During the early hours of August 14, a 7.2 magnitude earthquake rocked Haiti, causing hospitals, schools and homes to collapse, destroying hundreds of lives, and leaving everything around devastated. More than 2,200 people died,12,200 people were injured, and over 130,000 homes were destroyed by the recent earthquake. Do you ever wonder if we could prevent earthquakes from happening or how do they occur in the first place? Some of you who have experienced the devastating phenomenon would definitely have been scared out of your wits. But that might not have restricted the inquisitive human mind from wandering off. Let’s dig in deeper and try to understand why earthquakes occur and how much of this disaster is preventable.
An earthquake occurs when two blocks of the Earth suddenly slip past one another. The surface where they slip is called the fault or the fault plane. The location below the Earth’s surface where an earthquake begins is called the hypocentre, and the location directly above it on the surface of the Earth is called the epicentre.
The Earth has four major layers- the inner core, outer core, mantle and crust. The crust and the top of the mantle make up a thin layer on the surface of our planet. But this layer or skin as it might be called is not all in one piece – it is made up of many pieces like a puzzle covering the surface of the Earth. These puzzle pieces, called tectonic plates, keep slowly moving around, sliding past one another and bumping into each other. The edges of these plates are called plate boundaries. They are made up of many faults, and most of the earthquakes around the world occur on these faults. Since the edges of the plates are rough, they get stuck while the rest keeps moving. Whenever these plates move far away from each other and are unable to stick to any of the faults, an earthquake is caused.
Smaller earthquakes that occur in the same place before the larger earthquakes follow are called foreshocks. The largest, main earthquake is called the mainshock. Mainshocks almost always have aftershocks that follow. Aftershocks are smaller earthquakes that occur afterwards in the same place as the mainshock. Aftershocks might continue for weeks, months, and even years after the mainshock depending on the size and intensity of the earthquake.
Earthquakes can be man-made or natural disasters. Naturally occurring earthquakes do not happen randomly. Rather, they are the result of different changes occurring in the Earth’s crust for centuries. The major causes of earthquakes fall into five basic categories:
One of the major causes of earthquakes is volcanic eruptions. When boiling lava tries to break through the surface of the Earth, with the increased pressure of gases, certain movements occur in the Earth’s crust. This sends shockwaves through the Earth, causing damage. However, these earthquakes are mild and their range is also quite limited. There are always exceptions to this as well.
The movement of the tectonic plates is categorized into three types: constructive, destructive, and conservative. Constructive is when two plates move away from each other, which leads to mild earthquakes. When two plates move towards each other and collide, this is known as destructive plate boundaries. Conservative movements refer to plates passing by near the Earth’s crust. Earthquakes occurring from this type have varying intensities.
The interference of humankind with nature can also become a cause of an earthquake. The disturbance of crustal balance due to the heavy clubbing of water in dams can lead to earthquakes. Nuclear bombing can send specific types of shockwaves throughout the surface of the Earth, which can disturb the natural alignment of tectonic plates. Finally, mining can also cause disturbance due to the extensive removal of rocks.
Some minor causes such as landslides, avalanches, heavy rocks collapsing, etc, can also cause minor shockwaves and lead to mild earthquakes.
Earthquakes caused by man-made interventions can be mitigated to a certain extent if humans tread carefully. It can be somewhat prevented by minimizing or in some cases stopping the activity that is causing the earthquakes to happen. For example, earthquakes linked to wastewater disposal in deep wells in a few places in the US stopped occurring after injection had been halted. However, it is not really possible to prevent natural earthquakes from occurring but we can significantly lessen their impact by identifying hazards, building safer infrastructure, and providing awareness and education on earthquake safety.
Do you think earthquakes can be prevented if humans became more aware of the consequences? Tell us your views in the comments below.
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