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# Earthquake Calculator

Richter scaleMoment magnitude scaleModified Mercalli intensity scaleEarthquake calculator – how to useMost powerful earthquakesWarning, earthquake! What to do during an earthquake?

With this earthquake calculator, you can estimate the energy release of an earthquake. We understand that enormous energy values expressed in joules are not very intuitive or informative, so we have chosen a few earthquake energy equivalents — if you've ever wondered what magnitude of earthquake an atomic bomb 💣 or volcanic eruption 🌋 is equivalent to, this earthquake magnitude calculator has the answer. Also, our tool is a safe bet if you want to compare different earthquakes and want to know how much stronger one earthquake is compared to another.

In the article below, you'll learn about the different measures of an earthquake: from the famous Richter scale to the currently used moment magnitude scale and Mercalli scale, which is an intensity scale describing the effects of the phenomenon. Play with the tool to contemplate and admire Mother Earth's natural strength, or scroll down to read about the most powerful earthquakes the world has ever seen.

## Richter scale

Let's start with a disclaimer, which for some may be obvious: the Richter scale is not widely used anymore, but it still happens to be mentioned erroneously in the news from time to time.

The Richter magnitude is based on the wave amplitude recorded by seismographs. Charles Richter developed the logarithmic scale in 1935 to compare local earthquakes – the ones in southern California with an epicenter of up to 370 miles (600 km) from the seismograph. Apart from the fact the scale was intended to be for a specific area only, seismographs from that period weren't as sensitive as they are today – they could measure only certain frequencies, meaning that low frequencies were lost, and large earthquakes were underestimated.

The most important thing to remember is the fact that in the Richter scale, wave amplitudes are taken into account.

## Moment magnitude scale

If you're listening to the news about an earthquake, the measure that will be given is the magnitude — the moment magnitude to be exact. Nowadays, the moment magnitude scale is the most commonly used system. The strongest earthquake ever recorded – the one in Chile in 1960 — was 8.6 on the Richter magnitude scale but had a moment magnitude of ~9.5.

Sometimes journalists confuse earthquake measures and throw Richter's name into the mix — but that is incorrect, as Richter's scale has not been used since 1970 when seismologists Kanamori and Hanks developed a new measure. Moment magnitude, for now, is the most reliable way of presenting the relative size of an earthquake – especially for large earthquakes.

To calculate the moment magnitude, seismologists need to know the seismic moment, $M_0$:

$M_w = \frac{2}{3}\log (M_0) - 10.7$

The seismic moment is found by multiplication of three physical parameters – rigidity, area, and slip:

$M_0 = \mu AD$

where:

• $\mu$ — Shear modulus of the rocks (dyne/cm²), which is the rock's resistance to bending (rock rigidity). It is constant for specific types of rock;

• $D$ — Average fault displacement (cm); the distance one block is relocated; and

• $A$ — Area of the fault rupture (cm²), which is the estimated area over which the earthquake has occurred.

$A$ and $D$ are calculated thanks to complex mathematical models predicted by seismograms.

🙋 Earthquakes aren't the only phenomena whose magnitudes are expressed using a logarithmic scale — this is also the case for cyclones. Feel free to visit the log calculator if you feel like you could use a refresher.

The earthquake magnitude you hear just after the phenomenon has occurred may differ from the final, official values provided later (up to ±0.5). That's because the first approximations are based on body-wave and surface-wave scales, as the calculation of the moment magnitude is more complicated.

To know more about this fascinating topic, make sure to check out this excellent video by IRIS Earthquake Science –

To sum up, in the moment magnitude scale, the strength of the earthquake is tied up with the seismic moment, which depends on three physical parameters – rigidity, area, and slip.

## Modified Mercalli intensity scale

A modified Mercalli intensity scale is used to quantify the earthquake's effects. That's why you — although the released energy, local geology, terrain, depth of an earthquake and distance from the epicenter are all still the same. Thus, the Mercalli scale describes how the earthquake affected a given location, and a range of Mercalli intensity values are assigned for the same earthquake, assuming it affected not just one area.

Mercalli intensity

Observations

I

Microearthquakes, usually not felt. Recorded by seismographs.

II

Felt by a few people, especially on the upper floors.

III

Noticeable indoors, especially on upper floors. May not be recognized as an earthquake.

IV

Felt by many indoors, few outdoors. May feel like a heavy truck passing by. Dishes, windows, doors disturbed.

V

Felt by almost everyone, wakes many. Small objects moved. Trees and poles may shake. Pendulum clocks may stop.

VI

Felt by nearly everyone. Difficult to stand. Some heavy furniture moved, some plaster falls. Slight structural damage.

VII

Slight to moderate damage in well-built, ordinary structures. Considerable damage to poorly built structures. Some walls may fall.

VIII

Considerable damage to ordinary buildings, severe damage to poorly built structures. Some walls collapse.

IX

Considerable damage to specially built structures, buildings shifted off foundations. Ground cracked noticeably. Landslides.

X

Most masonry, frame structures, and their foundations destroyed. Ground badly cracked. Landslides. Wholesale destruction.

XI

Total damage. Few structures standing. Bridges destroyed. Wide cracks in ground. Rails bent greatly. Waves seen on ground.

XII

Total damage. Waves seen on ground. Objects thrown up into the air.

## Earthquake calculator – how to use

Thanks to this earthquake calculator, you can:

• Check the approximate energy release of an earthquake in energy release equivalents (such as tons of TNT, atomic bomb energies, and volcanic eruptions).

