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  • Earthquakes strike all over the world, and once they're over a certain threshold, they

  • become BIG news.

  • But what do those numbers they tell you on the news really mean?

  • Nepal was recently hit by a 7.3 on the Richter Scale, less than 3 weeks after being hit by

  • a 7.8.

  • The 7.8 destroyed buildings, killed thousands and caused an avalanche; the 7.3 caused a

  • panic, and killed only a few dozen.

  • Does Zero Point Five on the scale make that big a difference?

  • Firstly, let me step back for a bit, when you describe a great dessert to a friend,

  • you probably give it a rating.

  • We humans love to rate things -- but to truly rate it fairly, you'd have to understand the

  • ingredients, the preparation, the plating, and the ideal dessert comparison, what you've

  • just eaten prior, what you're drinking, where you're sitting, the temperature in the room

  • you're in and your mood at the time; not to mention whether you had a fight with your

  • friend earlier that day!!

  • Science needs history, context, and tons of points of data, and that's just for a piece

  • of cake!

  • How can you take all that data and turn it into one simple rating?

  • Most people don't.

  • They measure how they FEEL about it, right?

  • Like a layer cake, earthquakes are all different.

  • When rocks slide, knock and buffet against one another; they can slip, crack or jerk

  • and cause an earthquake, but the friction, the fault, the pressure, depth, type of rock

  • and varied stressors of its history; all matter.

  • To turn that into one number is pretty crazy, if you think about it.

  • The Richter scale was invented in the 1930s to give some understanding to the magnitude

  • of a quake as measured by seismographs; ground monitoring equipment.

  • It's logarithmic, so every 1.0 point on the scale is a TEN FOLD increase.

  • So a 3 to a 4 is a ten-fold increase, and 3 to a 5 is 100 fold; or, put another way,

  • a 7 is a 10,000 times more powerful than a 3.

  • The U.S. Geological Survey says there are 1.4 million quakes that register above 2.0

  • every year, and only 16 that get a 7 or higher, but even after I've explained it to you, do

  • you know what it means?

  • I don't!

  • Richter is only concerned with the amount of energy released by a single quake, and

  • doesn't tell us much about what it DID.

  • Maybe it was deep, or away from a populated area, maybe the quake was under soft ground,

  • or in the middle of firm bedrock -- all of that would change how it was experienced;

  • or how humans FEEL it.

  • Mercalli Scale or Modified Mercalli Scale, measures intensity.

  • This is used by the U.S. Geological survey to understand how the earthquake FELT on the

  • surface!

  • The Mercalli scale was developed in the 30s too and it uses Roman numerals to determine

  • how intense a quake is from I to XII.

  • It is subjective, so, for example, a II is weak and is quote "Felt only by a few persons

  • at rest,especially on upper floors of buildings," but a VI is strong and quote "Felt by all,

  • many are frightened.

  • Some heavy furniture is moved; a few instances of fallen plaster.

  • Damage slight."

  • This measure of how it FEELS adds more data to what happened in an earthquake, moving

  • us closer to understanding what really happened!

  • There's also the Moment Magnitude scale, which is a new measure for quakes.

  • Moment Magnitude allows scientists to use computer models to create synthetic seismograms

  • and determine exactly how the energy released relates to the magnitude of a quake.

  • Essentially how far a fault moved, and the force required to move it.

  • It gets seismologists really excited because it's WAY more accurate than the antiquated

  • Richter measurements, works all over the world as a standard measure, and can go above M8,

  • which Richter cannot.

  • Okay, so now that you know the basics

  • According to the Incorporated Research Institutions for Seismology, the April 25th earthquake

  • in Nepal was a M7.8 with MMI ranging from IV to IX.

  • Most of the reports were in V to VI -- so it felt strong, the ground moved and for some

  • people it was severe and violent,.

  • This complicated cocktail of factors that have to be considered help determine how earthquakes

  • are experienced, and categorized; just like anything we can always learn more.

Earthquakes strike all over the world, and once they're over a certain threshold, they


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How Does The Richter Scale Work?

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    joey joey に公開 2021 年 04 月 26 日