震后快速钻探:历史、现状与未来

大地震发生后立即在断层带上进行钻探可以帮助我们获取更多的地震信息,尤其是可获得决定断层动态破裂的摩擦水平和强度,观测断层的愈合过程及可能触发余震的应力变化,并可获取控制破裂过程的重要的物理和化学属性。在2008年11月由国际大陆科学钻探项目（ICDP）和南加州地震中心（SCEC）联合在日本东京举办的为期3天的“震后快速钻探：历史、现状与未来”研讨会上,     

Analyse des Standards de L'U.S.G.S. : GXR-1 a GXR-6 par Activation Neutronique et Fluorescence X

Six roches standards de I'USGS : GXR-1 à GXR-6 ont été analysées par activation neutronique instrumentale (INAA) pour le dosage de 17 éléments traces et par fluorescence X (XRF) pour les autres éléments difficiles à doser par activation neutronique. Les travaux précédemment publiés par Gladney et al. ont été pris comme référence en particulier les valeurs recommandées (R.V.) qui sont généralement en bon accord avec nos résultats. Quelques remarques et corrections sont proposées pour expliquer certaines disparités.
Six United States Geological Survey's (USGS) Geochemical Exploration References Samples (GXR) have been analyzed by instrumental neutron activation analysis (INAA) for the determination of seventeen trace elements and by X-ray fluorescence spectrometry (XRFS) for other trace elements difficult to determine by INAA. Our results compare favourably with the values recommended by E.S. Gladney et al. Some suggestions and corrections are proposed to explain some discrepancies.     

Non-linear channel–shoal dynamics in long tidal embayments

The dynamics of finite-amplitude bed forms in a tidal channel is studied with the use of an idealized morphodynamic model. The latter is based on depth-averaged equations for the tidal flow over a sandy bottom. The model considers phenomena on spatial scales of the order of the tidal excursion length. Transport of sediment mainly takes place as suspended load. The reference state of this model is characterized by a spatially uniform M₂ tidal current over a fixed horizontal bed. The temporal evolution of deviations from this reference state is governed by amplitude equations: these are a set of non-linear equations that describe the temporal evolution of bed forms. These equations are used to obtain new morphodynamic equilibria which may be either static or time-periodic. Several of these bottom profiles show strong similarity with the tidal bars that are observed in natural estuaries. The dependence of the equilibrium solutions on the value of bottom friction and channel width is investigated systematically. For narrow channels (width small compared to the tidal excursion length) stable static equilibria exist if bottom friction is slightly larger than r_cr. For channel widths more comparable to the tidal excursion length, multiple stable steady states may exist for bottom friction parameter values below r_cr. Regardless of channel width, stable time-periodic equilibria seem to emerge as the bottom friction is increased.Responsible Editor: Jens Kappenberg     

Plasma Heating by Forced Magnetic Reconnection

A model of forced magnetic reconnection in a force-free magnetic field is considered, which allows calculation of the magnetic energy release during the current sheet reconnection. The dependence of this energy on characteristics of the magnetic configuration has been studied, and it was found that the released energy becomes very large when the field is near the marginal tearing stability. A persistent plasma heating provided by ongoing external driving and internal reconnection is also derived. It shows a typical relaxation-type dependence on the driving frequency, with dissipation becoming most efficient when the time-scales of the driving and reconnection are comparable. Possible implications of the obtained results for the problem of solar coronal heating are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modal summation methods for structural dynamic computations

The rate of convergence of the conventional mode superposition method can be significantly improved for systems subjected to relatively low frequency loadings by adding static correction terms to approximate the contribution of higher modes neglected by the use of a truncated eigenbasis. Two computational variants of the classical mode-acceleration method are developed for that purpose. It is recommended that the pseudo-static displacement correction vector should be computed from an expansion of the flexibility matrix in terms of the retained eigenvectors for actual computer implementation.     

