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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 130 (1989), S. 83-97 
    ISSN: 1420-9136
    Keywords: macroseismic data ; focal mechanism ; circular source ; energy flow ; directivity ; local effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A simple method is presented for the computation of theoretical models of the macroseismic field, approximately valid close to the epicentre of a weak crustal earthquake. It is assumed that the intensity is logarithmically proportional to the energy flux of a complete directS wave. A circular source is used, whose energy-flux directivity is weak and thus simply predictable. The focal mechanism influences the solution through standard far-field double-couple radiation patterns. For the wave propagation in the layered crust the ray method is used, and a simple absorption correction is applied. Conversion coefficients at the earth's surface are included. To speed up repeated computations of the theoretical macroseismic fields for varying focal mechanisms, the ray quantities are computed (and stored) separately. This makes the program fast and simple enough even for routine applications on small microcomputers, whenever observed macroseismic fields, focal mechanisms, and hypocentre locations need joint interpretation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of seismology 2 (1998), S. 337-349 
    ISSN: 1573-157X
    Keywords: crustal propagation ; Discrete Wwavenumber ; Empirical Green's ; rupture propagation ; seismic source ; site effects ; strong
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A damaging earthquake occurred on 14 July 1993 in Patras, Western Greece. The mainshock (local magnitude 5.1) was followed on the same day by two aftershocks of magnitudes 4.4 ML and 3.6 ML, respectively. The strong motion record of the mainshock is studied, based on the teleseismically determined seismic moment and focal mechanism. The Discrete Wavenumber (DW) and Empirical Green's Function (EGF) methods are used. The main conclusion is that the 1993 Patras mainshock had a complex S-wave group mainly due to structural (path and site) effect. However, some effects of the rupture stopping on the peak ground acceleration (0.2 g in the so-called S3 phase) cannot be ruled out. Two values of the source radius are suggested: R = 1.9 and 3.0 km. The strong motion record better agrees with R = 1.9 km. If the latter is true, the stress drop was of the order of 20 MPa, i.e., higher than often reported for comparable events in Western Greece. Regardless of the true source radius, the ratio of stress drops between the mainshock and aftershocks was about 1–2. The aftershock waveforms indicate significant lateral heterogeneities around Patras. Therefore, the ground-motion predictions of strong events in the area will remain highly non-unique until weak events from an immediate neighbourhood of the particular fault are recorded.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Natural hazards 10 (1994), S. 149-170 
    ISSN: 1573-0840
    Keywords: Finite-difference method ; numerical predictions ; site effects ; earthquake ground motions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Weak and strong ground motions were numerically predicted for three stations of the Ashigara Valley test site. The prediction was based on the records from a rock-outcrop station, one weak-motion record from a surface-sediments station, and the standard geotechnical model. The data were provided by the Japanese Working Group on the Effects of Surface Geology as a part of an international experiment. The finite-difference method for SH waves in a 2-D linear viscoelastic medium (a causalQ model) was employed. Comparison with the real records shows that at two stations the predictions fit better than at the third one. Strangely, the two better predictions were for stations situated at larger distances from the reference rock station (one station was on the surface, the other in a borehole). The strong ground motion (the peak acceleration of about 200 cm s−2) was not predicted qualitatively worse than the weak motion (8 cm s−2). A less sophisticated second prediction (not submitted during the experiment), in which we did not attempt to fit the available weak-motion record at the sedimentary station, agrees with the reality significantly better.
    Type of Medium: Electronic Resource
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