How Long Does an Earthquake Last?

What many people think of as an earthquake's duration is the length of time that they feel the shaking. That's reasonable, and sometimes that's the most important duration - like when we want to know how long a building has to be able to sustain strong shaking. But from a scientific perspective, when we discuss an earthquake's duration, we mean how long the rocks along the section of the fault that "fails" or "ruptures" during the earthquake are sliding past one another. Strong shaking usually lasts longer than the actual sliding of the rocks, and weaker but still detectable earthquake-induced vibrations of the Earth can take weeks to return to the normal background levels after the largest earthquakes.

The smallest earthquakes are completed in less than a fraction of a second; the largest have lasted close to eight minutes.

Mw Diameter Duration
0 10 m 0.002 s
1 35 m 0.01 s
2 100 m 0.02 s
3 350 m 0.1 s
4 1 km 0.2 s
5 3.5 km 1 s
6 10 km 5 s
7 35 km 20 s
8 100 km 60 s
9 >500 km 360-600 s

 

For more information, please see the list of Seismology Texts or the list of popular-science books on earthquake science.