Die Entdeckung eines neuen Asteroiden (1988BJ) vom “Hungaria”-Typ

During an observational program of asteroids at the observatory of Haute Provence (France) an asteroid of 17^th magnitude was discovered on 22^nd January 1988 (Elst 1988). Further observations at the European Southern Observatory (ESO) and a preliminary determination of an orbit revealed that it belongs to the “Hungaria” family.     

Experimental petrology of alkalic lavas: constraints on cotectics of multiple saturation in natural basic liquids

Experimental study of natural alkalic lava compositions at low pressures (pO₂QFM) reveals that crystallization of primitive lavas often occurs in the sequence olivine, plagioclase, clinopyroxene, nepheline without obvious reaction relation. Pseudoternary liquidus projections of multiply saturated liquids coexisting with plagioclase (±olivine±clinopyroxene±nepheline) have been prepared to facilitate graphical analysis of the evolution of lava compositions during hypabyssal cooling. Use of (TiAl₂)(MgSi₂)_–1 and Fe³⁺ (Al)_–1 exchange components is a key aspect of the projection procedure which is succesful in reducing a wide range of compositions to a systematic graphical representation. These projections, and the experiments on which they are based, show that low pressure fractionation plays a significant role in the petrogenesis of many alkalic lava suites from both continental and oceanic settings. However, the role of polybaric fractionation is more evident in the major element chemistry of these lava suites than in many tholeiitic suites of comparable extent. For example, the lavas of Karisimbi, East Africa, show a range of compositions reflecting a polybaric petrogenesis from primitive picrites at 1360° C/18 kb and leading to advanced low pressure differentiates. Evolved leucite-bearing potassic members of this and other suites may be treated in a nepheline-diopside-kspar (+olivine+leucite) projection. Compositional curvature on the plagioclase+clinopyroxene+olivine+leucite cotectic offers a mechanism to explain resorption of plagioclase in alkalic groundmass assemblages and the incompatibility of albite and leucite. This projection is useful for evaluating the extent of assimilation of the alkalic portions of crustal granulites. Assimilation appears to have played some role in the advanced differentiates from Karisimbi.     

Über Flysch und Molasse im Allgäu

Ohne Zusammenfassung     

The suitability of apatite as an age indicator by the uranium-lead isotope method

Experimental data obtained for 14 samples from the granitic terrain surrounding the Barberton Mountain Land in the Republic of South Africa is used to demonstrate that the common accessory mineral, apatite, is suitable for age measurements by the U-Pb isotope method and may in many cases be a more reliable age indicator than the co-existing zircon. The ages calculated for apatite separated from the granitic rocks are in most cases concordant or nearly so (the biggest difference between two uranium-lead ages exhibited being less than 7%); while the ages calculated for co-existing zircon are mostly grossly disconcordant. It is proposed that the theoretical explanation for this observation is found in the crystal chemical stability of the apatite structure as compared to that of zircon. Zircon is probably much more susceptible to loss of members of the U-Pb decay system especially when metamict.     

Revealing the energy sources of alternating intensity regimes of the evolving Alberto tropical cyclone using microwave satellite sensing data

The trajectory characteristics and the intensity evolution of the Alberto tropical cyclone (TC) in the integral water-vapor field are analyzed in detail using a software-algorithmic complex designed for constructing highly detailed global radio-thermal fields of the ocean-atmosphere system based on microwave satellite measurements. This complex was developed by the authors earlier and allows one to obtain global animated radio-thermal fields with a time step of 1.5 h and a spatial resolution of 0.2°. Special attention is paid to the problem of revealing the energy sources of three consecutive intensifications of this TC. The analysis of satellite data with the use of the animation method developed by the authors shows for the first time that these sources are regions with an increased (exceeding the critical level) integral water-vapor content located in different geographical areas lying along the complex trajectory of the TC with a variable intensity. The first region was located in the equatorial intertropical convergence zone, the second was located above the Gulf Stream water area, and the third resided in the area affected by the Azores High.