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The Richter Earthquake Magnitude Scale

Updated on August 28, 2011

The Richter Scale Information Page

Ever wonder what the difference is between a 5.0 and a 6.0 earthquake? Well, I'll explain the difference and give you some background on the man for which it is known.

You may also wonder how to keep safe during an earthquake. I'll discuss that as much more!

The Man: Charles F. Richter

Charles Francis Richter (April 26, 1900 - September 30, 1985), was a seismologist and physicist from Ohio. Richter is most famous as the creator of the Richter magnitude scale which, until the development of the moment magnitude scale in 1979, quantified the size of earthquakes.

He worked at California Institute of Technology until 1936 when he obtained a post at the California Institute of Technology, where Beno Gutenberg worked.

While at the Carnegie Institute, Richter worked in the Seismology lab, which was hoping to begin publishing regular reports on earthquakes in southern California. However, they also needed to develop a system of measuring the strength of earthquakes for these reports. Along with Robert Millikan, Charles Richter had devised the scale that would become known at the Richter scale, which is based on measuring quantitatively the displacement of the earth due to seismic waves.

Later, Gutenberg and Richter published Seismicity of the Earth in 1941. Its revised edition, published in 1954, is still considered a standard reference in the field.

The effect of an earthquake in Nottingham, England

The effect of an earthquake in Nottingham, England
The effect of an earthquake in Nottingham, England

The Magnitude

The magnitude of most earthquakes is measured on the Richter scale using a seismometer. The Richter Scale is also known as the Local Magnitude Scale. It is calculated from the amplitude of the largest seismic wave recorded for the earthquake, no matter what type of wave was the strongest. The Richter scale can only measure accurately to about an 8.3 earthquake.

The original Richter scale was based on a particular sort of seismometer. The device consists of a secure and stable frame, a weight held in place by inertia, vibration-dampening springs to prevent long-term oscillations, and a way of measuring the displacement of the weight from the reference point.

Charles Richter:

"I like to use the analogy with radio transmissions. It applies in seismology because seismographs, or the receivers, record the waves of elastic disturbance, or radio waves, that are radiated from the earthquake source, or the broadcasting station. Magnitude can be compared to the power output in kilowatts of a broadcasting station. Local intensity on the Mercalli scale is then comparable to the signal strength on a receiver at a given locality; in effect, the quality of the signal. Intensity, like signal strength, will generally fall off with distance from the source, although it also depends on the local conditions and the pathway from the source to the point."

The Richter magnitudes are based on a logarithmic scale (base 10). What this means is that for each whole number you go up on the Richter scale, the amplitude of the ground motion recorded by a seismograph goes up ten times. So, a 5.0 earthquake is 10 times the intensity of a 6.0 earthquake on the Richter scale.

A magnitude 8 earthquake

releases as much energy as detonating 6 million tons of TNT!

Earthquake Magnitude Classes

Earthquakes are also classified in categories ranging from minor to great, depending on their magnitude.

Class and magnitude

Great 8 or more

Major 7 - 7.9

Strong 6 - 6.9

Moderate 5 - 5.9

Light 4 - 4.9

Minor 3 -3.9

"Drop, Cover, and Hold On"

"Drop, Cover, and Hold On" is the age-old mantra of protecting yourself during an earthquake.

By dropping down, covering yourself with something, and holding on to something solid, it gives you the best overall chance of protecting yourself during an earthquake... even during quakes that cause furniture to move about rooms, and even in buildings that might ultimately collapse. Dropping, covering your head (and your body by being under a strong table if possible), and holding onto furniture (even if it is moving) offers the best overall level of protection in most situations. In cases where an earthquake is less violent, you might be able to move to a more advantageous position (e.g. away from breaking windows, etc) as you drop to the floor, cover your head, and hold on to a solid object.

If there is no furniture, get next to an interior wall if possible. If you are in bed, the best thing to do is to stay where you are and cover your head with a pillow.

The idea is to protect yourself from falling objects and debris.

Interesting Facts about Earthquakes

The largest recorded earthquake in the world was a magnitude 9.5 (Mw) in Chile on May 22, 1960.

