Earthquake is a phenomenon that causes seismic waves and can be natural or caused by humans. At the surface of the Earth, it can be recognized when there is a sudden shaking, displacing or disruption of the ground. The point at which an earthquake originates is represented by both epicentre and hypocenter. Both of them create a dramatic effect at the location of the earthquake.
Epicenter vs Hypocenter
The main difference between Epicenter and Hypocenter is that Epicenter appears on or above the surface of the Earth, whereas Hypocenter appears beneath the surface of Earth. The waves emitted from Epicentre is both body and surface waves while waves emitted from Hypocenter is a body wave only.
Epicentre is the exact location of the earthquake on the surface of the earth, and it spreads different waves. In simpler words, it can be said to occur above the earth’s surface. It is the focal point that is examined and researched by seismologists to comprehend the aftereffect and transmission of earthquakes. It is often suggested that the most damages are caused at the epicentre.
The Hypocenter is the point that is below the surface of the earth. It is referred to as the actual point from where earthquake ultimately originate. It is often termed as the focus or ground zero of an earthquake. Hypocenter can be tens to thousands of km deep underneath the surface. As the altitude of the hypocenter increases, the rocks become flaky and ductile.
Comparison Table Between Epicenter and Hypocenter
| Parameters of Comparison | Epicenter | Hypocenter |
| Definition | Epicentre is the point on the surface of the earth where an explosion or earthquake appears. | The hypocenter is the point of origin or sub-level of an explosion. |
| Position | It appears on or above Earth. | It appears on the sub-level or underground of Earth. |
| Waves | It causes both body and surface waves. | It causes only body waves. |
| Dimension | It measures the 2-D (D stands for dimensional) effect on how there is a spread of the waves. | It measures the 3-D effect on how there is a spread of the waves. |
| Other Names | Also known as Focal Point or Epicentrum. | Also known by the name Focus or Ground Zero. |
What is Epicenter?
Epicentre is the place where earthquake spreads radially with the 2-dimensional surface. The location from which an earthquake comes from to the epicentre can be hundreds to kilometres long. The word Epicenter was coined by the Irish seismologist Robert Mallet. Epicentre is often referred to as the ‘centre of activity of the earthquake. The focal depth of an earthquake appearing at the crust can range from 2 to 20 km.
The location of an Epicentre can be calculated by using the data from the seismograph and other measuring station, which would help to determine the kind of wave it emits. The seismic waves can be determined from hundreds and thousands of kilometres from the origin of an earthquake. There are two divisions of waves that are emitted by the epicentre of an earthquake, i.e. body waves and surface waves. Body waves usually get detected from the epicentre.
The two-division of body waves is p-waves and s-waves. P-waves are called Primary waves, which are also pressure waves in which there is a transmogrification of the wave, which is proportionate to the transmission of the wave. S-waves are called the secondary waves, in which there is a transmogrification of the wave that is perpendicular to the transmission. The waves get their names because S-waves come after the p-waves. The distance of the epicentre is also used to calculate the seismic magnitude as developed by Richter and Gutenberg.
What is Hypocenter?
A hypocenter is a cradle or birthplace where an earthquake occurs. Also known as focus or ground zero as the nuclear explosion (earthquake) takes place just beneath the ground. The hypocenter is that position of an earthquake where the energy stored in the rock, i.e. strain energy, is released and the fault of the rupture begins to appear. The fault is the fracture of the rocks where there has been a long displacement of the rock movements like a shift in the tectonic plates, which usually happens due to the earthquake.
The hypocenter, foreshocks, aftershocks of the earthquake helps in the three-dimensional plotting of the faults. Hypocenters of earthquakes can be ten to hundred or even spread across thousands of kilometres below the surface of the earth. More the depth will be of the hypocenter earthquake, it will increase the rocks around to become more soft and ductile, i.e. easily movable.
Because of the impact of an earthquake on the same area over a period of years, the rocks and stones underground will become so tender that if there is any other earthquake at the same hypocenter, then it will not be much dangerous. According to studies, the power and vigour of an earthquake depend on the pressure build on the poignant and harshness of rock before they break. So, if the rocks break or if they are already in the worst state before there is a large amount of pressure, it can accelerate, then an earthquake will not be harmful or the destruction it may cause.
Main Differences Between Epicenter and Hypocenter
- Epicentre is the point on the surface of the earth where an explosion or earthquake appears. The hypocenter is the point of origin or sub-level of an explosion.
- The epicentre of an earthquake is usually on or above the surface of Earth. The Hypocentre of an earthquake is always on the sub-level or underground in the Earth.
- Epicentre causes both body and surface waves. Hypocentre causes only body waves. Body waves contain both p & s waves.
- Epicentre measures the 2-D (D stands for dimensional) effect on how there is a spread of the waves. Hypocenter measures the 3-D effect on how there is a spread of the waves. Hypocentre can be 10 to 100 km in depth.
- Epicentre is also known as Focal Point or Epicentrum. The hypocenter is known by the name Focus or Ground Zero.
Conclusion
Both Epicenter and Hypocenter gives us information about the origin of an earthquake in an easier way. Both the terms are connected because earthquake becomes quite dangerous and dramatic at these two points. The seismic waves which are emitted during the time of earthquake spread radially from both epicentre and hypocentre.
Although the waves might be different. But epicentre is used by seismologists and scientists for many different purposes like calculating the distance, predicting the nature of the earthquake, its intensity and damaged caused and also for the magnitude of the seismic waves. Whereas the rupture of the earth surface takes place at the hypocentre.
References
- https://www.researchgate.net/profile/George_Daglish/publication/268447910_An_Algorithm_for_Concurrent_Location_of_Earthquake_Epi-and_Hypocentres_Using_P-Arrivals_in_an_Interpolative_Tabular_Scan/links/546bb8380cf20dedafd53744.pdf
- https://academic.oup.com/gji/article-abstract/209/1/453/2931730