Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?

On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long‐lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of ¹⁴C, ²²Na, ²⁶Al, ⁵⁴Mn, ⁵⁷Co, ⁵⁸Co, and ⁶⁰Co, which indicate that the pre‐atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed ²⁶Al activities of the investigated samples, Monte Carlo simulations, and taking into account the ²⁶Al half‐life (0.717 Myr), the cosmic‐ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, ¹⁴C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of ¹⁴C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic ¹³⁷Cs and primordial ⁴⁰K in some of the Chelyabinsk fragments.     

The model of a flat (Euclidean) expansive homogeneous and isotropic relativistic Universe in the light of the Wilkinson Microwave Anisotropy Probe (WMAP) observations

The Wilkinson Microwave Anisotropy Probe (WMAP) confirmed the model of a flat (Euclidean) expansive homogeneous and isotropic relativistic universe with the total zero mass (energy), which describes the properties of our observed expansive homogeneous and isotropic relativistic Universe in the first (linear, Newtonian or classical-mechanical) approximation.     

The computation of the elastic constants of an anisotropic medium from the velocities of body waves

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Dedicated to 90th Birthday of Professor Frantiek Fiala     

Colour schlieren representation of compressional-stress fields with respect to focal zone study

Summary A method of colour schlieren recording of the compressional-stress field gradients, suitable for focal zone study on models, is suggested. The study presents colour schlieren records of the compressional-stress fields in loaded square plates, containing inhomogeneities which give instant quantitative information on these fields. If the inhomogeneity is shaped like Griffith's diagonal slit, good agreement is demonstrated between the experiment and the theoretical calculation of the compressional-stress field in a model.     

Evolutionary stages of the Banská Stiavnica caldera and its post-volcanic structures

The remains of an extensive volcanic apparatus of the Tertiary « subsequent » volcanism have been identified in the ?tiavnické pohoric Mts. in the inner belt of the Carpathians. The volcanic apparatus, of stratovolcanic type, was formed during several stages of andesitic and rhyolitic volcanism with two caldera stages. During the final stage of volcanic activity the central collapsed area was uplifted as a horst, accompanied by the formation of grabens along the periphery of the central updomed area. The fractured zones of the horst periphery, as well as zones bordering separate subsided blocks of the central area became the sites of economic ore mineralization, with the formation of lead, zinc, copper, gold, and silver bearing veins. In the uplifted central block intrusions of diorite and granodiorite in the pre-volcanic basement have been exposed by erosion. Geological, petrographical, and petrochemical criteria, as well as absolute dating indicate direct chronological and genetic relationships between the diorite-granodiorite intrusions and extrusive volcanism.     

Correction of the level of magnification of the SVK vertical seismograph at the seismic station of průhonice (PRU)

Summary Drawing on the results of new measurements of the mechanical parameters of the SVK seismometer No. 5055, the level of magnification of the vertical seismograph used in the past, has been corrected. The amplitudes of the seismic waves from earthquakes in the period 1963–1978 have to be increased by 88% and the station correction for determining the magnitudes of earthquakes decreased by 0.274.     

Amplitude curves ofP waves for the region of central Asia

Summary The amplitude-distance curves of P waves, valid for the region of Central Asia, were derived in the distance range between 13° and 36° using observations of a network of eight Caucasian seismic stations. The curves are characterized by an anomalous increase of amplitudes between 13° and 20° followed by a large decrease of amplitudes in the distance range between 20° and 35°. Both the increase and decrease of amplitudes are interrupted by several local maxima. A comparison of the present amplitude curves with those derived for the regions of South-Eastern Europe and Asia Minor enabled us to correlate the individual local maxima of amplitude curves and to investigate the variation of their position due to the lateral inhomogeneity of the upper mantle structure in Eurasia.A. Tskhakaya deceased in 1970.     

ДИНАМИЧЕСКИЕ ПАРАМЕТРЫ СИЛЬНЫШ ЗЕМЛЕТРЯСЕНИЙ ПО ДАННЫМ ШИРОКОПОЛОСНОЙ ДЛИННОПЕРИОДНОЙ АППАРАТУРЫ

Summary The dynamic focal parameters of a series of strong earthquakes, recorded by the FBV broadband velocigraph at KHC (Kaperské Hory, Czechoslovakia), are estimated. The influence of specific wave pattern features on the estimation accuracy is studied. Polarization analysis is used to demonstrate the complicated interference character even of record portions corresponding to a single teleseismic wave group. The values of the dynamic focal parameters do not depend significantly on the length of the analysed record portions and are sufficiently consistent with those reported by Riznichenko [2]. The possibility of estimating dynamic focal parameters from recording of standard classes B (intermediate band) and C (long-period) seismographs is pointed out.