Assessing the Neotectonic Processes on Changes in the Sea Level of the Caspian Sea

Long-term fluctuations in the Caspian Sea level pose a major challenge for the countries of the Caspian region, as they are of significant magnitude and can have catastrophic economic consequences. The prevailing climatic hypothesis (runoff/evaporation balance) explaining the causes of Caspian Sea level fluctuations is supplemented by a geological hypothesis that accounts for the influence of geological processes. Fluctuations in the Caspian Sea level are influenced by a combination of climatic factors and geological processes, including compression and extension of the Earth's crust, as well as vertical and horizontal tectonic movements. A geofluid dynamic hypothesis is considered, which posits that in fault zones of the Earth’s crust, seismic phenomena trigger alternating periods of compression and extension. These events influence the subsurface flow into the sea, periodically increasing and decreasing it through the process of "expulsion" or "absorption," whereby water and fluids saturating the bottom sediments are either expelled or absorbed. This study explores the correlation between modern fluid dynamics and seismic events within the context of the geofluid-dynamic model we have developed. The model is based on shallow geophysical data and suggests the need to amend the Caspian Sea water balance equation by introducing a coefficient for the inflow and outflow of subsurface fluids. Analysis of this model revealed a strong correlation between vertical seismo-acoustic anomalies—the ”pipes” or ”chimneys” through which fluids migrate—and megathrust earthquakes occurring worldwide. This model has significantly refined the previously hypothesized link between fluctuations in the Caspian Sea level and regional earthquakes. Global earthquakes with magnitudes of M>8.3 are considered the primary external indicator of neo-tectonic activity and a parameter for predicting sea-level changes.