Crustal seismic structure and depth distribution of earthquakes in the Archean Kuusamo region, Fennoscandian Shield

► In the Archean Kuusamo region, the seismogenic layer extends from about 8 km below the surface down to a depth of 30 km. ► Apparent aseismicity of the uppermost crust is explained by the excess of strong mafic material. ► The maximum depth of earthquakes correlates best with the onset of brittle-ductile transition. ► No evidence was found on movements in the lowermost crust.