One of the things we often hear after the Kahramanmaraş earthquake is the term aftershock. We can also add the term foreshocks to this term. But what exactly are aftershocks and foreshocks?
What is a precursor earthquake?
Precursor earthquakes, as the name suggests, are earthquakes that precede larger earthquakes in the same location. Such an earthquake cannot be defined as a precursor earthquake until a larger earthquake occurs in the same area. But if a big earthquake comes right after, then these earthquakes that happened before that time are called precursor earthquakes.
A forequake is defined in Wikipedia as: “A forequake is a small or moderate shaking that occurs before a major earthquake, occurring in or near the area where the major earthquake occurred.”
What is an aftershock?
Aftershocks are smaller earthquakes that occur in the same general area over the days or years following a larger earthquake or “main earthquake”. As a general rule, aftershocks represent small readjustments along a portion of the fault that slipped at the time of the main earthquake. The frequency of aftershocks decreases over time. Historically, deep earthquakes (>30 km) are much less likely to be followed by aftershocks than shallow earthquakes.
An aftershock is defined on Wikipedia as: “An aftershock is an earthquake that occurs after the main earthquake. Aftershocks occur in the center where the main earthquake was felt; but its size is lower. However, it may be of higher intensity, causing the collapse of structures weakened by the main earthquake.”
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