The Tertiary auriferous gravels of California’s Motherlode belt — Eocene-age channel deposits buried under volcanic mudflows and laterite — are an appealing theoretical target for L-band fully polarimetric SAR, though the degree to which each scattering mechanism actually responds to subsurface structure in this environment remains an open question. The following discussion outlines plausible physical mechanisms, but it should be noted that peer-reviewed validation of Yamaguchi decomposition for buried paleochannel detection in vegetated, geologically complex terrain is limited.
This is arguably the most interesting component for subsurface investigation. At 24 cm wavelength (e.g., NASA’s UAVSAR), the signal can theoretically penetrate several meters into dry, low-conductivity material. A buried alluvial gravel deposit — coarse, poorly sorted Eocene gravels with mixed clast sizes, variable moisture, void spaces, a