The Difference Between the Epicenter & the Focus

Earthquake

• An earthquake is a vibration in the Earth's crust caused by movement of the bedrock and resulting in a rapid release of energy. This happens because of shifting continental and oceanic plates in the earth's crust. The stress caused by this movement is so intense it rips apart bedrock, stone and tear through layers of earth. Places where an earthquake has already broken the bedrock are regions likely to endure an earthquake again; they are called fault zones.

Focus

• The focus of an earthquake is the actual place where the rock breaks, producing the earthquake. This happens underground along the fault line. Seismic waves, or waves of vibration that cause the surrounding regions to shake, emanate from the focus. Seismic waves caused by a rupture of rock an at earthquake's focus travel throughout the earth. According to Berkeley University, a South Pole earthquake would shake the North Pole in less than half an hour. Thankfully, they reduce in energy as they travel, causing less and less damage as they get farther from the focus.

Epicenter

• The epicenter of an earthquake is the point on the earth's surface directly above the focus. Seismic waves issue from the focus underground, the first place on the surface of the globe to feel the waves is the epicenter. This area is the hardest hit when an earthquake occurs because the waves are the strongest. Earthquakes with shallow focus points measure larger on the magnitude scale than earthquakes with deep focus points.

Seismology

• Seismographs are instruments that geologists place throughout the earth along fault lines. They measure vibration in the earth and can tell seismologists where the epicenter of an earthquake is. The vibration must be measured by three different seismographs in order to pinpoint the epicenter, which is why scientists place them periodically. Using the magnitude of the vibrations at each instrument, they are able to extrapolate an area of focus and epicenter.