• Use it as the earthquakes' magnitude calculator to compare two earthquakes' magnitudes.

Let's test it!

1. You may have heard that a 5.8 earthquake hit Alaska recently. You may be wondering – how "big" is that? Type the value into the earthquake magnitude box.

2. And that's it! The earthquake magnitude calculator shows not only the energy but also some energy equivalents for the given magnitude:

• The released energy is 31622776601684 J, and the equivalent of such energy is:
• 7,558 t of TNT 🧨
• 0.5 Hiroshima bombs 💣
• 0.38 Nagasaki bombs 💣
• 0.0001326 Tsar bombs ☢️
• 0.000038 Krakatoa eruptions 🌋
• 0.0000028 of the most massive earthquake recorded, Chile '60 🌎

Also, by typing "1" into any field in the "Energy release equivalent" section, you can check what's the equivalent magnitude for a chosen energy release event – for example, one Nagasaki bomb released the energy of a 6.1 magnitude earthquake!

The other thing you can do with this tool is to compare two magnitudes. Let's assume that you remember an earthquake a couple of years ago, which has a magnitude of 7.1. How much bigger was it?

1. Enter the two magnitudes you want to compare – for our example, these are 5.8 and 7.1.
2. We find out that a magnitude of 7.1 is 20 times bigger (on a seismogram, in terms of amplitudes) and ~89 times stronger (in terms of energy release) than a 5.8 magnitude.

Remember that for each unit increase in magnitude:

• The amplitude of shaking is 10 times larger.
• The earthquake "size" — which is the energy released — is 32 times larger!

So, for example, an earthquake with a magnitude of 7 releases over 1000 times more energy than a magnitude 5 earthquake. You may want to check this illustrating the incredible differences between different historical earthquakes.

To calculate the amount of released energy from an earthquake, we've implemented Gutenberg and Richter's equation in this earthquake calculator:

$E = 10^{1.5 M + 4.8}$

which is sometimes expressed as:

$\log E = 4.8 + 1.5 M$

or:

$M = \frac{2}{3} \log E - 3.2$

## Most powerful earthquakes

The most powerful earthquake ever recorded happened in Chile in 1960. It occurred in the afternoon, lasted for 10 minutes, and caused tsunamis that affected southern Chile, Hawaii, Japan, the Philippines, New Zealand, Australia, and the Aleutian Islands. It also triggered numerous landslides, floods, and even volcanic eruptions.

Rank

Magnitude

Location

Date

1

9.4-9.6

Valdivia, Chile

May 22, 1960

2

9.2

March 27, 1964

3

9.1-9.3

Indian Ocean, Sumatra, Indonesia

December 26, 2004

4

9.1

Pacific Ocean, Tōhoku region, Japan

March 11, 2011

5

9.0

Kamchatka, the Soviet Union

November 4, 1952

6

8.5-9.0 (est.)

Kamchatka, Soviet Union

August 13, 1868

7

8.7-9.2 (est.)

January 26, 1700

8

8.8 (est.)

April 2, 1762

9

8.8 (est.)

Sumatra, Indonesia

November 25,1833

10

8.8

January 31, 1906

11

8.8

Offshore Maule, Chile

February 27, 2010

12

8.7

Assam, India, Tibet, China

August 15, 1950

Did you notice that 3 out of the 12 most powerful earthquakes were in Chile? The next six strongest Chilean earthquakes would be found in the top 30 most massive earthquakes by magnitude.

If you want to know , it depends on what you really mean:

1. Chile has a lot of powerful earthquakes.

2. Indonesia lies in a very active seismic region and is a relatively big country, so it probably has the most earthquakes in total.

3. Japan, however, is the country where we detect the most earthquakes (because of its dense seismic grid).

4. Tonga, Fiji, or another island country in the Pacific probably has the most earthquakes when it comes to earthquakes per area.

5. China, Iran, and Turkey lead in the category of the most catastrophic earthquakes (damages, fatalities, etc.).

Do you know that the shockwave originated from the detonation of the Tsar Bomba circled the world three times, touching at the antipodal point of the explosion and "bouncing" back?

🔎 Although in the Northern Hemisphere, antipode usually refers to Australia or New Zealand. It's actually a much broader term. Check out the antipode calculator to learn more!

## Warning, earthquake! What to do during an earthquake?

If you're interested in the latest earthquakes in your region or only the most recent earthquakes (as they are happening all the time!), check out this .

Also, it's essential to make sure that you know what to do during an earthquake before you're caught in one. Depending on where you are, different recommendations exist:

1. I'm inside 🏠

Stay there! The most important rules to remember are drop, cover, and hold on:

• Drop to the ground onto your hands and knees.

• Using one arm, cover your head and neck. Crawl under a sturdy table/desk if nearby.

• Hold on to your shelter with one hand until the shaking stops. In case of no shelter, hold on to your head and neck with both arms and hands.

🔎 There are many ways of protecting buildings from earthquakes, such as friction pendulums — you can read about them in the article accompanying the damping ratio calculator.

1. I'm outside🏙️

Get to an open space if possible. Avoid buildings, trees, power lines, and signs if you can. Then drop, cover, and hold on, as objects may be thrown at you from the side.

2. I'm driving 🚘

Pull over, stop, and engage the handbrake. Don't stop under bridges, overpasses, trees, or power lines. Stay inside until the shaking stops.

Some things that shouldn't be done:

• Don't hide in a doorway.
• Don't run, don't run outside.
• Don't use lifts.