The Richter Scale without all that pesky math stuff

With all the earthquakes we have been experiencing lately people are trying to get a sense of just what the difference is between a magnitude 5.5 and a magnitude 6.0. Like many things in science it’s not exactly a simple thing to answer. I decided to hit the web and look around on sites. I hit the USGS, Ask.com, Google, as well as several university sites that do seismic work.

To put it as simply as I can we will start with what an earthquake is. When the plates that make up the upper levels of our planet push together they bind up and create unbelievable pressure. Eventually those two seemingly unmovable forces build up enough pressure that one of them snaps and a massive section of rock plows past the other. To get the idea of what that snap means, imagine a firework blowing up right next to you. That booming concussion that you would feel is exactly what happens deep below the earth’s surface.

The concussion from the snap is energy, and as it moves through the earth from rock to rock it creates a moving wave of vibrating energy.

Now, how does that rolling wave of energy get measured? A seismograph records the vibrations onto a rotating drum and that etching is looked at and points on the wave are measured to provide a measurement of the energy expended by the quake. The Scripps Institute has a cool interactive demonstration that allows you to get a quick feel for how the numbers come together at different points to give you a final number.

We have all the basics out of the way, here is the deal with understanding what magnitude really means. I hate math so this next part is a little tough to get my head around. When looking at magnitude the only way to put the measurement into a manageable format is to use something called a logarithmic scale. The reason being, the amount of energy increases so fast as it travels through the earth the numbers would be too huge to really understand.

The Richter scale grows by powers of 10. An increase of 1 point means the strength of a quake is 10 times greater than the level before it. Here’s how it works: An earthquake registering 2.0 on the Richter scale is 10 times stronger than a quake registering 1.0. A quake registering 3.0 is 10 X 10 or 100 times stronger than a quake registering 1.0 A 4.0 is 10 X 10 X 10 or 1,000 times greater than 1.0 and so on.

Get it— An increase of 1 point means the strength of a quake is 10 times greater than the level before it . That line is key to understanding it.

Finally, if you managed to read all the way to the bottom, here are a couple of Final Jeopardy answers for you.

• The largest earthquake ever measured was in Chile. May 22, 1960 the quake struck measuring 9.5.
• It’s estimated that the meteor that hit the Gulf of Mexico and may have ended the reign of dinosaurs on the planet was a 13 on the Richter scale.
• The Richer scale is a measure of amplitude not damage. Not every 6.0 quake does the same kind of damage. The depth of the quake as well as the kind of bedrock and soils all combine to lessen or intensify the damage.
• The impacts of the planes as well as the final collapse of both World Trade Centers were recorded on a seismograph located 21 miles north of New York City.

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2 Responses to “The Richter Scale without all that pesky math stuff”

1. Phil Says:

There is a lot more below:

Isn’t learning fun?

If anyone is interested, they can sign-up and receive the worldwide earthquake reports by e-mail and if they have a web or blog page they can subscribe to the RSS feeds, mine shows the quakes for the last 14 hours, but I can go back further. Note that the updates and e-mails run a bit later than national news.

The other day I received 5 or 6 e-mails about different quakes or aftershocks just in Chile.

The RSS feed show a portion of a world map and where the quake hit as follows, times are usually in UTC and EST.

“M 2.6, Southern Alaska – 1 hour ago
Monday, March 15, 2010 18:35:18 UTC Monday, March 15, 2010 10:35:18 AM at epicenter Depth: 138.30…”

For e-mails and RSS feeds sign-up here:
http://earthquake.usgs.gov/earthquakes/

Global Seismographic Network (GSN), (there is a legend for the colors).
http://earthquake.usgs.gov/monitoring/gsn/

A nice map (click to enlarge) of the world fault lines, note the one running down the St. Lawrence Seaway, through southern Lake Erie and into New Madrid, Mo. and Memphis,Tennessee area.

Global tectonic activity map of the Earth (GTA)
http://www.gisdevelopment.net/technology/carto/images/image002.gif

Here is a 3 page intro leading up to the map above:
A digital tectonic activity map of the earth (map #-2 on that page)
http://www.gisdevelopment.net/technology/carto/techca0006.htm

New Madrid is also known as: “New Madris Seismic Zone Epicenter Map” and you can find info there on the 1811-1812 quake that cause the Mississippi River to flow backward.
http://www.dnr.mo.gov/geology/geosrv/geores/techbulletin1.htm

And more here:
Mississippi River ran backward ???
http://www.showme.net/~fkeller/quake/mississippi_river_ran_backward.htm

2. Phil Says:

Bruce, I read you have the largets quake posted, but here are the details.

World’s Largest Recorded Earthquake
9.5 Magnitude – May 22, 1960 near Valdivia, Chile
http://geology.com/records/largest-earthquake

South American Cities Moved by Chile’s 8.8 Earthquake
Parts of South America moved up to ten feet westward during the earthquake.
Republished from a March, 2010 press release by Ohio State University.
http://geology.com/press-release/south-american-plate-moves/