What is the time range of an earthquake?

An earthquake or tremor occurs when the ground shakes due to an unexpected slip on a fault. At a fault along which movement has just occurred, elastic waves are emitted by the sudden release of elastic energy stored in the rocks below the surface.

The extent of time an earthquake lasts or extends depends on its size. It is common for small earthquakes to shake for only a few seconds, but strong shaking during moderate to large earthquakes, such as the 2004 Sumatra earthquake, can last for a few minutes. This quake reportedly persisted from eight to ten minutes.

How long do earthquakes last?

It is common for earthquakes to last between 10 and 30 seconds, but some can last much longer.

In California, the 1857 Fort Tejon quake reportedly lasted between one and three minutes, one of the largest ever recorded in California.

The Great San Francisco Earthquake had less than 42 seconds of shaking in 1906, while the Northridge quake lasted only 20 seconds in 1994.

What are the factors influencing earthquake duration?

There are several factors which are responsible for influencing earthquake duration. The magnitude of the earthquake plays a major role for the tremor longer. It is also important to consider the length and depth of the fault rupture. Longer ruptures will release energy over a longer period. Seismic waves travel and linger differently depending on the type of rock and soil.

Closer locations feel longer shaking as a result of the distance from the epicentre. Furthermore, seismic wave echoes and refractions in complex geological structures can extend quaking.

Finally, aftershocks or overlapping seismic events can cause the impression of lengthy ground movement. So, the above combined factors control the duration of an earthquake.