Seismology - Background, Significance, Measurement, Features and Other Details for UPSC

Seismology is the study of earthquakes and seismic waves that travel through and around the Earth. Specialists who research earthquakes and seismic waves are called seismologists. Seismology is the scientific study of earthquakes and the behavior of Earth's interior. Seismologists use instruments called seismometers to detect and record ground motion. Earthquakes are caused by the sudden release of energy in the Earth's crust, leading to seismic waves. Seismic waves provide valuable information about the Earth's structure and composition. The point on the Earth's surface directly above the earthquake's origin is called the epicenter. Seismologists analyze seismic waves to understand the magnitude and depth of earthquakes. Studying seismic activity helps assess earthquake risk in different regions.

The topic of Seismology is particularly important from the exam point of view as questions can be asked about this topic in both the preliminary (GS Paper 1) exam and the mains examination (GS Paper 1) under Physical Geography Section of of UPSC.

In this article on Seismology, we shall discuss what it is, its history, significance, issues associated & other details. This will be very useful for aspirants in the UPSC Prelims Exam.

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What is Seismology?

It is a particular branch of geology or science that focuses on earthquake research. Investigating earthquakes and the theories that explain them is a scientific and interdisciplinary field. Seismos, which means earthquake, and logy, which means study, combine to form the word ‘Seismology’ which means study of earthquakes. The study of seismic waves, which are created when energy travels beneath the surface of the Earth in the form of waves, is known as seismology.

Seismology: A Background History

• People first began describing earthquakes and volcanoes in writing about 4,000 years ago. It has been 26 centuries since people first began examining earthquakes’ natural causes.
• In reaction to the Lisbon earthquake of 1755, John Bevis and John Miehell carried out the first modern seismological examination in 1757.
• It peaked during Robert Mallet’s dismal speeches (1862).
• The first teleseismic record was made in Potsdam by Ernst Yon Rebeur-Pasebwitz, while John Milne and his associates in Japan constructed the first modern seismograph prototype in 1889.
• Thanks to long-period seismographs and computers, seismology can now fully benefit from the amount of data present in seismic signals, both locally and globally (1934–1962).

Father of Modern Seismology

• John Milne is credited with creating modern seismology.
• As a result of his research, he was able to recognise the different P-wave, S-wave, and surface wave arrivals on seismograms.

Measurement of Seismology

There are two main instruments used in seismology which are discussed below

Seismographs

Seismographs are instruments that record the ground’s motion when an earthquake occurs. The first seismograph was developed in 1890.

Seismograms

Images of the ground trembling at the precise location where the sensor is positioned are called seismograms. On a seismogram, the horizontal axis shows time (measured in seconds) while the vertical axis reflects ground movement (usually measured in millimeters).

Also read: Causes of Tsunami here for UPSC Geography Preparation.

Role of the National Centre for Seismology

• The National Center for Seismology is the main government organisation in India responsible for monitoring earthquake activity (NCS).
• The National Seismological Network, under the direction of NCS, consists of more than 150 contemporary seismic stations all over the country.
• The NCS continuously monitors seismic activity across the country, seven days a week, 24 hours a day i.e. 24 x 7.
• In addition, by setting up a temporary observatory close to the affected area, NCS also keeps an eye on earthquake swarms and aftershocks.
• NCS has a big role to play in the micro zonation of seismic hazard and seismological research in addition to recording earthquakes.

Some other activities of the NCS include

• Upkeeping the information services and seismic data centre.
• Studies on seismic hazard microzonation.
• Earthquake monitoring and aftershock surveys using swarms.
• To know how the earthquake occurred and predict future earthquake events in the area.

List of Seismograph Centres in India

Seismic Waves

• When materials unexpectedly move within the Earth, such as when they slide down a fault during an earthquake, seismic waves are produced.
• Seismic waves can be produced by landslides, avalanches, explosions, volcanic eruptions, and even swiftly moving rivers. Seismometers can record the images of seismic waves as they move through and around the Earth.
• Seismic waves are of two types Body waves and surface waves.
  • Body waves are those waves which travel through the Earth i.e through the body of Earth and are two types P waves and S waves.
  • Surface waves frequently move across the surface of the Earth’s crust more slowly than body waves because they have a lower frequency.

Surface Waves

A seismogram may show that these waves are distinct. As an earthquake’s depth deepens, surface waves from shallower earthquakes get stronger. Surface waves are of two types Love waves and Rayleigh waves.

List of Famous Seismologists

Importance Of Seismology

• Seismology is one of the methods for learning anything about the internal structure of the earth from a pure and practical scientific basis.
• It can determine with good precision how the Earth’s core is split into a solid inner core and a liquid outer core with the help of the data that seismograms can provide on trip times and amplitude fluctuations.
  • The type of waves that may and cannot flow through these areas provide evidence for this. S-waves (shear waves) can only pass through solids, whereas P-waves (compressional waves) can travel through both liquid and solid materials.
• Additionally, by keeping an eye on seismic activity through the network of WWSS (Worldwide Seismological Stations), it can figure out where earthquakes originate, their depth, and what their focal mechanisms are.
• Seismology has many practical uses in society. Site surveys for significant infrastructure, such as dams and bridges, are one of its most popular applications.
• Shallow engineering seismology investigations are carried out to ascertain the near-surface geology’s capacity to support the huge loads that hydro dams, bridge pillars, etc.
• The likelihood of an earthquake of a certain size that could severely damage such a crucial facility is taken into consideration when determining whether a site is suitable for a nuclear power station.
• Passive seismic monitoring has recently been used to locate earthquakes connected to the extraction of oil and gas resources and caused by human activity.

Conclusion

Seismologists can use seismology to follow the arrival of seismic waves at seismic stations all over the world in order to gain a better understanding of the internal structure of the Earth. For example, they can draw the conclusion that the Earth’s outer core is liquid as s-waves cannot traverse it. The Earth’s seismic waves follow curved pathways (because of the increasing pressure, materials are denser towards the core, travel velocity of seismic waves increases). Seismic waves vary from their intended path due to refraction. When they strike some surfaces at an abnormally shallow angle, they reflect off of them (like the core-mantle barrier).

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