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Attenuation Models for High-F Simulations

Attenuation Models for High-F Simulations. Thomas H. Jordan and Xin Song May 2 nd , 2013. Q Models Used in SCEC Simulations. z = 1 km. z = 1 km. z = 1 km. z = 1 km. Hauksson & Shearer (2006) velocity model (bottom-left) is more similar to CVM-S (top-right) than CVM-H (top-left).

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Attenuation Models for High-F Simulations

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  1. Attenuation Models for High-F Simulations Thomas H. Jordan and Xin Song May 2nd, 2013 Song & Jordan

  2. Q Models Used in SCEC Simulations Song & Jordan

  3. z = 1 km z = 1 km z = 1 km z = 1 km Hauksson & Shearer (2006) velocity model (bottom-left) is more similar to CVM-S (top-right) than CVM-H (top-left) Song & Jordan

  4. z = 10 km z = 10 km z = 10 km Hauksson & Shearer (2006) velocity model (bottom-left) is more similar to CVM-S (top-right) than CVM-H (top-left) Song & Jordan

  5. Qs is NOT linearly related to Vs at 1km depth z = 1 km Song & Jordan

  6. Qs is NOT linearly related to Vs at 10km depth Song & Jordan

  7. Song & Jordan

  8. Qs ≈ Qpat 1km depth Qp Qs Song & Jordan

  9. Qs > Qpat 10km depth Qp Qs Song & Jordan

  10. Song & Jordan

  11. ShakeMap Database QS ~ f1 QS ~ f1/2 QS ~ f0 Attenuation shows strong frequency dependence: QS~ fγwhere γ > 0.5 Song & Jordan

  12. ShakeMap Database QS ~ f1 QS ~ f1/2 QS ~ f0 Attenuation shows strong frequency dependence: QS~ fγwhere γ > 0.5 Song & Jordan

  13. ShakeMap Database QS ~ f1 QS ~ f1/2 QS ~ f0 Attenuation shows strong frequency dependence: QS~ fγwhere γ > 0.5 Song & Jordan

  14. H & S shows lower average VSand VP at shallow depths than either CVM-S or CVM-H. Song & Jordan

  15. When corrected to low frequencies using QS ~ f2/3, H & S is in close agreement with QS = 50 VSat depth, but not near the surface (z < 5 km). Song & Jordan

  16. QS = 50 VS Horizontal averages over CyberShake region Song & Jordan

  17. Conclusions • Hauksson & Shearer (2006) velocity modelis more similar to CVM-S than CVM-H over CyberShake region. • Qs is NOT linearly related to Vs • Qs≥ Qp • H & S shows lower average VS and VP at shallow depths than either CVM-S or CVM-H. • Attenuation shows strong frequency dependence: QS ~ fγwhere γ > 0.5. • When corrected to low frequencies using QS ~ f2/3, H & S is in close agreement with QS = 50 VS at depth, but not near the surface (z < 5 km). Song & Jordan

  18. Recommended Q Model • Use depth-dependent QS-VSrelationships given in following tables • Use QS ~ fγwhere γ = 0.7. • Use Qp = 1.9 Qs0.9. Song & Jordan

  19. A(z) from H&S CyberShake Averages (assumes f0 = 4 Hz) Song & Jordan

  20. A(z) from H&S CyberShake Averages (corrected to f = 0.5 Hz assuming QS ~ f0.7) Song & Jordan

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