1. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Seismic wave Propagation and Imaging in Complex media: a European network XUAN NHI NGUYEN Early Stage Researcher Host Institution: Universität Hamburg Place of Origin: Hanoi, Vietnam Appointment Time: Jan 2005 Project: Modeling of Scholte wave propagations at seafloor. Task Groups: Small scale group Cooperation: S.Heimann (U.Hamburg), University of Trieste, ETHZ, Schlumberger XUAN NHI NGUYEN Early Stage Researcher Host Institution: Universität Hamburg Place of Origin: Hanoi, Vietnam Appointment Time: Jan 2005 Project: Modeling of Scholte wave propagations at seafloor. Task Groups: Small scale group Cooperation: S.Heimann (U.Hamburg), University of Trieste, ETHZ, Schlumberger

2. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Project Scope Description of Seafloor * Consists of unconsolidated sediments in the uppermost layers. The sediment layer thickness is about few m to hundred of metres. * The acoustic/elastic properties are thus generally close to those of water. *S-wave velocity is small (few tens-few hundreds metres per second). Scholte wave * The interface wave that travels along the fluid-solid interface. * Scholte wave, in some cases, considered as Rayleigh wave.

3. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Project Scope Goal *In-depth understanding of fundamental physical processes governing Scholte wave propagation and sensor-seafloor coupling. *To evaluate the implications for seafloor recording and processing. *Development and improvement of techniques to attenuate ringing phases, body wave reverberation, sensor cross coupling and noise. *To constrain seafloor properties from seismic waveforms.

4. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Project Scope 1-Study the interface waves (Rayleigh wave, Scholte wave..). 2-Data preprocessing and plotting of seismic profiles. 3-Waveform forward modelling. 4-Inversion of data, interpretation and publication. 5-Study effects of anisotropy, ringing phase, effect of attenuation, effect of topography and to implement numerical models. 6-Interpretation of the results and publish papers. 7-Study the effect of station coupling and rocking. Simulate with the use of finite element methods.

5. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Main Results OBS profile with strong Scholte waves excited by seafloor implosion source.

6. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Main Results Waveform modelling with the use of Qseis, a reflectivity code

7. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Main Results Waveform modelling with the use of Qseis, a reflectivity code

8. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Main Results Inversion with CPS (Computer Programs in Seismology)

9. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some Modeling with Chebyshev-Fourier code (Chant) Z X Model with thick sediment layer Uniformly 100m- spacing-receivers Implosive source

10. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some Modeling with Chebyshev-Fourier code (Chant) Model with the “hill“ topography Model with the “dip“ topography Model with very thin sediment layer Model with the “slope“ topography

11. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the thick sediment layer t=0.2s t=0.5s t=0.53s t=1s

12. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the thick sediment layer t=1s- Pressure

13. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the thin sediment layer t=0.34s t=0.58s t=0.9s t=1s

14. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results t=1s Model with the thin sediment layer

15. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the “hill“ topography t=0.2s t=0.5s t=1s t=2.32s

16. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the “hill“ topography t= 2.32 s- Pressure

17. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the “dip“ topography t=0.2s t=0.5s t=1s t=0.8s

18. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the “dip“ topography t=1s- Pressure

19. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the “slope“ topography t=0.2s t=0.5s t=1s t=0.8s

20. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Some preliminary results Model with the “slope“ topography t=1s -Pressure

21. www.spice-rtn.org SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Outlook **Potentially, the studies may lead to the formulation of effective seafloor properties that may be useful for other studies ***Future research will concentrate on the effects of anelasticity, anisotropy and seafloor topography on Scholte wave propagation and amplitudes. * Paper in preparation: Shear wave velocity and waveform models of the Ninetyeast Ridge region obtained from Scholte waves.