We propose an approach for detecting localized heterogeneities from surface-wave phase-velocity and attenuation using conventional multichannel seismic data. In most surface-wave analysis, only phase information of seismic data is used to obtain near-surface S-wave velocity profiles. However, we further utilize surface-wave attenuation extracted from amplitude information of seismic data. We focus on the sensitivity difference between local phase velocities and attenuation coefficients to localized heterogeneities such as lithological boundaries and localized fractures. To characterize such heterogeneities from lateral variation of attenuation coefficients and phase velocities, we perform numerical experiments for laterally heterogeneous models with a lithological boundary and a fracture zone. We observe lateral variation of attenuation coefficients near the lateral heterogeneities. As a result, the lithological boundary can be characterized by lateral variations of local phase velocities and attenuation coefficients near the boundary. On the other hand, the fracture zone can be characterized by low lateral variation in phase velocities and increase of attenuation coefficients near the fracture. Therefore, our propose method has the possibility to distinguish lithological boundaries from localized fractures. In fluid-injection experiments (e.g., CO2 geological storage), our approach has high potential in evaluating possible existence of localized fractures, which may serve as leakage path of injected fluid.
|Title of host publication
|Proceedings of the 12th SEGJ International Symposium
|Published - Nov 20 2015