How Solar and Lunar Tidal Forces Trigger Slow Earthquakes: A New Model Unveils Seismic Activity Mechanisms

The Role of Tidal Forces in Earthquake Initiation

According to НВ — Техно: Researchers have developed a model demonstrating how the gravitational pull from the Sun and Moon can induce slow-moving earthquakes by subtly stressing tectonic faults. These minor tidal stresses can provoke fault slip when their timing aligns with the rock’s natural response rhythm. This breakthrough offers an explanation for the origin of slow earthquakes and their correlation with tidal cycles-a pattern confirmed by seismic data from southwest Japan and the Cascadia region. Understanding this connection provides valuable insight into seismic behavior and may enhance predictions of major earthquakes in Pacific subduction zones.

Mechanics and Observational Evidence

Tidal forces from the Sun and Moon cause slight deformations in Earth’s crust, altering the load on tectonic faults. Unlike typical earthquakes, slow earthquakes unfold over extended periods and usually go unnoticed at the surface. To simulate this process, scientists employed a spring-block system that accounts for frictional changes along fault surfaces dependent on slip velocity and contact characteristics. The tidal stress involved amounts to just a few kilopascals-equivalent to a gentle finger press.

A resonance effect emerges when the frequency of tidal loading matches the fault’s intrinsic reaction time, triggering earthquakes at various points within the tidal cycle depending on fault properties. Seismic observations in southwest Japan and Cascadia reveal increased activity at intervals near 12 or 24 hours, mirroring tidal patterns. The model focuses on small fault segments, making it particularly suited for studying localized, low-frequency seismic events.

Slow earthquakes predominantly occur in Pacific subduction zones. This research aids in correlating earthquake timing with tidal phases, allowing scientists to better characterize fault friction and rock movement. The primary tidal factors influencing seismicity include:

• magnitude of the applied stress
• duration of the stress application
• resonance between tidal rhythm and fault reaction time

Earthquakes tend to occur during peak tidal loading or moments of rapid stress change. Regions exhibiting tidal-linked seismicity include southwest Japan and the Cascadia area along the northwest Pacific coast.

This study significantly advances our comprehension of seismic processes by highlighting tidal forces as a key driver of earthquake initiation, especially in highly active subduction zones. Recognizing the influence of tides on seismic activity could improve earthquake forecasting, potentially reducing hazards to communities and infrastructure in vulnerable areas. Furthermore, the presented models lay groundwork for future investigations into how other natural factors might affect seismicity.