The largest recorded earthquake in the United States was a magnitude 9.2 that struck Prince William Sound, Alaska on Good Friday, March 28, 1964 UTC.

Before electronics allowed recordings of large earthquakes, scientists built large spring-pendulum seismometers in an attempt to record the long-period motion produced by such quakes. The largest one weighed about 15 tons. There is a medium-sized one three stories high in Mexico City, Mexico that is still in operation today!

A tsunami is a sea wave caused by an underwater earthquake or landslide (usually triggered by an earthquake) displacing the ocean water.

The hypocenter of an earthquake is the location beneath the earth's surface where the rupture of the fault begins. The epicenter of an earthquake is the location directly above the hypocenter on the surface of the earth.

From 1975-1995 there were only four states that did not have any earthquakes. They were: Florida, Iowa, North Dakota, and Wisconsin.

Did you know?

Because of the limitations of the Richter magnitude scale, a new, more uniformly applicable extension of them, known as moment magnitude (MW) scale for representing the size of earthquakes is being used.

A Video About Earthquakes - Brought to you by National Geographic

Books on Earthquakes

Your experiences with earthquakes?

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    • LynetteBell profile image


      6 years ago from Christchurch, New Zealand

      Actually we've just had a 4 only about 45 minutes ago. We've had over 10,000 since September 2010 Christchurch quake map

    • agoofyidea profile image


      6 years ago

      I love earthquakes. I know that sounds crazy, but I always enjoyed them when they happened in Southern California. I would try to measure them. Great lens.

    • WorldVisionary3 profile image


      7 years ago

      I've never experienced an earthquake but find them fascinating. Thanks for the informative lens!

    • profile image


      7 years ago

      Good site. Please also check this site ......

    • Michey LM profile image

      Michey LM 

      7 years ago

      Very good information lens, any bit of info make us better prepared for the future..

      Thank 5*

    • puerdycat lm profile image

      puerdycat lm 

      7 years ago

      Lens-rolled you to my brand-new christchurch-canterbury-new-zealand about the 22feb2010 earthquake. Gee I thought "earthquake" made it into the title. My little story. I'd moved cross-country and working a new West-Coast job, on my birthday, the ground shook and swayed. That might not have been enough, but nobody else batted an eyelash. We know b4 it's over? I'd rather run! With that, as beautiful as the coast is, I packed it in.

    • TonyPayne profile image

      Tony Payne 

      8 years ago from Southampton, UK

      I was on the phone once with a contact in Papue New Guinea when he said "hang on, we are having an earthquake". That was pretty astounding for me. I have seen the aftermath of earthquakes in El Salvador and Guatemala, and also in Nicaragua, where the center of the capital Managua was destroyed in the 1970s. The center remains derelect and the city has grown around it.

    • profile image


      8 years ago

      I'm so glad I haven't been in an earthquake. Would be pretty scary I'm sure, not ever having been in one. They can be so destructive. Just hurts my heart to hear the news after a big one has hit. - Great topic though, and lens. - Have a good one Shea!

    • profile image


      8 years ago

      Oh my good ness YES I have had such an experience and in the most unlikely of places -- er -- on my sofa, one Saturday afternoon ... in Columbus, Ohio!

    • profile image


      8 years ago

      Interesting, but I don't understand your paragraph about the logarithmic scale, perhaps the figures need attention

    • mythphile profile image

      Ellen Brundige 

      9 years ago from California

      Just yesterday, I felt the house give a little shake, accompanied by a "cr-reak!" sound, and thought, "Hey, that felt like about a 4!" So the Richter Scale isn't very exact, but those of us who live in geologically active areas know what they mean about as well as people in other areas can tell "hey, it's 70 degrees!" (F) or "Feels like about 10" (C).

      I would like to suggest two links to you that I use all the time:

      USGS homepage, with recent earthquakes updated continuously around the world...

      "Did You Feel It?" -- help improve earthquake science by filing a report when you experience a quake, or view maps of responses to see how severe quakes felt in different areas --

      I'm adding this lens to my new Squidoo Museum lensography, attempting to showcase good lenses on fascinating, informative topics. :)

    • papawu profile image


      9 years ago

      Well done. I am very familiar with the info within your lens. I grew up in Southern California's San Fernando Valley pretty much right over the San Andreas fault. I lost my house in the big 1994 Northridge earthquake and we just had a 4.6 here in Los Angeles this past Sunday. If it's possible I have become used to them and actually expect them to happen all the time since we probably have a few hundred small after shocks everyday out here. You can't feel them, but we all know they are here.

