic lower crust, which changed to a horizontal viscous channel flow of extruded lower crustal material in the mid- to supra-crustal levels. Hot orogenic lower crustal rocks were extruded: (1) in a narrow channel parallel to the former Teplá suture surface; (2) in the central part of the root zone in the form of large scale antiformal structure; and (3) in form of hot fold nappe over the Brunia promontory, where it produced Barrovian metamorphism and subsequent imbrications of its upper part. The extruded deeper parts of the orogenic root reached the surface, which soon thereafter resulted in the sedimentation of lower-crustal rocks pebbles in the thick foreland Culm basin on the stable part of the Brunia continent. Finally, during the Westfalian, the foreland Culm wedge was involved into imbricated nappe stack together with basement and orogenic channel flow nappes.  相似文献   

Un chronographe électronique pour les mesures séismiques     

Jiří Buben 《Studia Geophysica et Geodaetica》1958,2(2):141-146

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Diskusion einiger modelle der exosphäre auf grundlage der fortpflanzung von pfeifstörungen     

Jiří Mráser 《Studia Geophysica et Geodaetica》1964,8(4):405-408

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Sublethal effects of contamination on the Mediterranean sponge Crambe crambe: metal accumulation and biological responses     

Cebrian E  Martí R  Uriz JM  Turon X 《Marine pollution bulletin》2003,46(10):1273-1284

The effect of low levels of pollution on the growth, reproduction output, morphology and survival of adult sponges and settlers of the sponge Crambe crambe were examined. We transplanted sponges from a control area to a contaminated site and measured the main environmental variables (chemical and physical) of both sites during the study period. Except some punctual differences in particulate organic matter, silicates, nitrates, and water motion, most environmental variables in the water were similar at both sites during the study months. Mainly copper, lead and OM concentrations in the sediment, and water motion were significantly higher at the polluted site and may be implicated in the biological effects observed: decrease in the percentage of specimens with embryos, increase in shape irregularity and decrease in growth rate. Individuals naturally occurring at the polluted site and those transplanted there for four months accumulated ten times more copper than either untouched or transplant controls. Although lead concentration in sediment did not differ between sites, native specimens from the contaminated site accumulated this metal more than untouched controls. Vanadium concentration also tended to increase in the sponges living at or transplanted to the contaminated site but this difference was not significant. C. crambe is a reliable indicator of metal contamination since it accumulates copper, lead and vanadium in high amounts. At the contaminated site, sponge growth, fecundity and survival were inhibited, whereas sponge irregularity ending in sponge fission was promoted. All these effects may compromise the structure and dynamics of the sponge populations in sheltered, metal-contaminated habitats.  相似文献   

Contribution to the experiment of axiomatizing the theory of turbulent diffusion     

Jiří Horák  Reviewer J. Navrátil 《Studia Geophysica et Geodaetica》1978,22(1):86-92

Summary The efforts to axiomatize the theory of turbulent diffusion, founded on the theory of Markovian random processes, are based on the principal logical algebraic aspects of the concept of modelling.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday  相似文献