Continental Mantle Earthquakes

Category: Geography — Geomorphology and Seismology

Continental mantle earthquakes are earthquakes that originate within the Earth's mantle beneath continental regions or are associated with tectonic stresses transmitted into the mantle. Most earthquakes occur in the crust, but some seismic events originate deeper within the Earth.

Key facts

  • The Earth is divided into the crust, mantle and core.

  • The mantle extends from the base of the crust to a depth of approximately 2,900 km.

  • Most continental earthquakes are shallow-focus earthquakes originating in the crust.

  • Intermediate-focus earthquakes occur at depths of approximately 70–300 km, while deep-focus earthquakes occur at approximately 300–700 km.

  • Deep earthquakes are mainly associated with subducting lithospheric plates, where cold oceanic lithosphere sinks into the mantle.

  • Earthquakes beneath stable continental interiors may result from the reactivation of ancient faults due to changes in tectonic stress.

UPSC key pointers

  • Earthquake focus is the point inside the Earth where rupture begins; the epicentre is the point directly above it on the surface.

  • Earthquakes are classified by focal depth as shallow, intermediate and deep.

  • Deep-focus earthquakes are particularly associated with subduction zones.

  • Do not assume that all earthquakes occurring beneath continents originate in the mantle.