Earthquake GK: focus, epicentre, magnitude and intensity
The focus is where an earthquake starts underground; the epicentre lies above it at the surface. Magnitude describes event size, while intensity describes local shaking.
The focus is where an earthquake starts underground; the epicentre lies above it at the surface. Magnitude describes event size, while intensity describes local shaking.
Locate the earthquake
USGS identifies the underground starting location as the hypocentre, also called the focus. The epicentre is the point on the surface directly above it. Think of a dot inside a transparent box and a second dot vertically above it on the top face: that is an original visual analogy for the relationship.
Size and shaking
USGS distinguishes magnitude, a measure of an earthquake’s size, from intensity, the shaking experienced at a particular place. One earthquake can therefore produce different intensities in different locations. A report of stronger shaking in one town does not automatically imply a different earthquake magnitude there.
Read a news report carefully
When you see an earthquake headline, look for the event time, the location, depth, the named reporting agency and whether a value is preliminary. This page explains terminology; it does not report a new earthquake or supply live safety instructions.
A short revision exercise
Match four descriptions to four terms: underground origin, surface point above the origin, event size, and local shaking. The answers are focus, epicentre, magnitude and intensity. Keep the position terms separate from the measurement terms. For current event information, use an official earthquake monitoring service.
Publication disclosure
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Frequently asked questions
Can one earthquake have different shaking intensities?
Yes. Intensity describes shaking at a location, so it can vary between places.