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S eismic wave P ropagation and I maging in C omplex media: a E uropean network Local scale group. Responsable: Martin Mai, ETH Zürich. Speaker: Raoul Madariaga Senior researcher Ecole Normale Supérieure Paris. Earthquake seismology. Fault model. Direct. Inverse. Modelling. Dynamics.
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Seismic wave Propagation and Imaging in Complex media: a European networkLocal scale group Responsable: Martin Mai, ETH Zürich Speaker: Raoul Madariaga Senior researcher Ecole Normale Supérieure Paris
Earthquake seismology Fault model Direct Inverse Modelling Dynamics Rupture propagation model Propagation Kinematics Wave propagation model
Different scales in earthquake dynamics . BB Seismic waves Macroscale (< 0.3 Hz l> 5 km) Hifi Seismic waves Mesoscale (>0.5 Hz l<2 km) Steady state mechanics Microscale vr (non-radiative) (l~ 100 m) This hierarchy of problems was proposed by Kostrov’s
Challenges in macroscale Kinematics : Are inversions realistic? -> Don’t ask! Are they stable? -> Blind Test Dynamics : How do we set up kinematic inversions that are compatible with dynamics ? Both : How to extend the inversions beyond 0.3 Hz, so that they are useful in engineering ? How to interface with GPS, interferometry and geology?
Earthquakes as dynamic shear ruptures Preexisting Fault system in the Mojave desert Epicenter Rupture modelled on the complex fault system determined from Geology, Geodesy and Seismology
Kinematic vs dynamic modelling Wald and Heaton 1994 Peyrat Olsen Madariaga 2001 Landers 28 June 1992
Model B Model E The « smooth » fault model develops supershear shocks Why? Detailed energy balance Two attempts to model the Izmit Earthquake The « rough » fault models produces subshear ruptures Aochi, Fuyama, Madariaga, 2003 Super shear shock
A simple shear crack (earthquake) moving at fast speed vr Local energy balance friction Es = DU - Gc ini Gc DU slip Dc
Mesoscale: Compare a complex fault to a flat one S waves Residual stresses Rupture front Velocity z Stress zx Stresszy Madariaga and Ampuero, AGU 05 Slow rupture
Outlook for Next 2 years • Kinematics: Improvement of wave propagation, • methodology and structure • (Bonnefoy, Oprsal, Tapia) • Kinematics inversion: Compare linear and non- linear techniques. (Holden, Festa) • Dynamic inversion: Do it! Let it become the norm rather • than the exception. (DiCarli, Burjanek) • Mesocale : Understand the generation of high • frequencies and EQ energy balance • Microscale: See Pablo Ampuero’s presentation Earthquake seismology progresses as earthquake recordingand data availability improves