Seismic scattering signatures of small-scale heterogeneities: examples from the Mount Messenger Formation, New Zealand

Heterogeneity that is on a length scale just below that of a seismic wavelength is at the limit of resolution but may still cause significant wave scattering. A specific instance of this situation concerns seismic wave propagation through a sedimentary succession. Evidence from a high-resolution seismic experiment on the Mount Messenger Formation in North Taranaki, New Zealand, suggests that scattering from small-scale geometrical variations within the succession may be responsible for the presence of artefacts in processed seismic sections. Reflection data for this experiment have a dominant wavelength of c. 20 m, and the Mount Messenger Formation contains significant lateral variation on this length scale in the form of channel features. We model wave propagation through simplified models of these features; the resulting synthetic seismograms show that scattering and diffraction from small-scale lateral variation in elastic properties is an important effect. Simple processing steps applied to the synthetic results lead to the scattering manifesting itself as artefact in seismic image sections; these artefacts are analogous to those seen in the field data