Richter Scale - Meaning, Measurement of Earthquakes and Important Facts

The Richter Scale is a quantitative measure of the Earthquake magnitude. It is also called the magnitude scale, where the energy released is measured in the range of 1-10. The Richter scale, also known as the Gutenberg-Richter scale, is a system for quantifying the intensity of earthquakes. It was created by Charles Francis Richter and introduced in his influential 1935 publication, initially referred to as the "magnitude scale." Subsequently, it underwent revision and a name change to the local magnitude scale, often denoted as ML or ML.

Richter scale is one of the most important topics for the UPSC IAS exam. It covers a significant part of Geography in the General Studies Paper-1 syllabus and Science and Technology General Studies Paper-3 syllabus. 

In this article, we shall study in detail an overview of the Richter Scale, its uses, measurement process, and Earthquakes of varying strength for the UPSC exam.

What is the Richter Scale?

Richter Scale is used to measure the magnitude of an earthquake or to measure the strength of the Earthquake or the amount of energy released during the earthquake. It was invented by American seismologist Charles F. Richter of the California Institute of Technology as a mathematical device that was used to compare the size of earthquakes in 1935.

How does the Ritcher scale Measure Earthquake?

• The magnitude of earthquakes is measured by the Richter scale.
• Earthquakes are sudden movements inside the earth where tectonic plates move against each other, which leads to the release of energy.
• Over time, this energy becomes more than the Earth can withstand. This energy is released violently and suddenly as an Earthquake.
• This energy is released in the form of seismic waves that are recorded on the seismograph.
• It is determined by the base 10 logarithm of the amplitude of waves recorded.
• This corresponds to the 31.6 times energy released for each unit level increase in magnitude.
• For example, If the magnitude of an earthquake registered at 7 on the Richter scale means its magnitude is 10 times the earthquake on the Richter scale 6, corresponding to the 31.6 times energy released by the lesser earthquake.

Study the Article Tsunami here!

Magnitudes on a Richter Scale

Earthquakes are classified according to their varying strength, as mentioned in the following table:

Classification	Magnitude(moment scale)	Effects of Earthquake	Frequency of occurrences
Micro	1-1.9	Earthquakes of very low intensity, rarely felt. Seismograph records them	Several million per year
Minor	2-2.9	Slightly felt to some people. Causes no damage.	Over one million per year
	3-3.9	Rarely causes damages ,often felt by people. Noticeable shaking of indoor objects.	Over 100,000 per year
Light	4.0–4.9	Noticeable shaking of indoor objects Felt to most people in affected areas. Causes none to minimal damage. Some objects may be knocked over or fall off shelves	10,000 to 15,000 per year
Moderate	5.0–5.9	Poorly constructed buildings are severely affected while other buildings remain unaffected. Felt by everyone.	1,000 to 1,500 per year
Strong	6.0–6.9	Moderate number of well-built structures are damaged in populated areas. Well built and earthquake resistant structure survives from slight to moderate damage. Severe damage to poorly built structures. Its range extends to hundreds of kilometers from the epicenter. Epicentral area to have strong to violent shivering.	100 to 150 per year 2011 Christchurch earthquake (6.2)
Major	7.0–7.9	Severe damage is caused to most of the structures from partially to full collapse. Even well-designed structures may suffer damage. It is felt across large distances with major damage limiting to 250km from epicenter.	10 to 20 per year 1819 Rann of Kutch earthquake (7.7–8.2) 2001 Gujarat earthquake (7.7)
Great	8.0–8.9	Structures suffer major damage, some of them destroyed. Even moderate to heavy damage is felt on earthquake-resistant structures. It causes destruction in large areas. Tremors are felt in extremely large regions.	One per year 1556 Shaanxi earthquake (8.0) 1950 Assam–Tibet earthquake (8.6) 2008 Sichuan earthquake (8.0) 2010 Chile earthquake (8.8)
	9.0 and greater	It cause catastrophic damages Complete destruction of all buildings. Ground topography changes permanently. Even large distant locations suffer severe damage or collapse to all buildings.	One per 10 to 50 years 1960 Valdivia earthquake, Chile (9.4–9.6) 1964 Alaska earthquake (9.2) 2004 Indian Ocean earthquake (9.1–9.3) 2011 Tōhoku earthquake, Japan (9.1)

Study the article on Biological Disaster Management here!

