The Earth's surface isn't a solid, unchanging shell; it's made up of several massive tectonic plates that are constantly moving, colliding, and separating. When stress builds up between these plates to a critical level, it causes a fracture, releasing a tremendous amount of energy and resulting in an earthquake. This process of stress accumulation and release is a natural part of how our planet's interior operates.

Earthquakes primarily occur in areas where faults are close to the surface, known as epicenter zones. Most earthquakes happen at the boundaries of Earth's tectonic plates, where rocks are frequently compressed or stretched.

There are three major seismic zones in the world: the Pacific Ring of Fire, the Eurasian Seismic Zone, and the Himalayan Seismic Zone.

Causes: Crustal Movements

The Earth's structure can be compared to an egg, with three distinct layers: the core is like the "yolk," the mantle is like the "egg white," and the crust is like the "eggshell." Earthquakes typically occur in the Earth's crust. Heat energy from the mantle and crust drives heat transfer between these layers, causing the crust to move. This movement leads to the compression and stretching of rocks within the crust, creating faults. When a fault is near the surface, the stress from this compression and stretching causes the rocks to shake, resulting in an earthquake.

The point where seismic waves originate is called the hypocenter, while the vertical projection of the hypocenter on the Earth's surface is known as the epicenter. The distance between the epicenter and the hypocenter is referred to as the hypo central depth. Earthquakes are classified based on this depth:

- Shallow-source earthquakes have a hypo central depth of less than 70 kilometers.

- Medium-source earthquakes have a depth between 70 and 300 kilometers.

- Deep-source earthquakes have a depth greater than 300 kilometers.

Destructive earthquakes are generally shallow-source earthquakes.

Types

1. Tectonic earthquake: A tectonic earthquake occurs due to the displacement and rupture of rock layers deep underground. These earthquakes are the most common and destructive, making up over 90% of all earthquakes globally.

2. Volcanic earthquakes: Volcanic earthquakes are triggered by volcanic processes, such as magma movement or gas explosions. These earthquakes only occur in volcanically active regions, which account for about 7% of earthquakes worldwide.

3. Collapse earthquake: A collapse earthquake is caused by the collapse of an underground cave or the roof of a mine. These earthquakes often occur in areas with dense cave systems or in regions with extensive underground mining activities.

4. Induced earthquakes: Induced earthquakes are triggered by human activities such as reservoir water storage or water injection in oil fields.

5. Artificial earthquakes: Artificial earthquakes are caused by human activities such as underground nuclear explosions or explosives detonations. Additionally, high-pressure water injection in deep wells and the creation of large reservoirs can increase pressure in the Earth's crust, sometimes triggering these earthquakes.

Prevention

When an earthquake strikes, the most effective response is to stay calm and take shelter where you are. During the quake, find a safe spot to protect yourself. After the shaking stops, evacuate quickly to a safe location.

For effective protection during an earthquake, choose a shock-absorbing location that is indoors and can support and cover your body, such as:

- Areas with triangular spaces, which offer better protection.

- Small, supported alcoves or bays.

- Open and safe outdoor spaces if you are outside.

Avoid areas that may collapse or expose you to additional hazards.

Avoid hazards such as transformers, utility poles, street lights, billboards, cranes, and other hanging or unstable objects. These can pose additional risks during and after an earthquake.