Converted Waves From Gas Hydrates: Constraints On The Shear Velocity Structure Of Shallow Sediments In Oregon Continental Margin

Gas hydrates are frozen methane gas that can be found<br>along most continental margins worldwide. Estimates<br>of elastic properties of hydrate-bearing sediments are<br>essential to evaluating the gas-content. Robust<br>est1imates of these parameters can be obtained by prestack<br>inversion. However, the conventional streamer<br>data cannot constrain the shear wave velocity well; a<br>property that is essential to identification and<br>quantification of gas. Here we report on the first<br>observation of converted waves from hydrate-bearing<br>sediments recorded on multi-component ocean bottom<br>seismometers deployed during a field survey across<br>the Oregon continental margin. We employ plane<br>wave processing including interactive P and S wave<br>velocity analysis of the data to obtain robust estimates<br>of these parameters. The results are extremely useful<br>in characterization of gas hydrates in continental margins.