Moment Tensor Inversion of Regional Phases: Application to a Mine Collapse

—?The aim of our study consists of analyzing potentially non-double-couple seismic events recorded at regional distances. In order to define the nature of the seismic source, a moment tensor inversion is carried out as this method is general enough not to initially constrain the source mechanism. In this paper we present an application to a seismic event induced by a mine collapse which occurred near the town of Halle in Germany. Because of its induced nature, many parameters such as the location and geometry of this seismic source are known. This information allows us to test the influence of inadequate propagation modeling on the moment tensor obtained from the inversion. Green's functions have been computed with the reflectivity method in a flat layered medium, using the European model EurID (Du et? al., 1998; Dufumier et al., 1997). From the inversion of P-wave seismograms recorded by the German Regional Seismic Network will, we obtained a source time function which can be decomposed into two subevents. The first one has a large isotropic part and a deviatoric mechanism with near vertical nodal planes. No volume change is observed for the second subevent, but a deviatoric component opposite of the first one. The addition of S-waves does not change the results of the inversion which are stable. Surface waves were not used because of their poor dispersion curves. Based on the moment tensor obtained from these inversions, the physical process at the source is compatible with a large cavity collapse.     

Genetische Probleme der Zinn-Wolfram-Vererzung im Erzgebirge

Zusammenfassung Die Zinnvererzungen im Erzgebirge stehen in engen räumlichen Beziehungen zu den Granitkontakten. Dieses Merkmal wird durch eine strukturelle Rolle der konsolidierten Endokontaktpartien der Granite beim Aufstieg der Erzlösungen erklärt. Die Mineralisationslösungen stammen aus den tieferen Teilen der Erdkruste; die Lagerstätten stehenin einer paragenetischen Stellung zu den Graniten. Die Zinn-Wolfram Mineralisation verlief in mehreren Mineralisationsstadien. In den Quarzgängen konnte eine deutliche innere Gangmetasomatose beobachtet werden, bei der ine ältere Quarzgangfüllung verdrängt wurde. Die symmetrischen Salbänder mancher Mineralien um die Quarzgänge sind durch Verdrängung des Quarzes vom Gangkontakt aus gebildet worden. Die Abschnitte der Quarzgänge mit Feldspäten die den Pegmatiten sehr ähnlich sehen, sind durch Metasomatose nach der Greisenbildung entstanden. Die Granitbildung wurde von extensiven Nebengesteinsumwandlungen begleitet bei der Kalifeldspatbildung (I–II), Albitisierung, Vergreisung, Serizitisierung, Kaolinitisierung, und Hämatitisierung unterschieden werden. Die wichtigsten geologischen und mineralogischen Merkmale der Lagerstätten sind in Tabellen zusammengefaßt.

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The tin-tungsten mineralization in the Kruné hory Mts. /Erzgebirge shows a close spatial association with the granite contacts. This feature is explained by the structural control of solid endocontact part of the granite bodies for the import of postmagmatic solutions. The mineralizing solutions were derived from the deeper parts of the earth's crust, the ore deposits being thus in a paragenetic position to the granites. The tin-tungsten mineralization occurred during an interrupted process of metallization in the course of several stages. In the quartz veins a distinct intravenous metasomatism was observed with the replacement of earlier quartz vein fillings. The symmetrical selvages of some minerals around quartz veins originated by the replacement of quartz from the wall contact. The sections of the quartz veins with felspars resembling very closely the pegmatites were formed by the post-greisen metasomatism of the quartz veins. The emplacement of granites was accompanied by extensive wall- rock alterations of which potash- felspatization (I and II), albitization, greisenization, sericitization, kaolinization and hematitization were distinguished. The main geological and mineralogical features of the deposits are summarized in tables.

     

Evolution of the Green Corona in 1996–2002

We analysed the green-line coronal intensities (530.3 nm, Fexiv), both their time- latitudinal distribution as well as the coronal index of solar activity (CI) over the period 1996–2002. Maximum values of the CI (smoothed) were observed in mid-August 2001, even though the `first' peak was observed in the period January–April 2000. The maximum of the Wolf number occurred in 2000, April – July, and the `second peak' occurred in December 2001–March 2002. Both indices have a similar course in the cycle, but their maxima are shifted by 1.5 year. There was high correlation between CI and Wolf number, the 2800 MHz radio flux, the X-ray 0.1–0.8 nm flux and cosmic-ray flux. The CI values in present cycle 23 are lower than those of the two former solar cycles 21 and 22 by about 1/3. Polar branches, which separated from the principal equatorward branch at mid-latitudes in the cycle minimum, 1996, reached the poles around 2000. The new principal branch for cycle 24 split in 2001, turned over around ±60° in 2002.5 and moves to the equator, where it will end in 2019. Minimum between cycles 23 and 24 will occur around 2007.5, cycle maximum 24 around 2012.5. Poleward branches in cycle 24 will reach the solar poles in 2011.     

Investigation of the electrostatic charging of dust particles in a Paul-trap

Dust particles (glass, tungsten, and nickel) with sizes ranging from 0.25 to 3m were levitated in a Paul-trap and charged by ions or electrons. For ions the particle potential is limited at field strength of about 1×10⁹ V m^–1 by a temperature-dependent discharge mechanism. The particles interaction with 2 to 20 keV electrons always leads to positive surface potentials which can be explained in terms of a decreased absorption of electrons by small particles. Micrometer sized agglomerates were used for the investigation of the electrostatic fragmentation. Fragmentation takes place in a twofold manner: small surface flufl can be removed or the parent particle can be disrupted into smaller agglomerates.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Eddy energy dissipation rate and puff diffusion during calms

The paper considers a puff diffusion in its inertial stage when particle separation obeys the laws of the inertial subrange and depends only on eddy energy dissipation rate . The can be determined in the surface layer by the turbulent kinetic energy equation. Similarity equations connect with diffusion measure .A simple analytical model has been deduced to estimate pollutants diffusion during calms.     

Density and magnetic models of the lithosphere along CELEBRATION 2000 profile CEL01

The paper presents 2D density and magnetic models of the crust and upper mantle along the DSS line profile of the CELEBRATION 2000 project that crosses the most important geological units in Central Europe. These are the Alps-Carpathians-Pannonian (ALCAPA) region, the SE part of the Paleozoic Platform (PLZ), the Trans-European Suture Zone (TESZ) and a fragment of the SW portion of the East European Craton (EEC). The density and magnetic models were constructed on the basis of a 2D model of P-wave velocity converted into density model, geological data as well as geothermal data and the results of integrated geophysical modelling for the lithosphere-asthenosphere boundary.