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  • Springer Science + Business Media  (2)
  • 1
    Publication Date: 2006-03-01
    Description: The equation of radiative transfer is used to model the transport of seismic energy in 2-D and 3-D acoustic random media. Monte-Carlo solutions of this equation using non-isotropic Born scattering coefficients are compared to three analytical solutions: Markov approximation, radiative transfer theory with isotropic scattering coefficients, and diffusion approximation. Additionally, we compare to finite differences solutions of the full wave equation in 2-D. We find a good correspondence of radiative transfer theory to Markov approximation for the case of multiple forward scattering. The comparison to radiative transfer theory with isotropic scattering coefficients, a model frequently used in data analysis, demonstrates that in the case of forward scattering the isotropic scattering model is not better than a diffusion approach. To compare radiative transfer theory with non-isotropic scattering coefficients to finite differences solutions of the full wave equation, the finite source duration and the bandpass filter process as well as the normalization of absolute amplitudes are explicitely taken into account. We find a good coincidence of both theories for scattering parameters, which are realistic for usual Earth crust. The theory correctly describes the unscattered direct wavefront, the envelope broadening caused by multiple forward scattering, as well as the late coda caused by multiple wide angle scattering. For strong scattering, which can be expected for very heterogeneous media such as strato volcanoes, the solutions of radiative transfer differ from the more complete solutions of the full wave equation. ©2006 Birkhäuser Verlag, Basel,
    Print ISSN: 0033-4553
    Electronic ISSN: 1420-9136
    Topics: Geosciences , Physics
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  • 2
    Publication Date: 2009-02-12
    Description: A new network of permanently recording seismic stations in West Saxony has considerably improved detection threshold, location accuracy and depth determination in this seismically active region. Between 2001 and 2007 more than 900 events have been located. Seismicity mainly occurred along a band stretching north-south between Leipzig and Vogtland/NW Bohemia area with local magnitudes ranging between −0.8 and 2.8. Seismicity clearly delineates the Leipzig-Regensburg (L-R) fault zone striking N-S, and the Gera-Jachymov (G-J) fault zone striking roughly NNW-SSE. The hypocentral depths can be divided into two depth ranges, one at depths below 10 km, and a second at less than 10 km depth that only extends S-N from the Vogtland until the crossing between L-R and G-J fault zones. A small earthquake sequence that occurred near Werdau/Zwickau in August 2006 at almost the same epicenters as an earlier sequence 1997/98 seems to confirm this finding: a relative localization of 15 events with the double-difference technique clearly reveals two distinct subclusters at about 6 and 12–14 km depth. With the improved station coverage 33 new fault plane solutions from events along the L-R fault zone north of the swarmquake area could be determined from P-polarities and P/S ratios. They do not differ significantly from solutions in the Vogtland/NW-Bohemia area and are mostly compatible with a N-S oriented fault plane. Strike slip mechanisms with or without a dip slip component dominate. ©2008 Institute of Geophysics of the ASCR, v.v.i
    Print ISSN: 0039-3169
    Electronic ISSN: 1573-1626
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
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