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Why do shallow earthquakes occur along spreading centres?

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World map highlighting major features of the ocean basins, including trenches, ridges, basins, and plateaus labeled throughout the Pacific, Atlantic, Indian, Southern, and Arctic Oceans. Continents are shown with shaded terrain, and prominent undersea features such as the Mid-Atlantic Ridge, Mariana Trench, and Kerguelen Plateau are marked across the map. — ocean basin Major features of the ocean basins.

Shallow earthquakes occur along spreading centres because the oceanic crust in these regions is repeatedly subjected to rifting, healing, and further rifting as tectonic plates diverge. This process creates a brittle environment in the shallow crust where earthquake-prone rocks are located.1

At these divergent plate boundaries, the crust is under significant tension. As plates move apart, magma wells up from the mantle to create new crust, and the resulting tectonic activity leads to frequent faulting. Because the heat flow from the mantle is very high at these sites, the rocks at greater depths are too hot and ductile to store the elastic strain necessary to produce deep earthquakes, confining seismic activity to the cooler, brittle shallow layers. Additionally, earthquakes occur along the transform faults that offset ridge segments, where lateral movement and slip motions further contribute to shallow seismicity.2134