What is the focus of an earthquake?

The focus of an earthquake refers to the specific point within the Earth where the earthquake originates. This is the location where the initial rupture occurs, leading to the release of energy that generates seismic waves. Understanding the focus is crucial in seismology because it provides insight into the depth and context of the seismic event, which can help determine the potential intensity of the earthquake and its effects on the surface.

The focus is typically located at varying depths below the surface, depending on the characteristics of the tectonic activity involved. This is distinct from the epicenter, which is the point on the Earth's surface directly above the focus. Recognizing this distinction is important because it affects how the seismic waves travel and how the quake is felt at different locations.