What causes earthquakes in plate tectonics?

Earthquakes occur through various mechanisms related to tectonic plate movements, including interplate boundaries, plate interiors, and deep subduction zones. In subduction zones, plates sink into the mantle where intermediate and deep-focus earthquakes can happen along Wadati-Benioff zones. While shallow and interplate mechanisms are well understood, the exact physical behavior causing deep-focus earthquakes under extreme pressure remains fully unverified.

What we know

• Interplate earthquakes occur on the boundaries of tectonic plates, whereas intraplate earthquakes happen in the interior of a plate. [3]
• Earthquakes occurring within a subducting plate are referred to as intraslab earthquakes. [3]
• Deep-focus earthquakes occur in subduction zones at depths ranging from 300 km to 700 km. [5]
• One possible mechanism for deep-focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure. [5] · medium confidence

Still open

• The exact cause of deep-focus earthquakes is still not entirely understood, since subducted lithosphere at high pressure and temperature regimes should not exhibit brittle behavior.

Where to go next

• the bigger pictureWhat is an intraplate earthquake?
• how it workedHow do depth of focus categories differ?
• a case in pointWhat is the Juan de Fuca Plate?
• what caused itWhat happens at the Cascadia subduction zone?
• compared withHow does the 2026 Tibet earthquake compare to subduction events?
• an unexpected connectionHow do minerals transform deep inside the Earth to cause quakes?Deep earthquakes are linked to microscopic crystal phase changes where minerals like olivine alter their structure under extreme mantle pressure.

Sources

• [1]Juan de Fuca Plate (Wikidata Q860385) · CC0 1.0
• [2]Juan de Fuca plate · CC BY-SA 4.0
• [3]Intraplate earthquake · CC BY-SA 4.0
• [4]2026 Tibet earthquake · CC BY-SA 4.0
• [5]Depth of focus (tectonics) · CC BY-SA 4.0