Richter and Mercalli Scales: Differences, Tables, Examples
The Richter scale measures an earthquake's magnitude (the energy it releases) as a single number, such as 5.8; the Mercalli scale measures intensity, meaning how strongly the shaking was felt and what damage it caused in a given place, in Roman numerals from I to XII. One earthquake has a single magnitude but many intensities, depending on distance, depth and ground conditions. Today seismologists report moment magnitude (Mw), which replaced Richter for large earthquakes even though the news still says “Richter.”
Magnitude table (Richter / Mw)
Magnitude is a decimal number, and it is the same for everyone wherever they are. The scale is logarithmic: every step up multiplies the wave amplitude by 10 and the energy released by about 32. A magnitude 7.0 earthquake releases roughly 1,000 times the energy of a 5.0.
| Magnitude (Mw) | Class | Typical effects | Approx. frequency worldwide (per year) |
|---|---|---|---|
| Less than 3.0 | Very minor | Recorded by instruments; almost never felt. | over a million |
| 3.0–3.9 | Minor | Often felt, but rarely causes damage. | ~130,000 |
| 4.0–4.9 | Light | Objects and windows rattle; damage is unlikely. | ~13,000 |
| 5.0–5.9 | Moderate | Can damage vulnerable buildings near the epicenter. | ~1,300 |
| 6.0–6.9 | Strong | Can be destructive in populated areas within tens of kilometers. | ~130 |
| 7.0–7.9 | Major | Serious damage over large areas. | ~15–17 |
| 8.0 or more | Great | Devastating damage across hundreds of kilometers. | ~1 |
Classes and frequencies: commonly used indicative values (approximate worldwide averages, in line with USGS statistics). Effects are indicative: they depend on focal depth, distance and construction quality.
Modified Mercalli scale (I–XII)
Mercalli intensity is not measured with instruments: it is assigned from what people felt and the damage observed. That is why it changes from place to place for the same earthquake: it can be VIII near the epicenter and barely III hundreds of kilometers away. Earthquakes are frequent in South America because the Nazca plate sinks beneath the South American plate (more in Tectonic Plates in South America).
| Degree | Perceived shaking | What is felt and what damage occurs |
|---|---|---|
| I | Not felt | Detected only by instruments. |
| II | Weak | Felt by a few people at rest, especially on upper floors. |
| III | Weak | Noticeable indoors, especially on upper floors; many do not recognize it as an earthquake. Feels like a passing truck. |
| IV | Light | Felt by many indoors and a few outdoors; dishes, windows and doors rattle; some people wake up at night. |
| V | Moderate | Felt by almost everyone and many wake up; some objects fall or break. |
| VI | Strong | Felt by all and many are frightened; heavy furniture moves; plaster falls and damage is slight. |
| VII | Very strong | Hard to stand; slight to moderate damage in well-built structures and considerable damage in poorly built ones; some chimneys break. |
| VIII | Severe | Considerable damage in ordinary buildings, with partial collapse; chimneys, columns, monuments and walls fall. |
| IX | Violent | Heavy damage even in well-designed structures; buildings shift off their foundations; visible cracks in the ground. |
| X | Extreme | Some well-built wooden structures and most masonry and frame structures are destroyed; landslides and bent rails. |
| XI | Extreme | Few masonry structures remain standing; bridges are destroyed; wide cracks open in the ground. |
| XII | Extreme | Total destruction; the ground surface deforms and objects can be thrown into the air. |
Which intensity matches which magnitude?
There is no fixed equivalence between magnitude and intensity: intensity depends on the distance from the rupture area, on depth and on the soil. As a rough guide, near the epicenter a magnitude 4 to 5 earthquake is usually felt at intensity IV–V, one of 5 to 6 at V–VII, one of 6 to 7 at VII–IX and one of 7 or more at VIII or higher.
Richter or “Ritcher”? Today seismologists use moment magnitude (Mw)
It is spelled Richter (R-i-c-h-t-e-r): the “ch” comes before the “t.” “Ritcher” is a common misspelling. The name belongs to Charles F. Richter, the seismologist who proposed the scale in 1935 to measure earthquakes in California.
The original scale (local magnitude, ML) has a limit: for earthquakes near magnitude 6.5–7 it stops reflecting the true size of the event. That is why, since the late 1970s, seismologists use moment magnitude (Mw), which is calculated from the seismic moment (the size of the fault that ruptured, how far it slipped and the stiffness of the rock) and stays reliable for the largest earthquakes. It is the figure published by the USGS and many national seismic networks; the media still call it “Richter” out of habit.
In practice the difference for you is small: Mw is read just like Richter, and the table above works for both. Some Mw examples according to the USGS: Valdivia (Chile, 1960), 9.5, the largest earthquake ever recorded; Tohoku (Japan, 2011), 9.1; Maule (Chile, 2010), 8.8.
Differences between Richter and Mercalli
| Aspect | Richter / Mw (magnitude) | Mercalli (intensity) |
|---|---|---|
| What it measures | The energy released by the earthquake | The effects on people, buildings and the ground |
| How it is obtained | With seismographs | From observations, witness reports and damage |
| How it is written | Decimal number (5.8) | Roman numeral (VII) |
| Values per earthquake | Just one | One per location |
| What it is for | Comparing earthquakes with each other | Assessing damage and organizing the response |
A trick to remember it
- Richter = Recorded by instruments: one number with a decimal point (6.3), the same everywhere.
- Mercalli = Mapped from what people felt and the damage: a Roman numeral (VII) that changes from place to place.
- If you see a decimal, it is magnitude; if you see a Roman numeral, it is intensity.
Frequently asked questions
What is the difference between the Richter scale and the Mercalli scale?
Richter (today, Mw) measures magnitude: the energy of the earthquake, as a single number. Mercalli measures intensity: the effects at each location, from I to XII. One is for comparing earthquakes; the other tells you their impact.
Does the Richter scale go from 1 to 10?
It has no theoretical upper limit. “1 to 10” is a common simplification, but the scale is open-ended; the largest earthquake ever recorded reached Mw 9.5 (Chile, 1960). The 12 degrees belong to the Mercalli scale.
What does a magnitude 4.5 earthquake feel like?
Near the epicenter it is clearly felt, with intensities around IV–V on the Mercalli scale: objects and windows rattle and it can wake sleeping people, but it rarely causes significant damage. If it is deep or far away, it is felt less.
Why does each agency report a different magnitude for the same earthquake?
Each network processes its own data, and first estimates are revised in the following hours. Differences of a tenth or two between agencies are normal; look at the most recent update.
Can earthquakes be predicted?
No. Today it is not possible to say precisely when, where or how large an earthquake will be. What you can do is get ready: put together a seismic emergency kit and learn what to do during and after an earthquake.
How to find out about a nearby earthquake
Vigía, the alerts feature of Contingencias Premium, notifies you of earthquakes of magnitude 4.5 or higher within 100 km (about 60 miles) of your city or field (these are the starting values, and you can change them). It is an after-the-fact notice: it arrives once the earthquake has been recorded, it does not anticipate it. Learn about Vigía. To understand how these earthquakes are recorded, read How Earthquakes Are Measured.
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