CONCLUSIONS

Physical property models of gas hydrate-bearing sediments are important basis of seismic studies of gas hydrates.Amplitude-versus-offset analysis，full waveform inversion and reflection tomography of bottom simulating reflector must be combined with the research results of physical properties to investigate the distribution of gas hydrate-bearing sediments above BSR and free gas-bearing sediments beneath it.The analysis of AVA character of BSR shows that different reflection coefficient values but similar configurations of AVA curves are given for different combinations of different concentrations of gas hydrate and free gas.Theoretical AVA curves are useful for AVO analysis of real data.Poisson's ratio of gas hydrate models changes less and almost linearly with concentration，so there are similar configurations of AVA curves of BSR.

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Fig.7　Amplitude-versus-angle of P-P reflectionContrast between water-saturated sediment（a），model A of elastic moduli with the concentration of 10%（b）and free gas-bearing sediment，from up to down，free gas concentration changes from 1%to 2%，4%，6%，8%，10%，20%，40%，60%，80%，100%