Heterogeneity parameters inversion from the energy of seismic scattering waves: verification from physical modelling experiments

SUMMARY Seismic scattering waves in random media are usually regarded as noise in conventional seismic imaging, inversion and interpretation. However, the spatial and temporal variation of the scattering energy depends on the stochastic properties of the random media. The extraction of heterogeneity information such as the correlation scale and fluctuation strength from seismic scattering waves remains a challenge. These parameters are inverted from real scattering data by fitting the synthetic envelopes to the observed seismic envelopes. The synthetic envelopes are usually computed using the Monte-Carlo radiative transfer (MCRT) method. However, physical verification of the stochastic parameter inversion based on MCRT theory has not been realized although it is believed to be correct. To this end, we conducted a physical modelling experiment using an ultrasonic acquisition system and recorded the transmitted wavefields through an artificial heterogeneous medium. In this paper, the elastic MCRT method was used to simulate the energy transport, and the correlation length and fluctuation strength of the artificial heterogeneous medium were inverted with a revised objective function, which can better balance the energy level of direct waves and scattering waves in the inversion process. The inversion results of the correlation scale and fluctuation strength match well with true values, suggesting that this method is accurate and reliable. A combination of our physical experiments and the MCRT theory gives strong proof that this inversion method is correct. Therefore, it can be used with confidence to estimate the properties of the heterogeneities from the ‘undesired’ scattering waves, both in the oil/gas exploration and earth structure investigation.