Earthquake Magnitude Scale

The earthquake magnitude scale is a system used to measure and quantify the size or intensity of earthquakes. There are several different scales for measuring earthquake magnitudes, with the most commonly known being the Richter scale, developed by Charles Francis Richter in 1935. The Richter scale assigns a single number to an earthquake based on the amplitude of seismic waves recorded on seismographs, which reflects the energy released during the earthquake.

In addition to the Richter scale, there are other magnitude scales used today, such as the Moment Magnitude Scale (Mw), which has largely replaced the Richter scale for large earthquakes. The Moment Magnitude Scale takes into account various aspects of an earthquake, including the fault length, fault slip, and the material properties of the Earth, providing a more accurate and consistent measure of an earthquake's size, especially for very large events.

Uses of the Richter Scale

The Richter scale measures the magnitude of the Earthquake. Charles F. Richter developed the Richter Magnitude Scale (ML). However, because of its shortcomings, seismologists are now using the moment magnitude scale (Mw), which is commonly referred to as the Richter Scale.

• The Magnitude Richter scale records the highest amplitude of the wave for calculation of magnitude.
• It has its limitations in recording beyond the magnitude of 6.5 as the values calculated after measuring large seismic waves tend to cluster or saturate.
• Hence, accurate measurement is not possible. Scientists are now using the moment magnitude (MW or M) scale.
• It was developed by Japanese seismologist Hiroo Kanamori and American seismologist Thomas C. Hanks in the late 1970s.
• It can predict earthquake total energy released more accurately.
• Instead of measuring the peak wave amplitude, an earthquake’s seismic moment (M0)(displacement of the fault across its entire surface multiplied by the force used to move the fault) is used.
• Moment magnitude continues to express earthquake magnitude using logarithmic calculations where its results compare favorably with those of other scales below magnitude 8.
• Another scale, called the Mercalli Scale, is used to measure the intensity of the earthquake.

Study the article on floods here!

Difference between the Richter Scale and the Mercalli scale

Major differences between the Richter and Mercalli scales are as follows:

Role	Richter Scale	Mercalli Scale
Purpose	It measures the magnitude of the Earthquake.	It measures the intensity of the Earthquake .
Function	It quantifies the amount of energy released during an Earthquake.	It quantifies the damages visible from earthquakes.
Range	It ranges from 1-10.	It ranges from 1-12.
Alternate names	Richter magnitude scale	Modified Mercalli scale (MM) or Modified Mercalli Intensity scale (MMI).
Developed in	1935	1884 and 1906
Inventor	Charles Francis Richter	Giuseppe Mercalli

Study the article on NDMA here!

Facts about the Richter Scale

• It records the Earthquake magnitude on a scale of 1-10.
• Richter scale is open-ended, meaning theoretically, it does not have any upper limit on the scale.
• Now, the highest magnitude of 8.6( 9.5 on the moment magnitude scale) was recorded in 1960 in Chile.
• Each unit increase in the magnitude means a 10-fold increase in earthquake magnitude.
• Every unit increase on the Richter scale means 31.6 times more release of energy to the corresponding lesser unit.

Study the article on Urban flooding in India here!

Conclusion

The advent of the modern age and various anthropogenic activities, like many instances of ruthless mining operations, construction of humongous dams, and melting of polar ice caps, disturbs the equilibrium of various forces operating deep inside the earth. Earthquake prediction and early warning systems need more refinement. However, moving from recording in the Richter scale from magnitude, to moment magnitude scale helps in more accurate measurements. There is a need to do periodic zoning of areas in a time-bound manner to keep various anthropogenic activities in check.

Study in more detail about the causes, earthquake zones, and more about earthquakes here.

Testbook provides holistic and comprehensive details about various topics for different competitive exams. Testbook is always on the top of the list because of its best quality assured products like live tests, mocks, Content pages, GK and current affairs videos, and much more. To study more topics for UPSC, download the Testbook App now!