Difference Between Focus and Epicenter

There exist several natural as well as manmade calamities and disasters that may happen suddenly in our surroundings. These natural disasters include volcanic eruptions, floods, droughts, cloud bursts, earthquakes etc. During these calamities, several natural resources and places are damaged, and to avoid that damage and to protect human life in that area, there have been made many discoveries and inventions that help to collect data on these disasters. For knowing and collecting data regarding an earthquake that takes place in a certain location, various concepts are used.

During an earthquake, various small activities take place that results in damage to the land. There is an independent branch of science that deals with the study of earthquakes. That branch is known as seismology. In seismology, two of the main things that are studied are 1. Focus and 2. Epicentre.

Focus vs Epicenter

The main difference between focus and epicentre is their location. The focus is that part of the earth where the rocks that are stressed under the surface of the earth is present. On the other hand, the part of the earth’s surface that is present right below the focus is known as the epicentre.

Focus and Epicenter

In seismology, the focus of the earthquake is that part of the earthquake that is where the waves come from. The seismic waves spread widely when they pass from the focus of the earthquake. The focus of the earthquake is located right above the epicentre of the earthquake. The focus is also addressed as the hypocentre.

In seismology, the point of the origin of the earthquake is known as the epicentre. The epicentre is right below the hypocentre of the focus. During an earthquake, the initial explosion in the ground takes place in the epicentre. Since the epicentre is the part where the explosion begins, it is also the part where the damage is caused the most.

Comparison Table Between Focus and Epicenter

Parameters Of ComparisonFocusEpicenter
LocationThe subsurface of the earth.The surface of the earth.
WavesThe associated wave is the body wave.The associated waves are body waves and surface waves.
PositionBelow the earth’s surface.On the earth’s crust.
Used forTo take measurements of the three-dimensional speed waves.To take measurements of the two-dimensional spread waves.
Earthquake The earthquake rupture is initiated here.The earthquake waves originate here.

What is Focus?

The focus of the earthquake is also known as the hypocenter. The seismic waves that are produced during an earthquake consist of radiation. This radiation of waves begins at the focus. The earth’s crust consists of several rocks that are ruptured during an earthquake. When the radiation begins, the rupturing begins too. The rocks are then ruptured further gradually. As these rocks experience stress from the beginning itself, the radiation causes rupture, and the stress adds more rupture to it.

The waves originate at the hypocentre, and they further travel to the epicentre. As epicentre is situated right above the focus, it experiences the strongest waves during an earthquake. As these waves travel ahead, they become less effective. The place surrounding the focus is always in motion even though the ground that humans stand on is still.

The focus is the point where not only seismic waves originated but also their various forms are originated in the focus. These seismic waves are focused or collectively formed near the focus, which is further expanded and travel through various parts of the earth’s crust, including the epicentre. At that time, the waves of several types travel at different speeds as well as time. The motion of these waves is different too.

Several rocks are present in the earth’s crust. The earth’s crust is made up of those rocks. When the seismic waves originate and further travel towards the entire area of the crust, several cracks are developed in the rocks. These are known as fractures. After these cracks are developed, the waves travel forward to the epicentre, which is situated right above the focus.

What is Epicenter?

An epicentre is one of the parts of the earth’s crust that lies right above the earth’s hypocentre or the earth’s focus. As the epicentre is the closest point near the hypocentre, the waves that originate from the focus hits the epicentre first, and then they travel further to the other parts of the earth’s crust.

As the epicentre is the closest to the hypocentre, it is the part of the earth’s crust that experiences more damage than many other parts. However, in some cases, when the subsurface is long enough, then the damage is divided into all the parts, and the epicentre is equally damaged. 

Now, scientists can also measure the distance of the epicentre. This distance is known as the epicentral distance. In seismology, the epicentral distance is measured in degrees, and it is measured majorly by using the formula of Laska’s empirical rule. When an earthquake occurs in a certain region, the epicentral distance is measured along with other measurements to record the data.

Robert Mallet was a seismologist that tossed the term epicentre. The Epicentral distance is useful to calculate the magnitude of the earthquake that occurs in a location. The fault rupture of the total area and the magnitude are related to each other of the earthquake.

Main Differences Between Focus and Epicenter

  1. The focus is situated in the earth’s crust. On the other hand, the epicentre is situated on the earth’s crust.
  2. The focus is also known as hypocentre. On the other hand, the epicentre does not have any other name.
  3. The focus is the origin of the seismic waves. On the other hand, the seismic waves travel and pass through epicentre after they begin from the focus.
  4. The epicentre is located above the focus. On the other hand, the focus is situated below the epicentre.
  5. The epicentre experiences comparatively more damage. On the other hand, the focus experiences comparatively less damage.

Conclusion

Both epicentre and focus help many scientists and seismologists to collect data whenever an earthquake occurs in a particular location. These various parts of the earth’s surface have independent features, and they consist of several materials.

During a calamity, various types of properties and human life are damaged. Many people lose their lives and their properties. The wildlife is also endangered during such disasters. By calculating and collecting data regarding the calamity, a convenience is created as it gives an idea regarding the damage and further steps that need to be taken.

References

  1. https://pubs.geoscienceworld.org/ssa/bssa/article-abstract/76/3/771/118862
  2. https://link.springer.com/article/10.1007/BF00876083
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