    • BarbRad profile image

      Barbara Radisavljevic 

      9 years ago from Templeton, CA

      I discovered your page while looking for lenses to link to in the lens I just wrote about my experience in the San Simeon / Paso Robles earthquake in 2003. Even though I've lived in California all my life and considered small earthquakes part of that life, my attitude changed when I first experienced and had to clean up after a 6.5 quake. But for the grace of God I might have been trapped in an upstairs bedroom until someone could dig through all the rubble to get to me. But I had gone downstairs five minutes before the quake happened. I doubt if anyone living through a big one will ever have the same attitude as before again. Thanks for putting all the work into this lens and offering so much information.


    • dc64 lm profile image

      dc64 lm 

      9 years ago

      I've never been through an earthquake and hope to never experience one. I lived in Monterey, California for a year, and felt a few very slight tremors, but that was nothing, really. You pictures tell the story, and I can't imagine what it must have been like for those people.

    • kencasey profile image


      9 years ago

      I like how you presented the Richter scale. More important than just encyclopedic dry facts are the photos and explanation you used to support your story. Thanks for sharing.

    • LisaDH profile image


      10 years ago

      I remember the '89 Loma Prieta quake well. I was driving on the San Mateo bridge when my car started swerving. I thought I'd blown one or more tires until I realized the whole bridge was moving. Great info. 5*

    • profile image


      10 years ago

      Great lens and very interesting.

      I was in Las Vegas when the big one hit California in the 90's and that's as close as I want to ever be. The bed was shaking, the hanging lamps were swinging and when we looked out the windows you could see the tops of the buildings swaying.

      I'm in the Midwest and all experts predict that the New Madrid fault will shake loose in the next few years. I just got earthquake insurance on my house last week. Better prepared now, than sorry later!

      Give me a tornado anyday--at least you can usually see what you're up against before it hits you!

    • ArtSiren LM profile image

      ArtSiren LM 

      10 years ago

      Very interesting lens. I've learned something new! We had an earthquake here in the UK a few months ago - quite surreal as it was in the early hours and I was half asleep, you know, just at the point where my brain was struggling to figure out if it was dream or reality! Spooky!!

    • profile image


      10 years ago

      This is what I've been looking for! I'm totally afraid of earthquakes! I got traumatized when I experienced one in the mid 70's when I was only 8 years old and we got caught in a more or less 7 on the Richter scale! Thanks for this lens! I hope you have other lenses regarding how to survive a shaker detail by detail. By the way, I've heard of this "Triangle..." something. It says it's even more effective in protecting you as compared to hiding under tables. It explains that you just need to lie next to a table, not under it during earthquake to survive. any comment? Sorry, I forget the full name of it..."

      Mark " Flip Flop checks " Serra

    • RuthCoffee profile image

      Ruth Coffee 

      10 years ago from Zionsville, Indiana

      Generally we don't have earthquakes here in the Midwest but...we did have one just a couple of months ago. Great lens!

    • profile image


      10 years ago

      I love reading about weather and natural disasters. Fascinating! Great work here!

    • ElizabethJeanAl profile image


      10 years ago

      I tried to check out your nuclear energy lens but kept getting bumped off. I would click on it, 10 seconds later I would get bumped all the way off Squidoo. I tried several times and its not happening when I'm on any other lens.


    • CrypticFragment1 profile image

      Tammy Winand 

      10 years ago from McleodGanj HP India

      great lens! I am an "earthquake watcher"... I track magnitude 5.0 in my My Yahoo! page

      I have only ever been in a very tiny 3.2 but it was in York, PA (Easter 1985)which made it seem pretty freaky!

      best wishes

    • cappuccino136 profile image


      10 years ago

      Very informative and nicely done lens. The pictures look great.

    • ElizabethJeanAl profile image


      10 years ago

      We live on a fault line. We've had a few small earthquakes but we're due for a big one.

      Thanks for the information.



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