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

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.

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.

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.