No Richter Scale?

Factual Questions
1

Ironic timing with the Haiti earthquake, my wife pointed out to me how my daughter’s science book says the Richter Scale is passe. It is now the “moment magnitude scale (MMS)” which nothing online can clearly explain. Wiki puts the gobblty gook the best saying “Even though the formulae [between Richter and MMS] are different, the new scale retains the familiar continuum of magnitude values defined by the older one.” :rolleyes:

What garbage is this? The new scale is the same as the old scale, but it’s the new scale. Huh? :confused:

2

USGS Earthquake Magnitude Policy

3

However it’s measured, that was a hell of an earthquake. I was in LA for Northridge, at something like 6.7, and a 7 would be quite a lot bigger.

I know they revised the F-scale for tornadoes a few years ago, so I’m not surprised if they’re re-evaluating earthquake scales as well.

4

The point was that Richter was all about calculating the energy released. The public & emergency services care about damage potential.

While those are related ideas, there are ways for high energy quakes to produce little damage-causing motion at the surface and vice versa.

MMS bridges the gap and directly measures damage potential, but uses terminology familiar to the public. So “6.0” still means “damage nearby” and “7.0” still means “devastation nearby”. Even a pretty-boy news anchor can keep that straight.

5

I hope they are changing it to a linear scale that would make sense to people. Why not be able to say clearly one quake is twice as bad as another? Or 3 times worse, clearly? They need such a scale, I hope that is the idea here.

6

It’s not the same…the two scales just roughly line up much of the time. Look at the chart on that Wikipedia page. Two quakes with the same magnitude on one scale don’t necessarily have the same magnitude on the other. The Moment Magnitude scale is designed to give numbers that are roughly comparable to the Richter scale that average folks had gotten used to, but the slight differences account for a more precise and useful method of calculation.

7

That’s unlikely to happen.
People already have no idea about the magnitude of numbers - If you ask how many times bigger a Billion is compared to a Hundred Thousand, you’ll just get blank looks. Now, compare a 9.2 vs a 6.7 earthquake - one is One Billion Five Hundred Eighty-Four Million and the other is Five Million Eleven Thousand. How much more powerful is the bigger Earthquake?

All people need to know is:
>7 = bad
>8 = really bad
>9 = End of the World as We Know it.

8

I’ll agree with beowulff on this one, and add:

You really don’t want a linear scale to cover phenomena dealing with large–sometimes enormous–dynamic ranges. Things like sound intensity (decibels), pitch (octaves), photographic exposure (f-stops) are far more useful and convenient when handled in logarithmic scales. And that’s just for common, everyday things. In technical fields, there are even more applications. Radar cross section, pH, stellar magnitude…the list goes on.

No one wants to deal with numbers where you’re talking about 0.0001 units one second and 100000 units the next. Linear scales can be unwieldy and confusing. It may take a little time to adjust your intuitive senses to a logarithmic scale, but the ease of comparison and calculation (not to mention the compactness of the notation) is well worth it.

9

And, to further drive the point, this is what Richter would look like expressed linearly, starting from Richter 0.0 equals 1.0 on our new scale (provided my math is correct):



Richter Linear
0.0	1.0
0.5	5.6
1.0	31.6
1.5	177.8
2.0	1000.0
2.5	5623
3.0	31,623
3.5	177,828
4.0	1,000,000
4.5	5,623,413
5.0	31,622,777
5.5	177,827,941
6.0	1,000,000,000
6.5	5,623,413,252
7.0	31,622,776,602
7.5	177,827,941,004
8.0	1,000,000,000,000
8.5	5,623,413,251,900
9.0	31,622,776,601,700
9.5	177,827,941,004,000
10

Those with a keen interest probably already know of the Mercalli scale.

http://www.seismo.unr.edu/ftp/pub/louie/class/100/mercalli.html

Note this link is dated 1996.

11

beowulff:

But do you feel fine?