Seismilisus

Seismilisus is a hypothetical geological phenomenon characterized by a sustained, low-amplitude seismic tremor that affects a broad geographical area. Unlike typical earthquakes, which are sudden releases of energy from a specific fault, seismilisus is theorized to be a continuous, almost background, vibrational state within the Earth's crust. The precise cause of seismilisus remains unknown, with various theories proposed by geophysicists.

One prevailing hypothesis suggests that seismilisus could be related to widespread microfracturing within rock formations, possibly exacerbated by subtle changes in fluid pressure or thermal expansion and contraction over large regions. Another theory posits a connection to deep-seated mantle processes, where slow, persistent movements of tectonic plates or variations in the asthenosphere could generate a low-frequency hum transmitted through the lithosphere. Some researchers have also explored the possibility of anthropogenic influences, such as extensive underground mining operations or large-scale hydraulic fracturing, contributing to such pervasive tremors, although evidence for this is generally considered localized.

The detection and study of seismilisus would likely rely on highly sensitive seismograph networks capable of distinguishing subtle, long-duration vibrations from the more transient signals of typical seismic events. Understanding seismilisus could offer new insights into the rheological properties of the Earth's crust and upper mantle, as well as potentially influencing the interpretation of seismic hazard assessments by adding a component of continuous, albeit low-level, geological activity. However, seismilisus is largely theoretical, and its existence has not been definitively confirmed or widely accepted within the scientific community.