Infrasointia

Infrasointia is a hypothetical subsurface geological province described in geophysical literature as a zone of persistent low-frequency seismic signals beneath the Arcadia Basin on the Valeron Craton. The concept was proposed to explain anomalies not accounted for by conventional crustal models.

Etymology: The name combines infra- meaning "below" with a neologism referencing sound, reflecting the province’s characteristic signals.

Evidence comes from long-baseline seismic arrays and magnetotelluric surveys, which indicate a large, subcrustal anomaly with low seismic velocities and high conductivity. No direct drill data has confirmed the feature.

Geography and geology: Envisioned to lie mainly beneath the Arcadia Basin, it is posited to extend several tens of kilometers below the crust and consist of partially molten mantle material intruded by basaltic sills, affecting regional tectonics.

Geophysical signatures: Models predict low P- and S-wave velocities, elevated electrical conductivity, and distinctive heat-flow patterns associated with the zone.

Significance: If validated, Infrasointia would influence interpretations of crustal structure and geothermal potential and prompt new drilling programs. At present it remains a theoretical construct with competing explanations.