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

(1) Centro de Geofísica de Évora

(2) Departamento de Física, Universidade de Évora

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

Study of a recent large earthquake

Determine a slip model by inverting teleseismic body waves

Confront the obtained model to various independent datasets

I. Objectives

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

I. The Wenchuan earthquake

Wen

chua

nBei

chu

anAna

xia

n

Zipingpu Dam

I. Longmen Shan fault zone

Google Earth image Wanju et al, 2008

Sichuan basin

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

I. Methodology

I. Spatial destribution of seismic stations

I. Results : co-seismic slip distribution

I. Results: rupture propagationTime of

rupture > 90 sRise time ~

30 s

I. Results: horizontal displacement

Observed

Modeled

Projection of upper edge of fault

plane onto the surface

I. Aftershocks distributionData about

aftershocks was taken for the period of 3 month after the main event

3<Mw<73 km<Depth<32 km

I. Results: changes in Coulomb stress produced by the Wenchuan earthquake

Stress increase

Stress release

Δσс = Δτ - μ’Δσn

μ’ = μ(1 - B)

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

I. Conclusions and perspectives

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

II. Objectives

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.

II. Methodology

October 30, 200737,43 N, 121,78 WMw 5.69.2 km depthStrike: 323˚Dip: 87 ˚Rake: -180 ˚

Slip distribution by Margaret Hellweg et al.

II. Alumn Rock earthquake

II. Near-field accelerograms

II. Basic formulas dt

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Thank you for your attention!