2001-03-03
>From the following website:
http://www.msnbc.com/news/537200.asp
The depth of the quake went from 40 km to 33 miles (53 km). Next report it
will be 40 miles. Where do these numbers come from?
The earthquake was centred 35 miles southwest of Seattle and 33 miles
underground. Scientists said the depth of the quake eased its impact.
John
Keiner ist hoffnungsloser versklavt als derjenige, der irrtümlich glaubt
frei zu sein.
There are none more hopelessly enslaved then those who falsely believe they
are free!
----- Original Message -----
From: "James R. Frysinger" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[EMAIL PROTECTED]>
Sent: Thursday, 2001-03-01 22:58
Subject: [USMA:11404] RE: Seattle quake NOT in SI
Thanks, Dennis! I took this info into my first semester Introductory
Physics lab tonight and incorporated it into my lab briefing.
Jim
On Thu, 01 Mar 2001, Dennis Brownridge wrote:
> We can be happy the USGS gave distances in kilometers, and pronounced it
> correctly, but a much bigger problem is that they give the energy of
quakes
> in those ridiculous "Richter scale" magnitudes, which few
people--geologists
> included--seem to understand. I see on the USGS website that they use at
> least 6 different kinds of "magnitudes," tweaked from Richter's original
> arbitrary scale (1935). It appears that the energy of a quake (in joules)
is
>
> E = (25 000) 10^(1.5 M)
>
> where M is the magnitude, although the constant ranges from about 22 000
to
> 26 000, depending on which "magnitude" they are using and which source you
> are reading. Of course, they don't explain this clearly anywhere. You have
> to convert from all sorts of non-SI garbage--"size," "tons of TNT" [really
> 10^9 thermochemical calories], "dyne-cm," and clumsy logarithms, although
at
> one point they do mention "Newton-meters" [sic]. Considering that these
guys
> are the experts, they do a really terrible job of explaining it, with lots
> of glaring mistakes and ambiguous terminology. Why can't we get scientists
> to read the Standards on measurement?
>
> Anyway, an increase of 1 magnitude represents an increase in quake energy
of
> sqrt(1000), or 31.6 times (i.e., the energy released at the focus or
> hypocenter, the point of slippage deep underground). So, if we use 25 000
> for the constant,
>
> magnitude 2.0 = 25 MJ (the smallest quake you can feel)
> magnitude 3.0 = 800 MJ
> magnitude 4.0 = 25 GJ
> magnitude 5.0 = 800 GJ
> magnitude 6.0 = 25 TJ
> magnitude 7.0 = 800 TJ
> magnitude 8.0 = 25 PJ
> magnitude 9.0 = 800 PJ (about the biggest possible quake)
>
> Two significant digits is apparently the best they can get, given all the
> unknown variables such as the type of rock the quake waves are passing
> through.
>
> Think how quickly the public would come to understand and appreciate SI if
> the government just gave earthquake, food energy, and consumption
statistics
> in joules, as they are supposed to! How interesting that the smallest
quake
> you can feel has the same energy as the food you eat in a couple of days;
> that the Seattle quake released as much energy as the world's population
> uses in 1 minute; and that the largest quakes are bigger than the biggest
> H-bombs! But all that is lost on people because we use so damn many
> different units of energy.
>
> > -----Original Message-----
> > From: James R. Frysinger
> >
> > Our TV crew dodged it. They gave no numbers except for the magnitude,
> > "seven point oh".
--
James R. Frysinger University/College of Charleston
10 Captiva Row Dept. of Physics and Astronomy
Charleston, SC 29407 66 George Street
843.225.0805 Charleston, SC 29424
http://www.cofc.edu/~frysingj [EMAIL PROTECTED]
Cert. Adv. Metrication Specialist 843.953.7644
