Why do earthquakes happen along fault lines?

Earthquakes happen along fault lines because tectonic plates move and release energy when they slip past each other.

Fault lines are fractures in the Earth's crust where blocks of rock have moved relative to each other. These fractures are often found at the boundaries of tectonic plates, which are massive slabs of the Earth's lithosphere that fit together like a jigsaw puzzle. The Earth's lithosphere is divided into several major and minor tectonic plates that float on the semi-fluid asthenosphere beneath them. As these plates move, they interact in various ways, such as colliding, pulling apart, or sliding past one another.

When tectonic plates slide past each other along fault lines, they don't move smoothly. Instead, they get stuck due to friction and build up stress over time. Eventually, the stress becomes too great, and the rocks on either side of the fault suddenly slip, releasing a tremendous amount of energy in the form of seismic waves. This release of energy is what we feel as an earthquake. The point inside the Earth where the rocks first break is called the focus, and the point directly above it on the surface is the epicentre.

There are different types of fault lines, including strike-slip faults, where plates slide horizontally past each other, and dip-slip faults, where plates move vertically. The San Andreas Fault in California is a famous example of a strike-slip fault, while the Himalayan region is known for its dip-slip faults due to the collision of the Indian and Eurasian plates.

Understanding fault lines and the movement of tectonic plates helps scientists predict where earthquakes are likely to occur, although predicting the exact time and magnitude remains challenging. This knowledge is crucial for designing buildings and infrastructure that can withstand seismic activity, thereby reducing the impact of earthquakes on human lives and property.