Even though scientists contemplate earthquakes to be either smaller versions of an earthquake, which is also referred to as foreshocks, or it being an actual earthquake, it’s still till this very day, an extremely difficult question to answer.
Scientists can thus still not determine whether signs that are related to earthquakes are actual earthquakes.
Earthquakes itself, are known as the mainshock, which is followed by an aftershock. An aftershock, or a range thereof, are collections of much smaller earthquakes, which occurs after the main quake. These are often recognised as tremors, which occur after the earthquake has done the biggest damage.
Whether aftershocks last for a few minutes, hours, days, or even weeks, all depends on the magnitude of the main earthquake. In cases where the earthquake is extremely big, aftershocks can also last for a few months to years. It, however, only occurs in severe cases.
The entire structure of an earthquake, from the foreshocks to the mainshock, to the aftershocks, all occur due to energy that gets released from one single focal point, also known as the epicentre, found at the shallow depths, of the earth’s surface. At this focal point, seismic waves occur and are so powerful that they travel at an unstable speed, which causes all the shocks. Scientists are still struggling to determine foreshocks from an actual earthquake, due to these waves being inconsistent and unpredictable.
Types of Earthquakes
- Tectonic Earthquakes – Tectonic plates are loose, cracked fragments, situated at the earth’s crust. These plates move at a slow, yet at a gradual pace, which the movement thereof then causes the plates to move either towards or from each other, which causes tremors. When two of these plates slide over one another, a tremor will occur, which is known as a tectonic earthquake. These are also known as the earthquakes that have caused the most destruction.
- Explosion Earthquakes – Caused by nuclear explosions, these earthquakes are created by people, with the biggest yet being caused during the nuclear war in the 1930’s in Japan.
- Collapse Earthquakes – These earthquakes are known as much smaller earthquakes, which generally occurs close to mines that are situated underground. They are also referred to as mine bursts and caused by the pressure, which is generated inside of rocks. When these tremors occur, it usually causes the mines’ roof to collapse, which creates more tremors, and, also, affects small residential areas and towns that surround it.
- Volcanic Earthquakes – These earthquakes occur either before or after a volcanic eruption. They can either be long-period volcanic earthquakes or volcano-tectonic earthquakes.
When the magma erupts inside the earth’s crust and leaves spaces behind, these earthquakes tend to become more severe. These spaces should always remain filled, which causes rocks from the volcano to fill it, which also results in more severe tremors.