Earthquake Magnitude vs Intensity: What Is the Difference?

By Nesim Razon, independent Android developer · 2026-11-10

After every earthquake you hear two words: magnitude and intensity. People often use them as if they meant the same thing, but they answer different questions. Magnitude asks how big the earthquake was. Intensity asks how strongly it was felt in a particular place.

Magnitude: one number for the earthquake

Magnitude describes the size of the earthquake at its source. It is calculated from instrument records, called seismograms, and it does not depend on who is standing where. A single earthquake has one true magnitude, whether you sit next to the fault or on the other side of the country.

In practice, each agency computes its own estimate from the stations it has, so you may see slightly different values for the same event. That is normal and is explained in a separate article about where earthquake data comes from. The important point here is that magnitude is a property of the earthquake, not of the place that felt it.

Richter, ML and moment magnitude

The first widely used scale was proposed by Charles Richter in 1935 for earthquakes in southern California. It is based on the largest amplitude recorded by a particular type of seismograph, corrected for distance. Today it is usually called the local magnitude and written ML. People still say 'Richter scale' in everyday speech, even when the number was calculated another way.

Local magnitude works well for small and moderate earthquakes at short distances, but for very large earthquakes it stops growing as fast as the real size of the event. Seismologists call this saturation. For that reason the moment magnitude, written Mw, became the standard for larger earthquakes. Mw is calculated from the seismic moment, which depends on the area of the fault that slipped, how far it slipped and the stiffness of the rock. Because it does not saturate, it describes great earthquakes much more reliably.

Other magnitude types exist too, for example a duration magnitude (MD) that uses how long the shaking lasts on a record, and magnitudes based on body waves or surface waves. All of them are designed to land close to each other for typical events, but they can differ by a few tenths.

The scale is logarithmic

Magnitude scales are logarithmic, so each whole step is a multiplication, not an addition. One unit of magnitude means the ground motion recorded on a seismogram is about 10 times larger. In terms of released energy, one unit is about 32 times more, because energy grows faster than amplitude.

A magnitude 6.0 earthquake therefore releases about 32 times the energy of a magnitude 5.0, and roughly 1000 times the energy of a magnitude 4.0. Two units mean about 100 times the amplitude and about 1000 times the energy. This is why a difference of 0.5 or 1.0 in a news report is a very big difference, and why many small earthquakes cannot add up to release the energy of one large one.

Intensity: what people and buildings experience

Intensity describes the effects of shaking at a specific location: whether people feel it, whether objects fall, whether buildings are damaged. It is not measured by one instrument but assigned by looking at effects, using scales such as the Modified Mercalli scale or the MSK and European Macroseismic scales. These use Roman numerals, usually from I (not felt) to XII (total destruction).

Because intensity belongs to a place, one earthquake produces many different intensity values: high near the epicenter and lower farther away. Maps that show these values for one event are made from reports and observations and are different from a map of epicenters.

Why the same earthquake feels different

• Distance: shaking weakens as seismic waves travel away from the source.
• Depth: a shallow earthquake usually shakes the surface harder than a deep one of the same magnitude.
• Ground: soft soil and sediment can amplify shaking, while hard rock tends to shake less.
• Buildings: the quality of construction and the building height affect how much damage the same shaking causes.
• Duration and direction: how long the shaking lasts and how the fault ruptures also change what people feel.

A worked example

Compare a magnitude 5.0 earthquake with a magnitude 7.0 one. The difference is two units, so the recorded ground motion of the larger one is about 100 times bigger and the energy released is about 1000 times greater. The larger earthquake also ruptures a much larger part of the fault, which is why great earthquakes shake wide regions for a long time, while a magnitude 3 may be felt only by a few people close to the epicenter.

This also shows why saying that a magnitude 8 is twice a magnitude 4 is wrong. The numbers are exponents of a scale, not quantities you can divide.

Common misunderstandings

• The scale has no printed top, but real earthquakes are limited by the size of the faults that exist, so there is a practical maximum.
• Very small earthquakes can have magnitudes near zero or even below zero; they are recorded by instruments but felt by nobody.
• A high magnitude does not automatically mean heavy damage in a given city, and a moderate magnitude can still be damaging if it is shallow and close to buildings that are weak.
• Intensity values are not a second opinion about magnitude; they are measuring something else.

Reading an earthquake list

When you look at a list of recent earthquakes, the number you see is a magnitude, and the list usually shows depth too. A magnitude 3.5 at 10 km depth under your town might feel like a short jolt, while a magnitude 5.5 far offshore might be barely noticed on land. Magnitude tells you how large the event was; depth, distance and local conditions tell you how likely you were to feel it.

A list in an app such as Son Depremler shows magnitude, depth, time and location for each earthquake, so you can compare them side by side. It is a source of information, not a warning system. For official information and safety advice after a strong earthquake, follow AFAD.