During an earthquake, the size of the actual earthquake and the actual shaking of the ground are two different factors that determine the impact of the earthquake.
Oftentimes, people get confused and use both terms to emphasize the same thing when both are distinct factors that evaluate two different aspects.
Key Takeaways
- Magnitude measures the size or strength of a phenomenon, while intensity measures the degree of impact or effect of the phenomenon.
- Magnitude is measured on a logarithmic scale, while intensity is measured on a linear scale.
- Magnitude is used to measure earthquakes and other natural disasters, while intensity measures the effects of these disasters on human lives and structures.
Magnitude vs Intensity
Magnitude represents the energy released at the earthquake’s source, measured using logarithmic scales like Richter or Moment Magnitude scales. Intensity, on the other hand, quantifies the effects of an earthquake at specific locations, considering factors like damage to structures, ground shaking, and human perception.
Magnitude is a common term used in geology to describe the actual size of an earthquake. It is sometimes also used to measure the energy that the earthquake produces.
A device called the Seismograph is used to measure an earthquake’s magnitude. The device produces waves or lines on a sheet of paper when the ground on which it is placed begins to shake.
Intensity is the measurement of the actual strength of an earthquake. The strength of the earthquake is measured in terms of the actual damage caused by the shaking.
Intensity varies from the perception of people, animals, and other aspects such as property damage, structural damage, natural surroundings, and so on.
Comparison Table
| Parameters of Comparison | Magnitude | Intensity |
|---|---|---|
| Definition | Magnitude is the measurement of the size of an earthquake | Intensity is the measurement of the strength of the earthquake |
| Measured by | To measure the magnitude of the earthquake, a seismograph is used | The intensity is measured by calculating the damage caused by the earthquake |
| Value | The magnitude value of an earthquake is a single number on the Richter scale. | The intensity value is represented as a roman capital ranging from I to XII in the Modified Mercalli Intensity (MMI) scale. |
| Uses | Magnitude calculates the radius of the earthquake | Intensity values are used to design structures and buildings |
| Levels | An increase in magnitude level indicates a 10 times stronger earthquake | The intensity levels decrease from the epicentre of the earthquake |
What is Magnitude?
Magnitude is a common term used in geology to describe the size of an earthquake. The size of the earthquake describes the potential radius of damage because of the earthquake.
Magnitude is also sometimes used to measure the energy of the earthquake, as earthquakes with more energy have a greater size and produce greater damage.
The magnitude is measured using a device called the seismograph. It is a pin and sheet arrangement where a highly sensitive pin is suspended over a paper or graph. The device is highly sensitive to any shaking produced.
When the device is placed on earthquake-prone land, the needle of the device will shake in the event of shaking of the ground. The shaking of the needle produces waves or lines on the graph sheet.
Thus depending on the shaking energy, the waves produced will have greater amplitude and frequency. Thus with greater magnitude, more waves will be produced.
This is used as a factor to determine the impact of the earthquake, as with greater magnitude, greater potential damage will be produced.
The magnitude is calculated using the Richter scale, which is a logarithmic approach to reading the amplitude of the graph produced in the seismograph.
What is Intensity?
Intensity is a measurement of the actual strength of an earthquake. The strength is measured in terms of the damage caused by the shaking. This accounts for all the various types of damages produced in a region.
In geology, intensity is a common term to describe the shaking produced in a given region by an earthquake. A strong earthquake produces more damage and thus has greater intensity.
Intensity is measured using the Modified Mercalli Intensity (MMI) scale, which modifies the Rossi-Forel scale. The scale assigns a roman capital numeral to the intensity of the earthquake.
The scale ranges from I (least perceptive damage) to XII (maximum perceptive damage). As the intensity measurement depends on the perceived damage, the intensity varies on the amount of damage produced in a region.
Thus the intensity varies from region to region, decreasing from the epicentre of the earthquake. Epicentre is the region that is directly hit by the earthquake.
Depending on the magnitude, the shaking spreads to neighbouring regions from the epicentre.
Thus low-intensity shaking is observed in the neighbouring regions of the epicentre. The perceived damage accounts for all types of damages observed in the earthquake that hit the region.
These include property damage, damage to natural surroundings, structural damage, and so on.
Main differences Between Magnitude and Intensity
- Magnitude is a measurement of the size of an earthquake. Intensity is the measurement of the actual strength of the earthquake.
- Magnitude is measured using a seismograph. Intensity is calculated from the perceived damage caused by the earthquake.
- The magnitude is represented as a single number on the Richter scale. The intensity value is represented as a roman capital on the MMI scale
- The magnitude value calculates the radius of the impact of an earthquake. Intensity values are used in design calculations of bridges, buildings and other structures
- An increase in magnitude level indicates a 10 times stronger earthquake. The intensity level decreases from the epicentre of the earthquake.
- https://pubs.geoscienceworld.org/geology/article-lookup/7/7/336
- https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JB082i020p02981
- https://link.springer.com/content/pdf/10.1007/978-3-030-10475-7_23-1.pdf
- https://sjg.springeropen.com/articles/10.1007/s00015-012-0095-3
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