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Zadonina E.O. (1) , Caldeira B. (1,2) , Bezzeghoud M. (1,2), Borges J.F. (1,2)

I. Slip distribution, co-seismic deformation and Coulomb stress change for the 12 May 2008 Wenchuan (China, M w 7.9 ) earthquake II. Influence of model parameters on synthesized high-frequency strong-motion waveforms.

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Zadonina E.O. (1) , Caldeira B. (1,2) , Bezzeghoud M. (1,2), Borges J.F. (1,2)

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  1. I. Slip distribution, co-seismic deformation and Coulomb stress change for the 12 May 2008 Wenchuan (China, Mw7.9) earthquakeII. Influence of model parameters on synthesized high-frequency strong-motion waveforms Zadonina E.O. (1), Caldeira B. (1,2), Bezzeghoud M. (1,2), Borges J.F. (1,2) Centro de Geofísica de Évora Departamento de Física, Universidade de Évora

  2. I. Objectives • Study of a recent large earthquake • Determine a slip model by inverting teleseismic body waves • Confront the obtained model to various independent datasets

  3. I. The Wenchuan earthquake • 12 May 2008 – Wenchuan Earthquake Mw 7.9 (China) • Occurred on the boundary between Longmen Shan and Sichuan basin (31.1˚ N, 103.3˚ E) at the 19 km depth • Claimed 69,000 lives

  4. I. Longmen Shan fault zone Wenchuan Google Earth image Beichuan Anaxian Zipingpu Dam Sichuan basin Wanju et al, 2008

  5. I. Methodology • Preprocessing of teleseismic body waves and determination of source parameters • Inversion of teleseismic body-waves with Kikuchi and Kanamori's algorithm to obtain slip distribution • Modeling of horizontal displacements and Coulomb stress change • Comparison of obtained results with GPS data and aftershocks distribution

  6. I. Spatial destribution of seismic stations

  7. I. Results : co-seismic slip distribution

  8. I. Results: rupture propagation • Time of rupture> 90 s • Rise time ~ 30 s

  9. I. Results: horizontal displacement Modeled Observed Projection of upper edge of fault plane onto the surface

  10. I. Aftershocksdistribution • Data about aftershocks was taken for the period of 3 month after the main event • 3<Mw<7 • 3 km<Depth<32 km

  11. I. Results: changes in Coulomb stress produced by the Wenchuan earthquake Stress increase Δσс=Δτ-μ’Δσn μ’ = μ(1 - B) Stress release

  12. I. Conclusions and perspectives • Obtained horizontal surface displacement not in the strict agreement with observed data • Changes in static Coulomb stress are consistent with aftershock distribution down to a depth of 7 km • Perspective – refining of existing source parameters and slip model; joint inversion of strong motion data and InSAR data

  13. II. Objectives • Synthesize high-frequency near-fault waveforms produced by hypothetical earthquake with certain parameters • Numerically estimate the influence of some of the used parameters – source time function, geometry of a fault plain, variations in velocity model, rupture velocity - on the waveforms • Use obtained knowledge in synthesis of waveforms of real event – The Alum Rock earthquake occurred on October 30, 2007 using the existing slip model of the event and Community Velocity Model SCEC CVM-H 6.2

  14. II. Methodology • 2D/3D elastic finite-difference wave propagation code E3D based on the elastodynamic formulation of the wave equation on a staggered grid • Misfit Criteria for Quantitative Comparison of Seismograms by Miriam Kristeková et al.

  15. II. Alumn Rock earthquake • October 30, 2007 • 37,43 N, 121,78 W • Mw 5.6 • 9.2 km depth • Strike: 323˚ • Dip: 87 ˚ • Rake: -180 ˚ • Slip distribution by Margaret Hellweg et al.

  16. II. Near-field accelerograms

  17. II. Basic formulas

  18. Thank you for your attention!

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