Earthquake vs. Aftershocks

Difference Between Earthquake and Aftershocks

The earthquake and aftershocks are the classification of tremors that come in groups in case of an earthquake. The earthquake is a natural disaster that can cause devastation in large areas. Sometimes, small tremors are experienced days before the earthquake strikes. These tremors, mild or strong are called foreshocks. In a similar way, it is common for a place that has experienced massive earthquake to feel smaller tremors in the days to come after the earthquake. These are aftershocks. People are often confused about the difference between the earthquake and the shaking or aftershocks which disturb a person mentally after he has already been affected by earthquake. This article aims to bring out the differences between the two.


The earthquake is sudden and massive tremor that results due to the release of seismic energy from below the crust of the earth. These earthquakes occur without any warning but some places are more geographically more prone to earthquakes than others and this is why they experience earthquakes more frequently. The earthquake occurs mainly due to the rupture of geological faults, but also occurs as a result of volcanic activity and landslides. Earthquake is also caused due to human activities such as mining and nuclear testing. The point from where the earthquake originates is known as hypocenter and the point on the earth above this hypocenter is known as epicenter.

The extent of an earthquake is measured by the Richter scale and is rated between values of 1-9 on the scale. The larger value on the scale indicates the high intensity of earthquake. In general, as a shallow earthquake, more devastation it can cause on the earth’s surface.


As described earlier, the earthquake normally comes in groups that are classified as foreshocks, the main earthquake and aftershocks.  Aftershocks are also the earthquake, but they have very low intensity no or very less damage, but there have been cases where the aftershocks were very intense and were called as the mainshock later. Thus it is clear that these shocks are related to each other. As a general rule, an aftershock should occur after the earthquake, and should have a rupture length of the original fault rupture.

Based on past experiences, people expect the aftershocks after the main earthquake and this is the big difference between the earthquake and aftershocks. There is no way to expect an earthquake, but people are psychologically ready for aftershocks. In general, the frequency and number of aftershocks decreases with time after the earthquake. The aftershocks are more frequent during the first few hours of the earthquake and almost half of the aftershocks are estimated during the hours of the earthquake. It was noted that the intensity of the aftershocks also depends on the intensity of the earthquake. So if the earthquake was measured high on scale then aftershocks will also be intense.

In general, although the aftershocks are similar in nature to the earthquake, they, despite not as strong as the earthquake can still damage property and cause loss of human and animal life.


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