Earthquake Aftermath: How Long the Shakes Last and When Aftershocks Will Fade. Even though their severity decreases with time, aftershocks after a large earthquake, such one with a magnitude of 7.1, can last for days, weeks, months, or even years. Unless an aftershock is greater than 4.0, most people in Washington State are unaware of it. Following yesterday’s significant earthquake in California, hundreds of aftershocks with magnitudes ranging from 1.0 to four have occurred in the past 24 hours.
This is a broad overview of their conduct.
Instant Aftershock Most important sequence (first few days to weeks)From Weeks to Months Extended Aftershocks
- The first few hours to days following the major earthquake are typically when the strongest aftershocks happen.
- Smaller aftershocks might last for weeks, although the most powerful ones usually happen in the first 24 to 72 hours.
- As time goes by, aftershocks progressively grow less frequent and weaker.
- Over the following few months, there may still be large aftershocks, but their frequency and intensity usually decline.
- Although they are often smaller and less frequent by this time, aftershocks can still happen months or even years following a large earthquake.
- The overall frequency and magnitude of these earthquakes will decrease, but the aftershock series may continue for a year or longer.
The magnitude of the primary earthquake usually correlates with the frequency and intensity of aftershocks. Dozens to hundreds of aftershocks are normal for an earthquake of magnitude 7.1, particularly during the first few weeks. But as time passes, there are less and fewer aftershocks.
