What is the depth of focus in earthquakes?

In seismology, the hypocenter or focus is the point of origin of an earthquake below the Earth's surface. The depth of this focus varies widely, with some events categorized as deep-focus earthquakes when they exceed 300 km in depth, typically occurring at convergent boundaries. Other events, such as the 2026 Kumamoto earthquake or the 2023 Turkey-Syria earthquakes, occur at much shallower depths.

What we know

• The hypocenter, also called the focus, is an earthquake's point of origin below ground. [2]
• A deep-focus earthquake is defined as having a hypocenter depth exceeding 300 km. [3]
• Deep-focus earthquakes occur almost exclusively at convergent boundaries associated with subducted oceanic lithosphere. [3]
• The 2026 Kumamoto earthquake initially struck at a depth of 10 km, later revised to 16 km. [4]

Where to go next

• how it workedWhere do deep-focus earthquakes happen?
• a case in pointWhat happened during the 2026 Kumamoto earthquake?
• what caused itHow do shallow strike-slip faults cause disasters?
• the bigger pictureWhat is seismology?
• compared withHow does surface zero differ from hypocenter?
• an unexpected connectionHow do nuclear explosions relate to earthquake hypocenters?Both nuclear explosions and earthquakes use the term hypocenter to describe their primary point of origin or energy release.

Sources

• [1]hypocenter (Wikidata Q107410) · CC0 1.0
• [2]Hypocenter · CC BY-SA 4.0
• [3]Deep-focus earthquake · CC BY-SA 4.0
• [4]2026 Kumamoto earthquake · CC BY-SA 4.0
• [5]2023 Turkey–Syria earthquakes · CC BY-SA 4.0