The point beneath Earth's surface where rock first begin to breaks under stress and causes an earthquake

That point is known as the "focus" or "hypocenter" of the earthquake. When stress builds up in the Earth's crust due to tectonic plate movements, the accumulated energy is released in the form of seismic waves, resulting in an earthquake. Interestingly, the depth of the focus can vary widely, from just a few kilometers to several hundred kilometers below the surface, influencing how intense the shaking feels on the surface. In the real world, understanding the focus allows scientists and engineers to better assess risks in certain regions. For instance, building codes in earthquake-prone areas often incorporate data about historical earthquake foci and magnitudes to improve the resilience of infrastructure. This way, cities can withstand those shaking surprises a bit better, keeping everyone safe and secure!