Amplitude and phase changes for reflected and transmitted waves from a curved interface in anisotropic media

Abstract

Summary It is well known that seismic data that have been recorded in complex geological environments must be compensated for geometrical spreading before AVO/AVA analysis, in order to avoid erroneous imaging interpretation. By investigating analytically both the effect of the geometrical spreading and the effect of the reflector curvature on amplitude and phase changes for reflected and transmitted waves between anisotropic media, using ray theory, we show that these data should be compensated for interface effects as well. In order to gain insight more specifically in the focusing effect of the interface, the special case of homogeneous isotropic media separated by a curved interface of syncline type is discussed and compared to the case of a plane interface. 3D numerical simulations of wave reflection from curved interfaces using a Spectral-Element Method validate our analytical derivations. In particular, numerical seismograms obtained at a vertical receiver array highlight that the effect of interface curvature on the reflected events is much more pronounced in a restricted area associated with the existence of caustics, which is consistent with our analytical predictions. Moreover, comparisons between the numerical and the analytical results confirm the fact that using plane-wave reflection coefficients without correction for the interface effect may lead to wrong interpretation of AVA/AVO analysis.

A New Predictive Hypothesis for Phase Difference Reflection in GHz

“…One study on the effect of reflector curvature on signal amplitude and phase changes for reflected and transmitted waves between general anisotropic media revealed via comparison between numerical and analytical outcomes that using the plane-wave reflection coefficient without correction for the interface effect could lead to inaccurate interpretations of AVA/AVO analyses (note: AVO refers to amplitude-versus-offset and AVA represents amplitude-versus-angle) [4].…”

Common Transmission Point (CTP) Gathers: A New Domain for Amplitude Variation with Offset

“…The results of this study describe that the data should be corrected for the effects of interface by using ray theory to investigate the impact of reflector curvature and geometrical spreading on phase and amplitude changes for transmitted and reflected waves within anisotropic materials. An unusual scenario of homogeneous isotropic materials which are separated by a sloping interface was investigated in order to gain a better idea of the focusing effect of the contact [19]. Popoola et al (2019) introduced the concept of transmission amplitude variation with offset (TAVO) by putting the Aki-Richards T PP approximation [20] in a Shuey-like form and expanding their T PS approximation in an odd-powered sine series [21].…”