Deep quake
scientists at the uk-based University College of London (ucl) have recreated earthquakes in the laboratory. This is the first time scientists have been able to generate and observe deep and intermediate focus earthquakes in the laboratory, recreating the exact pressure and temperature conditions of the deep Earth.
Intermediate and deep earthquakes occur at a depth of 70 and 650 kilometres (km) under the Earth. They are triggered by various chemical reactions that occur in down-going material below the subduction zones (most of the Pacific coastline, for example). They can be extremely large; the largest deep earthquake ever recorded was at a magnitude of 8.3 and occurred 600 km below Bolivia in 1994. The odd thing about deep earthquakes is that they shouldn't happen. Earthquakes require brittle failure and frictional slipping, which is not found in very deep layers of the Earth.
David Dobson and his colleagues from ucl brought together a unique collection of skills and techniques to study the dehydration reactions that can occur at a depth of 300 km below the subduction zones. Their results show that these dehydration reactions can cause a phenomenon known as
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