The Fracture Attenuation Effect on Reflection Seismic Waveform Tomography

Seismic waveform tomography in reflection geometry is used to reconstruct attenuation images. This paper envisages how these attenuation images can represent subsurface fracture distributions. When the size of fractures is smaller than or equal to a half the wavelength, fractures act as single scatters and produce strong attenuation ellipses in the image. When the size of fractures approaches the wavelength, different fracture orientations have significantly different attenuation effects on the reconstructed attenuation image. Horizontal fractures act as individual interfaces and show strong attenuation in the image, and such attenuation effect increases with increasing fracture size, while vertical fractures have the weakest attenuation effect in the image. Therefore, in order to properly image the attenuation associated with fractures from different orientations, a joint inversion is needed that combines both surface and borehole seismic data, not only for broadening the available frequency band but also for including reflections from different directions in the waveform tomography.