0 km
Surface
The map shows the surface location above the reported event.
Reading guide
How big? How deep?
Two numbers. Two different parts of an earthquake’s story.
Pick a report and look for four clues: magnitude, depth, location and time. Each tells you something different.
Depth guide
How deep is an earthquake?
Depth measures how far below the surface the earthquake began. The source underground is called the focus; the point directly above it on the surface is the epicentre.
10 km
Shallow report example
A depth of 10 km is in the shallow category. It describes where the earthquake began underground.
70 km
Shallow / intermediate boundary
Around 70 km is commonly used as a boundary between shallow and intermediate-depth earthquakes.
300 km
Intermediate / deep boundary
About 300 km marks the boundary between intermediate and deep earthquakes. The intermediate category runs from about 70 to 300 km.
700 km
Very deep reports
The conventional deep category spans about 300 to 700 km. These broad categories help compare reports.
Magnitude
What the number roughly means
Magnitude describes the reported size of an earthquake at the source. A higher number means much more energy was released, but it does not automatically describe damage or how strongly people felt it in every place.
Depth
Why reported depth matters
Depth is a distance in kilometres. A report marked 20 km began closer to the surface than one marked 200 km. Neither number tells you how strongly a particular town shook.
Location
Why place names can feel broad
USGS place names may describe a nearby area, offshore zone, or nearest known place rather than an exact town. The map point and source page give more context for where the report was placed.
Time
Why event and update times differ
The USGS event time shows when the earthquake occurred. The separate record-updated time shows when USGS most recently changed that record. Your browser may display both in your local time.
Safety note
Educational, not emergency guidance
This guide is for general understanding only. It is not an emergency alert system. For alerts, instructions, and local impact information, use official local authorities.
Depth categories: USGS depth explanation.