3.1　Weighted Time-average and Wood's Equation Mode...

3.1　Weighted Time-average and Wood's Equation Model

AVA curves are shown in Fig.2for the contrast between gas hydrate-bearing sediments with the concentrations of 0%～100%and free gas-bearing sediments based on weighted timeaverage and Wood's equation model.If the concentration of gas hydrate is between 0%to 50%above BSR，P-P reflection coefficient is negative and its absolute value increases with the angle of incidence.If the concentration of gas hydrate is between 80%to 100%above BSR，P-P reflection coefficient is negative and its absolute value decreases with the angle.If the concentration of gas hydrate is between 0%to 20%above BSR，P-S reflection coefficient is negative and its absolute value increases with the angle.If the concentration of gas hydrate is between 50%to 100%above BSR，P-P reflection coefficient is positive and increases with the angle.The AVA characters of low gas hydrate concentrations are different from those of high gas hydrate concentrations.

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Fig.2　Amplitude-versus-angle of P-P（a）and P-S（b）reflections of model ofweighted time-average and Wood's equation