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Why are shallow earthquakes common at oceanic spreading centres?
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oceanic crust
A cross section of Earth's outer layers, from the crust through the lower mantle.
Shallow earthquakes are common at oceanic spreading centres because the oceanic crust is under constant tension as tectonic plates diverge. This process causes the crust to repeatedly rift, heal, and rift again, generating frequent seismic activity.12
These earthquakes are confined to shallow depths because only the shallow crust consists of brittle, earthquake-prone rock. At greater depths, the high heat flow from the underlying mantle prevents the accumulation of the stress necessary to produce deep-focus earthquakes. Additionally, seismic activity at these divergent boundaries is associated with the development of faults and the movement of plates along transform faults that offset the ridge crests.123