Lee, List,
Thanks for the correction to the Mercalli Scale.
And, the LPL impact calculator made no mention
of Raquel! I knew there was something wrong with
that program.
The authors of that program do say that it
performs best on "middling" events and will fail
to give an accurate representation when "extreme"
input parameters are used, and this was pretty
"extreme."
I doubted some of the mildness of the damage
estimates when the antipodal point would still suffer
663 mph winds. I don't think ANY human structures
would stand up to that. Or humans either, when struck
by debris moving at that velocity.
Also, because of the convergence of seismic waves
AT the antipodes, that region would probably actually
be in worse shape than somewhere in-between. The
shock at the antipodal point might be almost as severe
as the impact point! (Chaotic terrain on Mercury
antipodal to Caloris Basin.)
One of the things that makes it so devastating
is the 47 km/sec impact velocity. I reached that figure
by calculating (roughly) the eccentricity of an object
deflected by Saturn or Jupiter into the inner system,
then sorted the short list of known orbits for (small)
objects with that eccentricity of orbit. They all
smacked the Earth at 45 to 50 km/sec.
An impact at 20 to 25 km/sec would only be
1/4th as energetic (still bad, tho). It's the eccentricity
of a deflected Centaur that is their very worst feature.
That, and the absence of Raquel.
Sterling K. Webb
--------------------------------------------
----- Original Message -----
From: "Lee" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Saturday, July 08, 2006 10:14 AM
Subject: Re: [meteorite-list] Japanese impact animation video
----- Original Message -----
From: "Sterling K. Webb" <[EMAIL PROTECTED]>
To: "Francis Graham" <[EMAIL PROTECTED]>;
<[email protected]>
Sent: Saturday, July 08, 2006 4:19 AM
Subject: Re: [meteorite-list] Japanese impact animation video
At the observer's location (20,000 km away), the major seismic shaking
will arrive at approximately 4000 seconds:
Richter Scale Magnitude: 12.8
Mercalli Scale Intensity at a distance of 20000 km: VI. Felt by all, many
frightened, to VII. Damage negligible in buildings of good design and
construction; considerable damage in poorly built or badly designed
structures
Little rocky ejecta reaches this site; fallout is dominated by condensed
rock vapor from the projectile.
The Mercalli Scale estimator has a glitch with this large of Richter
numbers. A 12.8 magnitude quake would give a REAL Mercalli Scale rating
of XII, which is defined as:
"Total damage. Waves seen on ground. Objects thrown up into air"
No man-made structure or natural feature would be recognizable after a
12.8 magnitude quake. Mountains would be ripped apart, river courses
completely disrupted, cities turned into gravel. Picture a cityscape of
playing card structures AFTER the rug is pulled out from under it, and you
get close to the destruction left behind. The earthquake in "One Million
Years B.C." with Raquel Welch comes to mind as a mild interpretation of a
10 magnitude quake.
Lee Cornelius
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