Bez nadpisu

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Composite source model with fractal subevent size
distribution
Jan Burjánek, Jirí Zahradník Charles University,
Prague
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• time history of modelled event is built from
  time histories of smaller events, so called
  subevents
• subevents are modelled syntheticaly
• effective computation of complete wavefield at
  arbitrary point
• loss of main advantage of EGF - complete path
  information

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• Scaling Laws
• constant stress drop

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w-2 source model
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• Summation method for
• equal sized subevents
• subevents fully fill up mainfault
• summation is provided by method proposed by
  Frankel (1995)

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• Synthetic test
• simple test of the composite model with equal
  sized subevents
• time histories of subevents were modeled by
  filtering white noise

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Self-similar composite model
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Frankel (1991)
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This study
Slope of high frequency fall-off of
displacement spectra is independent of fractal
dimension D !
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prefered triplet

• same as in Irikura (1994), Hartzell et al. (1999)

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• Discrete realization of FSSD
• obtained by method similar to Irikura (1994)

• subevents are placed randomly over the mainfault
  gt we incorporate stochastic element to the method

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Example of one distribution
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Method of summation for non-equal sized subevents
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Synthetic test recomputed using FSSD
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• Non-equal sized subevents produce
• inhomogenous slip distribution

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• Computation subevents
• time histories
• point-source aproximation
• impulse responses of medium are computed by DWN
  method (Bouchon (1981))
• time history of subevent is convolution of an
  impulse response with Brunes function with
  corner frequency

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Simulation of Athens 1999 earthquake

• source model was taken from
• Zahradník and Tselentis (2001)

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• velocity model was taken from
• Novotný et al. (2001)

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Intensities published by NOA
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• Conclusions
• A composite model with FSSD gives more realistic
  results compared to composite model with equal
  subevents
• FSSD generates spatial variation of the slip
  distribution which follows k-2 distribution
• Modelled PGA map explaining main features of the
  macroseismic field