Using internal multiples for more accurate seismic Q estimation
M. Safari (TU Delft - Applied Geophysics and Petrophysics)
D.J. Verschuur (TU Delft - Applied Geophysics and Petrophysics)
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Abstract
Seismic waves traveling through the subsurface experience several forms of attenuation, including geometric spreading, reflection, transmission, and earth attenuation (via the so-called quality factor Q). To achieve high-resolution sub-surface details, it is essential to tackle all types of attenuation resulting from the overburden. Attenuation is associated with dispersion, causing gradual changes in signal shape and strength, leading to a shift of energy towards lower frequencies and potential signal distortion over time. Precisely measuring Q in seismic data is challenging but crucial for accurate subsurface imaging. The primary objective of this study is to explore the role of internal multiples (reflections within subsurface layers) for more accurate Q estimation, although traditional methods remove multiples in advance. Therefore, we utilize the Full Wavefield Migration method, which make use of the Full Wavefield Modeling (FWMod) scheme as its forward engine. This approach encompasses not only geometric spreading, reflectivity and transmission effects but also includes multiple scattering. The FWMod process is structured in a modular manner, where wavefield operators describe propagation and reflection/transmission. Consequently, including Q is relatively straightforward by redefining the propagator. Based on a synthetic data example it is demonstrated that multiples, when integrated into the inversion process, enhance the Q estimation.