Välisyvyysjäristykset

Välisyvyysjäristykset, also known as deep-focus earthquakes, are seismic events that originate at depths greater than 300 kilometers beneath the Earth's surface. They are distinct from shallow and intermediate-focus earthquakes, which occur at shallower depths. Välisyvyysjäristykset are primarily associated with subduction zones, where one tectonic plate is forced beneath another into the Earth's mantle. The extreme pressure and temperature at these depths create unique conditions for rock deformation and rupture.

The exact mechanisms responsible for välisyvyysjäristykset are still a subject of ongoing research. One leading theory suggests that the subducting slab, as it descends into the mantle, undergoes dehydration. The released water can lower the melting point of the surrounding mantle rock, leading to localized melting and brittle failure, which generates seismic waves. Another hypothesis involves phase transformations of minerals within the subducting plate under high pressure and temperature, causing the rock to suddenly change its crystal structure and release energy.

Despite their great depth, välisyvyysjäristykset can still be felt at the surface, although their intensity is usually diminished compared to shallower earthquakes of similar magnitude. They are important for understanding the dynamics of subduction zones and the behavior of rock under extreme conditions within the Earth's mantle. Studying these deep earthquakes provides valuable insights into plate tectonics and the Earth's internal processes.