HR: 09:15h
AN: S11E-06    [Abstracts]
TI: Determination of the 8ø discontinuity beneath the major tectonic units of Central Europe from regional seismicity in Europe and northern Africa
AU: NITA, B
EM: blankan@igf.edu.pl
AF: Institute of Geophysics Polish Academy of Sciences, Ks. Janusza 64, Warsaw, 01-452 Poland
AU: * PERCHUC, E
EM: per@igf.edu.pl
AF: Institute of Geophysics Polish Academy of Sciences, Ks. Janusza 64, Warsaw, 01-452 Poland
AU: THYBO, H
EM: thybo@geol.ku.dk
AF: University of Copenhagen, Oster Voldgade 10, Copenhagen, DK-1350 Denmark
AU: MAGUIRE, P
EM: pkm@le.ac.uk
AF: University of Leicester, University Road, Leicester, LE1 7RH United Kingdom
AU: DENTON, P
EM: pdt@leicester.ac.uk
AF: University of Leicester, University Road, Leicester, LE1 7RH United Kingdom
AB: We evaluate the existence and the depth of the '8ø discontinuity' beneath the Alpine orogen using the natural seismicity of Europe and northern Africa as well as events induced by mining activity. For this analysis, the regional events (1) must have epicenters further than 1000 km from the structure being imaged, and (2) the magnitude of body waves must be higher than 4.0 to obtain a favourable signal to noise ratio. The events satisfying the above conditions have epicentres in Algeria, Spain, Bulgaria, Greece and in the Lubin Copper Basin in Poland. The last region is characterised by high seismicity resulting from mining activity. We base our analysis on P-wave traveltime residuals compared to the general iasp91 model. The 8ø discontinuity seems to be attributed to the observed P-wave traveltime delays at epicentral distances around 800 km. The analysis of events from the Lubin Coper Basin and the events from other regions mentioned above, gives P-wave delays of 3 s at the Alpine stations in comparison with stations in the Variscan areas to further north. We attribute this variation in travel time to the difference between 'fast' and 'slow' uppermost mantle structures in Europe.
DE: 7218 Lithosphere and upper mantle
DE: 3025 Marine seismics (0935)
DE: 1734 Seismology
DE: 1645 Solid Earth
SC: Seismology [S]
MN: 2004 AGU Fall Meeting