What is an Earthquake Focus and Epicenter?
Focus is the actual point below the surface of the earth where an earthquake originates whereas epicenter is a point directly above it, and it lies. Sources of Earthquakes and Seismic Waves Illustration show Earthquate relationships including the epicenter and focus. Earthquake vibrations (seismic waves). The earthquake focus and epicenter are two different places that occur during an earthquake. Shallow-focus earthquakes occur between 0 and 40 miles deep.
Difference Between Epicenter and Hypocenter
Activities of man are sometimes used to create seismic waves for geophysical subsurface surveys using either the seismic refraction or reflection methods. The Epicenter and Focus of an Earthquake The drawing above illustrates the epicenter and focus of an earthquake.
The focus is the point or center where the energy release starts.
The epicenter is the point on the Earth's surface directly above the focus of the earthquake. When the energy release occurs, seismic waves travel away from the focus in all directions.
Earthquake Damage The photo source: Structures constructed of many materials are prone to damage from the shaking caused by seismic waves, usually close to the epicenter of an earthquake. Body waves travel through the main body of Earth whereas surface waves are naturally limited to the surface of the planet. Body waves will be detected a greater distance from the epicenter of an earthquake than surface waves.
The two types of body waves are p-waves and s-waves.
P-waves, or primary waves, are pressure waves meaning that the oscillation of the wave is parallel to the propagation of the wave. S-waves, or secondary waves, have oscillation that it perpendicular to the propagation.
The waves get their names from the fact that p-waves come before s-waves. Shadow Zones and the Maximum Range of Detectability for an Earthquake P-waves can travel through both solids and liquids whereas s-waves will only travel through solids.
As a result, on the opposite side of the planet from the epicenter of an earthquake is a shadow zone where no s-waves from that earthquake will be detected because they would have to pass through the liquid outer core.
Although p-waves can travel through the outer core, they will be refracted in such a way that they will also not be detected on the opposite side of Earth. This region where no seismic waves from an earthquake, and thus its epicenter, can be detected is called the shadow zone.
The hypocenter is the actual point at which an earthquake occurs and the point from which body waves of an earthquake ultimately originate. What Happens at the Hypocenter Earthquakes that occur on faults as opposed to those that occur because of asteroid impacts and other nontectonic phenomena occur because of the breaking of asperities along the fault surface.
Asperities are protrusions on a fault surface that will cause two fault surfaces that are sliding against each other to get caught. After this happens, pressure will build up on the asperities until they break, allowing fault surfaces to continue sliding.
It is at this point that the earthquake occurs.
Difference Between Epicenter and Hypocenter | Difference Between | Epicenter vs Hypocenter
The vibrating waves travel away from the focus of the earthquake in all directions. The waves can be so powerful they will reach all parts of the Earth and cause it to vibrate like a turning fork.
Epicenter of an earthquake Directly above the focus on the Earth's surface is the earthquake epicenter.
Earthquake waves start at he focus and travel outward in all directions. Earthquake waves do not originate at the epicenter.
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News stories about earthquakes Most news stories on earthquakes will list the epicenter of an earthquake and then tell how deep the earthquake was from the epicenter. Great earthquakes that occur in subduction zones may give an earthquake focus but they actually break along hundreds of kilometers. The Chilean earthquake broke along kilometers of the fault line.Lecture 6: Epicenter and Focus