Difference Between Earthquake and Aftershock

Earthquake vs Aftershock

Earthquakes and aftershocks are both tremors that happen due to the release of energy from the crust of the Earth. There is a whole branch of science devoted to earthquakes. They are of different magnitudes and very different types. The main thing that differentiates an earthquake from an aftershock is the magnitude of the quake arising from the same epicenter.

Earthquake
Earthquakes are commonly called “quakes” or “tremors” and happen because of the seismic waves arising from the crust of the Earth due to a sudden release of energy. Earthquakes manifest themselves on land as well as offshore. When the quake manifests itself on land, the surface shakes and the ground is displaced. Sometimes, due to the shaking, buildings, trees, and other man-made and natural things are damaged as per the magnitude of the shaking. It also causes volcanic activity and landslides sometimes. When quakes manifest themselves offshore, sometimes the seabed is displaced and can cause a tsunami.

Earthquakes can be caused by natural or human reasons. Any seismic activity is considered an earthquake when it generates seismic waves. Earthquakes are caused by “geological fault ruptures” thus many activities may lead to an earthquake like landslides, volcanic activity, and human reasons like mine blasts and nuclear tests. It is a vicious circle. Earthquakes may result in natural disasters like volcanic activity and landslides, and these activities may lead to earthquakes.

The point of rupture of an earthquake is called a hypocenter or focus, and the point just above the hypocenter at the ground level is called an epicenter. Earthquakes are measured by seismometers. The frequency of earthquakes, their size, and magnitude is referred to as seismic activity. The Richter scale is used to measure earthquakes less than a magnitude 5, and globally a magnitude larger than 5 are measured by a Moment Magnitude scale. Main shocks occur in the complete fault rupture area in the fault plane or along faults which are within the area of the main shock.

Aftershocks
The first seismic wave generated from the epicenter which is of the highest magnitude is considered the main shock, and the shocks that occur after the main shock that are of lower magnitude are called aftershocks. The main shock and the aftershocks are always in the same region, but their magnitudes are different. If an aftershock is of a higher magnitude than the original shock, then the aftershock is referred to as the main shock, and the main shock is redefined as a foreshock.

Aftershocks occur as the crust of the Earth adjusts itself to the displaced plane. Aftershocks occur away from the fault plane in a distance which is equal to the length of the rupture.

Summary:

1.The main shock of an earthquake is of a higher magnitude than the aftershock.
2.An earthquake and its main shock usually occurs in the complete fault rupture area in the fault plane or along faults which are within the area of the main shock whereas an aftershock occurs away from the fault plane in a distance which is equal to the length of the rupture.
3.Earthquakes occur due to a displacement of the ground; aftershocks occur as the crust of the Earth adjusts itself to the displaced plane.

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