Lithosphere-Atmosphere-Ionosphere Coupling (LAIC)
The Lithosphere-Atmosphere-Ionosphere-Coupling (LAIC) Theory describes how the atmosphere and ionosphere react to earthquake processes during a time period (up to two weeks) before an earthquake happens. This theory thus demonstrates that the earthquake preparatory phase involves both the Earth’s crust as well as the atmosphere and ionosphere.
The stored strain and stress at the last stage of the seismic cycle cause a transition from elastic deformation to non-elastic cracking and fracturing. This activity opens new pathways for crustal degassing consisting mostly of carbon dioxide, methane, hydrogen, helium, radon, amongst others. Radon, produced by radioactive decay of the uranium-radium chain, emits high energy (5.6 MeV) particles, thus directly affecting the state of the atmosphere.
In the case of intensive radon emissions, the atmosphere from the near ground up to the upper layers of the “Atmospheric Boundary Layer” (nearly 2 km) is modified. The ionization of the atmosphere by these particles creates a large number of ions, which cause further chemical reactions and the subsequent formation of complicated ion clusters. Due to their dipole structure, water vapor molecules attach themselves to the newly formed clusters. The hydrated ion clusters grow very fast reaching the aerosol size. This process is called the Ion Induced Nucleation (IIN).
How does this process manifest itself in atmospheric monitoring data?
- IIN causes a decrease in the amount of water vapor in the atmosphere leading to an anomalous drop in the air’s relative humidity.
- During hydration, the water molecules change their phase state from gas to a bounded-to-ions state. Phase changes release some energy in a form of latent heat. This heat is emitted by the water molecules into the atmosphere while attaching to the ions, which leads to an increase in air temperature.
- According to Dalton’s law, the atmospheric pressure is a sum of partial gas pressures, including water vapor. If the relative humidity sharply drops, the air pressure drops proportionally.
The LAIC theory studies how these processes are linked in the earthquake preparatory process. We developed the so-called integrated parameter – Atmospheric Chemical Potential (ACP), which considers all processes mentioned above and is used in our technology as a short-term earthquake precursor. Before most large earthquakes, the ACP reaches the absolute maximum up to 15 days BEFORE the actual event, followed by a sharp drop of its magnitude 0-3 days before an earthquake. The spatial size of the observed ACP anomaly also allows for earthquake magnitude estimation, and the position of the anomaly center – to estimate its epicenter coordinates.
Our research also shows that the ACP trends are highly correlated to the shear traction produced by the tectonic waves. One such example is illustrated in the figure below for the region of the Aleutian Islands since August 2021. The red color illustrates regions with positive correlation between the ACP and the shear traction. The graph illustrates the time-development of the shear traction (red) and ACP (blue line). Based on the fact that such correlation can be found in many regions worldwide, we conclude that the Omega- and the LAIC theories are consistent/compatible and allow for effective operational earthquake forecasting.
The second important consequence of the air ionization produced by radon is the change of electric properties of the boundary layer of the atmosphere.
We live in the electricized environment provided by global thunderstorm activity. This activity creates a strong potential difference (nearly 240 kV) between the upper layers of the atmosphere (higher than 60 km) (the ionosphere) and the ground surface. In fair weather areas, this potential difference creates the reverse current from the ionosphere to the ground. This global system is called Global Electric Circuit (GEC). Its equivalent circuit is presented in the figure below.
Assuming the constant return current while the boundary layer resistance RBL drops due to increased ionization and the formation of a large number of light ions, the total column resistance will drop, consequently leading to a total voltage drop and lowering of the ionospheric potential IP. While the large cluster ions after hydration start to prevail over the light ions, the conductivity of the boundary layer decreases, the RBL is growing, and the IP increases. It was established that these variations of IP lead to the formation of negative and positive large-scale irregularities of electron concentration in the ionosphere. The shape, size, and location of the seismic-ionospheric anomalies depend on the longitude of the impending earthquake epicenter and other geophysical conditions. Nevertheless, we are able to develop procedures for automatic recognition of the ionospheric precursors of earthquakes. This opens the way to use this technology in immediate to short-term earthquake forecasts.