Tomographically enhanced full wavefield inversion

Efficient full waveform inversion using the excitation representation of the source wavefield

“…Recently, the merger of migration velocity analysis with FWI (Symes 2008;Almomin & Biondi 2012;Allemand & Lambaré 2015;Wu & Alkhalifah 2015b;Alkhalifah & Wu 2016) has gained popularity in the context of improving the prospect of converging to a global minimum. Moreover, the isolation of desired wavenumbers in the gradient using conditioning and filtering (Albertin et al 2013;Tang et al 2013;Alkhalifah 2015;Kazei et al 2016) helps such convergence prospect. Despite the potential of all these methods to alleviate the non-linearity issue, they usually pay the price with a significant increase in computational cost.…”

Multiscale phase inversion of seismic data

“…In fact, we show that MPI reduces to that of wave equation reflection traveltime inversion under the small phase assumption. This assumes that we are exclusively using the tomographic component of the RTM operator (Mora, 1989;Tang et al, 2013) to backproject the phases of the reflection residuals. In this case the gradient takes the form of a rabbit ear for a single source-receiver pair (Schuster, 2017).…”

The optimized gradient method for full waveform inversion and its spectral implementation

“…Liu et al (2011) extended this idea to remove the low-frequency noise often appearing in reverse-time migration when sharp velocity contrasts are present in the migration velocity. Tang et al (2013) used the idea of upgoing and downgoing wavefield for extracting the tomographic components of the gradient. After decomposing the wavefield λ and μ, we can insert them into the FWI gradient…”

“…Thus, the gradient of standard FWI usually contains both the long wavelength (tomographic) components and the short wavelength (reflection) components (Mora 1989). Tang et al (2013) suggested to decompose the wavefields into local propagation angles to enhance the tomographic parts of the gradient. Liu et al (2011) suggested a similar approach to remove the RTM artefacts based on the work by Hu & McMechan (1987).…”