S eismic wave P ropagation and I maging in C omplex media: a E uropean network

1. Seismic wave Propagation and Imaging in Complex media: a European network Preliminary results of earthquake ground-motion modeling in the Valley of Grenoble, French Alps FRANTISEK GALLOVIC PETER FRANEK Charles University, Prague Comenius University, Bratislava Task Groups: Local Scale, Numerical Methods

2. Grenoble prediction experiment Input: Structural modelandbasic properties of the point (finite-extent) sourceTask: ground motions inside and outside of the Grenoble Valley Its extention (finite-extent source) • Two rupture scenarios (more in near future) • Applicability of “synthetic transfer functions” in scenario studies to account for the basin effects

3. 3D finite-difference (FD) method • staggered-grid displacement-velocity-stress scheme • 4th-order in space, 2nd-order in time • Adjusted FD Approximation technique (Kristek et al. 2002) • Rheology of Generalized Maxwell Body (Kristek and Mozco 2003) • Parallelized by Kristek (on 4CPU approximately 10x faster than on 1CPU)

4. N Computational FD model BEDROCK SOIL Q: 50 m Q:  : 2730 kg/m3

5. grid spacing in finer grid: 30.0 m grid spacing in coarser grid: 90.0 m time step: 0.002 s frequency range: 0.2 – 2.0 Hz Computational FD model

6. Homogeneous Source model • Kinematic model • Strike 120°, Dip 90°, Rake 180° • Fault plane: 9 x 4.5 km2 • Hypocentral depth: 3 km • Boxcar slip velocity function • Constant • Rise time (1.1 sec) • Rupture velocity (2.8 km/s) • Final slip (1.1 m)

7. Homogeneous source model(slip velocity)

8. Heterogeneous Source model • Kinematic model • Strike 120°, Dip 90°, Rake 180° • Fault plane: 9 x 4.5 km2 • Hypocentral depth: 3 km • Brune’s pulse slip velocity function • Constant • Rise time (1.1 sec) • Rupture velocity (2.8 km/s) • Final slip (1.1 m)

9. Heterogeneous Source model • Slip distribution is randomly distributed subsources over the fault plane (Gallovic & Brokesova, submitted to PEPI) • Considered scaling impliesthatresultingslip distributionisk-2 (Andrews, 1980)

10. Heterogeneous source model(slip velocity)

11. Station distribution (all)

12. NS velocity component

13. EW velocity component

14. NS 1 sec 5 sec 9 sec EW Z

15. Station distribution (selected)

16. “synthetic transfer function” Models’ nomenclature Basin model included Basin model excluded Heterogeneous source model G1 G2 Homogeneous source model G3 G4 Point source model G5 G6 rG34 = G3 / G4 * G2 … uses finite-source rG56 = G5 / G6 * G2 … uses point-source

17. R 34EW comp. Rock site - additional arrivals of waves reflected from the basin

18. R 34EW comp. Rock site - additional arrivals of waves reflected from the basin

19. R 5NS comp. Great improvement of synthetics when the transfer functions is applied

20. R 5EW comp. Great improvement of synthetics when the transfer functions is applied

21. EW comp. R 6 NS comp. Same fit for rG34 and rG56 at NS comp., while better fit for rG34 at NS comp.

22. EW comp. R 6 NS comp. Same fit for rG34 and rG56 at EW comp., while better fit for rG34 at NS comp.

23. Preliminary conclusion Outlook • Use of “synthetic transfer functions”taking into account finite extent of the fault (model rG34) results generally in better agreement with exact calculation (with respect to rG56) • The method seems promising for quick scenario studies • To recompute G3 and G4 models with smooth slip function • To perform the same procedure with different scenarios (varying slip and nucleation point position) • To utilize a method for quantitative comparisons • To consider, in addition, topography in the Grenoble area