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26 July 2013 Símon Ólafsson , EERC

Scientific aspects of South Iceland earthquakes. 26 July 2013 Símon Ólafsson , EERC. Outline. Introduction Icelandic Strong Motion Network Estimation of source parameters Ground motion prediction equation (GMPE) Discrete time realization Conclusions. Historical earthquakes in the SISZ.

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26 July 2013 Símon Ólafsson , EERC

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  1. Scientific aspects of South Iceland earthquakes 26 July 2013 SímonÓlafsson, EERC

  2. Outline • Introduction • Icelandic Strong Motion Network • Estimation of source parameters • Ground motion prediction equation (GMPE) • Discrete time realization • Conclusions UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  3. Historicalearthquakesinthe SISZ UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  4. Icelandic Strong Motion Network UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  5. ÁrborgTown Hall: The strong-motion array UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  6. The Árborg Town Hall: Earthquake 29 May 2008, UTM 15:45 UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  7. Internet Site for the European Strong motion Database (ISESD) UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  8. Recent earthquakes in South Iceland • Mw6.0, 25 May 1987 • Mw 6.5, 17 June 2000 • Mw6.5, 21 June 2000 • Mw6.3, 28th May 2008 UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  9. Ground motion model (Stochastic method) UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  10. Selection of S-wave window UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  11. Estimation of parameters Dsstress drop k =R/Qb‘spectral attenuation’ M0 seismic moment Moment magnitude Mw(Hanks-Kanamori): UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  12. Earthquake 28 May 2008 - Parameters ParameterEstimate Units _____________________________________ Mo 3.4×1018 N m Mw 6.26 Fc 0.24Hz r 6.4km k 0.053 s Ds 73.0×104 Pa u 79.4 cm _____________________________________ UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  13. Attenuation of PGA South Iceland June 2000 UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  14. Geometric spreading function d = epicentral distance h = depth parameter D1, D2 and D3are used to set the limits for the different zones of the spreading function UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  15. Derivation of GMPE Parseval theorem: PGA(amax) related to rms-acceleration (arms) with peak factor (p): amax = parms UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  16. Theoretical GMPE UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  17. Attenuation for 29 May 2008 UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  18. Duration estimation • a) Duration based on 90% cumulative energy. The dotted red curve represent mean value +/- one standard deviation (+/-1s). b) The curves represent the duration function of Eqn. 3.10 for different fractions of total cumulative energy (50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% and 90%). UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  19. Ground motion simulation UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  20. Discrete time realizations Time domain equations for sub-filters representing discrete model. UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  21. Conclusions • For the South Iceland earthquakes the near-field attenuation has a high rate of attenuation (R-2) • Ground motion model (GMPE) has to include a geometrical attenuation term to accound for the fast rate of attenuation in the near-field • GMPE based on a physical model can be applied to obtain ground motion parameters and for time series simulation • For realistic simulation of ground motion time sequences a realistic estimate of duration is important. UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  22. UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  23. Introduction • Examine relationship: Modified Mercally Intensity (IMM) vs. g UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  24. UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  25. Estimating parameters • PGA, PGV: Use for example larger og two horizontal component, average of peak values for horizontal UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  26. Intensities map UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

  27. UPStrat MAFA: 3rd General Meeting in Selfoss, July 23-26, 2013

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