Mid-Term Review Meeting, February 13-14, Tutzing 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: Seismic wave propagation in unconsolidated media. Task Groups: Small scale group Cooperation: 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: Seismic wave propagation in unconsolidated media. Task Groups: Small scale group Cooperation: University of Trieste, ETHZ, Schlumberger

Mid-Term Review Meeting, February 13-14, Tutzing Project Scope Description of Seafloor * Consists of unconsolidated sediments in the uppermost layers * The acoustic/elastic properties are thus generally similar to those of water. *Velocity increase with depth and Poison ratio reduce with depth. *The mushy layer thickness is about few m to few hundred m. *The mushy layer assumed to be strongly attenuated at high frequencies and possible porosity and anisotropy. Goal *In-depth understanding of fundamental physical processes governing 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.

Mid-Term Review Meeting, February 13-14, Tutzing 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 ringing phase, effect of attenuation, porosity on the excitation of ringing phases 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.

Mid-Term Review Meeting, February 13-14, Tutzing Main Results OBS profile with strong Scholte waves excited by seafloor implosion source.

Mid-Term Review Meeting, February 13-14, Tutzing Main Results Waveform modelling with the use of Qseis, a reflectivity code

Mid-Term Review Meeting, February 13-14, Tutzing Main Results Waveform modelling with the use of Qseis, a reflectivity code

Mid-Term Review Meeting, February 13-14, Tutzing Main Results Inversion with CPS (Computer Programs in Seismology)

Mid-Term Review Meeting, February 13-14, Tutzing 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. Some parts of the items are going to be implemented at the Uni of Trieste, with the use of the code of the OGS(Trieste). *Paper in preparation: Shear wave velocity and waveform models of the Ninetyeast Ridge region obtained from Scholte waves Intended Journal: Journal of applied Geophysics