Heterogeneity and seismic scattering in exploration environments

Seismic scattering and the corresponding reduction in signal to noise ratio is a severe limitation to seismic exploration in crystalline environments. In this paper, we summarize recent elastic numerical modeling of scattering regimes and discuss the implications for seismic exploration in shallow, hardrock environments. The resulting synthetic seismograms range from relatively transparent to highly reflective depending on the ratio of seismic wavelength to heterogeneity scale length. We note that the Archean Canadian Shield is characterized by large scale lengths, typical for crystalline environments, which translates to moderately reflective seismic sections exhibiting scattering features that are coherent over large distances. In contrast, the highly fractured footwall of the Sudbury impact structure in the Canadian Shield translates to a medium with small to moderate scale lengths, resulting in seismic sections that can in places be highly reflective or relatively transparent. From the perspective of mineral exploration in Sudbury, we find that the possible detection of massive sulfide targets is dependent not only on the shape and size of the deposit but on the scattering nature of the background as well. With information about the petrophysical properties and the distribution of heterogeneity within an exploration area, acquisition parameters such as source frequencies and minimum receiver spacing can be adjusted in order to survey within the scattering regime that will produce the least amount of noise.