How Does the Richter Scale Measure an Earthquake?


Earthquakes are geological hazards which occur due to the movement of tectonic plates in the Earth's crust. Their study requires specific tools and scales to measure their magnitude, intensity and effects. The Richter scale is a method that measures the energy released at the epicenter of an earthquake using records obtained by seismographs. In this article from thedailyECO, we ask how does the Richter scale measure an earthquake? To answer our question, we look at the scales, degrees and tools which are used to measure the Richter scale.
What is the Richter scale?
The Richter scale is a system used to measure the magnitude of earthquakes. It was developed in 1935 by Charles F. Richter, an American seismologist. It is based on recording the energy released during an earthquake. The measurement is made with an instrument called a seismograph which detects seismic waves generated by the movement of tectonic plates.
This Richter scale uses a logarithmic system, meaning that each one-point increase represents a tenfold increase in the amplitude of seismic waves and approximately 31.6 times more energy released. For example, a magnitude 6 earthquake is significantly more powerful than a magnitude 5 earthquake, but a magnitude 2 is not as greatly different when compared to a magnitude 1.
Although the Richter scale was widely used in the past, it has now been largely superseded by other scales such as the moment magnitude scale. These advancements provide a more accurate measurement, especially for large earthquakes. Despite this, the Richter scale is still known to the public and is used as a reference for understanding the intensity of earthquakes.
Discover more about what earthquakes are and how they occur in our related guide.
Degrees on the Richter scale
The Richter scale is used to classify the magnitude of earthquakes based on the amount of energy they release. Although the scale has no upper limit, in practice earthquakes often reach magnitudes of up to 9 or just above. The following are the gradations of the Richter scale and the effects of their corresponding earthquakes:
- Less than 2.0: micro-earthquakes that are almost never felt by people. They occur constantly around the world, but are only detected by seismographs.
- 2.0 to 3.9: mild earthquakes that rarely cause damage. People sometimes perceive them as a slight vibration, especially if they are close to the epicenter.
- 4.0 to 4.9: these earthquakes are moderate. They can shake objects and, in rare cases, cause minor damage to poorly constructed structures.
- From 5.0 to 5.9: these are earthquakes of considerable magnitude. They can cause slight to moderate damage to buildings, especially in areas close to the epicenter or in older structures.
- 6.0 to 6.9: earthquakes in this category can cause severe damage in populated areas. Weak or poorly designed buildings often collapse, while stronger ones may show cracks or minor damage.
- 7.0 to 7.9: these are major earthquakes that can cause significant destruction, especially in densely populated areas. Damage varies depending on the quality of buildings and the preparation of the affected area.
- 8.0 and above: these are catastrophic earthquakes. They can devastate entire regions, causing serious human and property losses and ground disturbances. Historical examples include earthquakes such as the one in Valdivia (Chile) in 1960, which had a magnitude of 9.5, the largest ever recorded.
The magnitude of an earthquake should not be confused with its intensity, as the latter measures how the earthquake is felt at a specific location. It depends on factors such as distance from the epicenter and soil characteristics.
To highlight the true destructive force of these geological phenomena, read our article explaining the biggest earthquakes in history.

How does the Richter scale measure an earthquake?
Earthquake measurement combines the use of specialized tools and different scales to assess their magnitude, intensity and effects. Once the measurements are taken, they can be graded against the scale to provide the Richter reading. The tools used to carry out this process include:
- Seismograph: this is the main instrument for recording earthquakes. It works by detecting ground vibrations produced by seismic waves. It consists of a sensor known as a seismometer which is connected to a recording system that draws a seismogram, a graph showing the amplitude and frequency of the waves.
- Accelerograph: similar to a seismograph, but designed to measure more intense and rapid movements such as those occurring near the epicenter. It is especially used to assess impacts on urban structures.
- Seismological networks: consist of interconnected seismological stations that allow the epicenter to be located and the magnitude of the earthquake to be calculated with greater precision. These networks operate at both regional and global levels.
Once we know what tools are used to measure seismic activity, these measurements can be compared against different scales. The scales to measure earthquakes include the following:
- Richter magnitude scale: we have already seen that it measures the energy released by the earthquake at its epicenter, being useful for small and medium earthquakes.
- Moment magnitude scale (Mw): this is currently the most widely used scale in seismology. It calculates the total energy released by considering factors such as rupture area, fault slip and rock stiffness. It is especially accurate for large earthquakes.
- Modified Mercalli Intensity Scale (MMI): measures how the earthquake is felt and the damage caused in a specific area. It ranges from I (imperceptible) to XII (total destruction). It is subjective, as it is based on human observations and structural damage.
- European Intensity Scale (EMS-98): similar to the Mercalli scale, but designed specifically to assess effects on European structures. It also classifies damage from I to XII.
- Local magnitude (ML) scale: a variant of the Richter scale for measuring small, local earthquakes. It is mainly used in specific studies.
- Surface magnitude scale (Ms) and body wave scale (Mb): these evaluate different types of seismic waves. Ms measures surface waves, while Mb focuses on the planet's internal waves. Both are used as complements to characterize earthquakes.
Learn more about how tectonic movement affects global ecosystems with our article explaining the difference between an earthquake and a tremor.

Differences between the Richter and Mercalli scales
The main difference between the Richter scale and the Mercalli scale is what they measure and how these results are interpreted. The Richter scale measures the energy released by an earthquake at its epicenter and is based on records obtained by seismological instruments. In comparison, the Mercalli scale evaluates the visible and perceptible effects of an earthquake in a specific area.
It can be said that the Richter scale is used to measure the magnitude of an earthquake and that the Mercalli scale is used to measure the intensity of its effects. If we use an example with both scales, we would see how an earthquake of magnitude 6 in an urban area with fragile buildings could cause damage classified as intensity VIII (severe), while the same earthquake in an uninhabited region could not exceed degree IV (mild). The Richter scale uses quantitative and objective data, while the Mercalli scale uses more qualitative data.
Now that you know what the Richter scale is, you may also be interested in our article explaining the different types of seismic waves.
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- Diego Navarro. (2023). What is the Richter scale and why it is incorrect to use it in large-magnitude earthquakes.
https://www.newtral.es/escala-richter-terremotos/20230210/ - FundéuRAE. (2010). Earthquakes: Richter scale and Mercalli scale.
https://www.fundeu.es/recomendacion/terremotos-escalas-de-medicion-2/ - Francisco Navarro. Earthquakes. How are they measured and what are the main scales? INESEM.
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