Web-Based Program Calculates Effects of an Earth Impact

http://uanews.org/cgi-bin/WebObjects...ArticleID=8820


WEB-BASED PROGRAM CALCULATES EFFECTS OF AN EARTH IMPACT
From Lori Stiles, UA News Services, 520-621-1877
April 7,2004

------------------------------
Contact Information

H. Jay Melosh
520-621-2806


Robert Marcus


Gareth Collins
520-626-5065


Related Web site
Earth Impact Effects Program
http://www.lpl.arizona.edu/impacteffects

------------------------------------------


Next time an asteroid or comet is on a collision course with Earth you can
go to a web site to find out if you have time to finish lunch or need to
jump in the car and DRIVE.

University of Arizona scientists are launching an easy-to-use, web-based
program that tells you how the collision will affect your spot on the globe
by calculating several environmental consequences of its impact.

Starting today, the program is online at
http://www.lpl.arizona.edu/impacteffects

You type in your distance from the predicted impact site, the size and type
of projectile (e.g. ice, rock, or iron) and other information. Then the
Earth Impact Effects Program calculates impact energies and crater size. It
next summarizes thermal radiation, seismic shaking, ejecta deposition (where
all that flying stuff will land), and air-blast effects in language that
non-scientists understand.

For those who want to know how all these calculations are made, the web page
will include "a description of our algorithm, with citations to the
scientific sources used," said Robert Marcus, a UA undergraduate in the
UA/NASA Space Grant Program. He discussed the project recently at the 35th
Lunar and Planetary Science Conference meeting in Houston, Texas.

Marcus developed the web site in collaboration with planetary sciences
Regents¹ Professor H. Jay Melosh and research associate Gareth Collins of
UA¹s Lunar and Planetary Laboratory.

Melosh is a leading expert on impact cratering and one of the first
scientists reporters call when rumors of big, Earth-smashing objects begin
to circulate.

Reporters and scientists both want to know the same thing: how much damage a
particular collision would wrack on communities near the impact site.

The web site is valuable for scientists because they don't have to spend
time digging up the equations and data needed to calculate the effects,
Melosh said. Similarly, it makes the information available to reporters and
other non-scientists who don't know how to make the calculations.

"It seemed to us that this is something we could automate, if we could find
some very capable person to help us construct the website," Melosh said.

That person turned out to be Marcus, who is majoring in computer engineering
and physics. He applied to work on the project as a paid intern through the
UA/NASA Space Grant Program.

Marcus built the web-based program around four environmental effects. In
order of their occurrence, they a

1) Thermal radiation. An expanding fireball of searing vapor occurs at
impact. The program calculates how this fireball will expand, when maximum
radiation will occur, and how much of the fireball will be seen above the
horizon.

The researchers based their radiation calculations on information found in
"The Effect of Nuclear Weapons." This 1977 book, by the U.S. Defense
Department and U.S. Department of Energy, details "considerable research
into what different degrees of thermal radiation from blasts will do,"
Melosh noted.

"We determine at a given distance what type of damage the radiation causes,"
Marcus said. "We have descriptions like when grass will ignite, when plywood
or newspaper will ignite, when humans will suffer 2nd or 3rd degree burns."

2) Seismic shaking. The impact generates seismic waves that travel far from
the impact site. The program uses California earthquake data and computes a
Richter scale magnitude for the impact. Accompanying text describes shaking
intensity at the specified distance from the impact site using a modified
Mercalli scale This is a set of 12 descriptions ranging from "general
destruction" to "only mildly felt."

Now suppose the dinosaurs had this program 65 million years ago. They could
have used it to determine the environmental consequences of the
15-kilometer-diameter asteroid that smashed into Earth, forming the
Chicxulub Crater.

The program would have told them to expect seismic shaking of magnitude 10.2
on the Richter scale. They also would have found (supposing that the
continents were lined up as they are now) that the ground would be shaking
so violently 1,000 kilometers (600 miles) away in Houston that dinosaurs
living there would have trouble walking, or even standing up.

If the Chicxulub Crater-impact occurred today, glass in Houston would break.
Masonry and plaster would crack. Trees and bushes would shake, ponds would
form waves and become turbid with mud, sand and gravel banks would cave in,
and bells in Houston schools and churches would ring from ground shaking.

3) Ejecta deposition. The team used a complicated ballistics travel-time
equation to calculate when and where debris blown out of the impact crater
would rain back down on Earth. Then they used data gathered from
experimental explosions and measurements of craters on the moon to calculate
how deep the ejecta blanket would be at and beyond the impact-crater rim.

They also determined how big the ejecta particles would be at different
distances from impact, based on observations that Melosh and UA¹s Christian
J. Schaller published earlier when they analyzed ejecta on Venus.

OK, back to the dinosaurs. Houston would have been covered by an
80.8-centimeter- (32-inch-) thick blanket of debris, with particles
averaging 2.8 mm (about 1/8th inch) in size. They would have arrived 8
minutes and 15 seconds after impact (meaning they got there at more than
4,000 mph).

4) Air blast. Impacts also produce a shock wave in the atmosphere that, by
definition, moves faster than the speed of sound. The shock wave creates
intense air pressure and severe winds, but decays to the speed of sound
while it¹s still close to the fireball, Melosh noted. "We translate that
decreasing pressure in terms of decibels from ear-and-lung-rupturing
sound, to being as loud as heavy traffic, to being only as loud as a
whisper."

The program calculates maximum pressures and wind velocities based on test
results from pre-1960s nuclear blasts. Researchers at those blasts erected
brick structures at the Nevada Test Site to study blast wave effects on
buildings. The UA team used that information to describe damage in terms of
buildings and bridges collapsing, cars bowled over by wind, or forests being
blown down.

Dinosaurs living in Houston would have heard the Chicxulub impact as loud as
heavy traffic and basked in 30 mph winds.

Too cool. I sure wish they'd add ocean depths, distance from
shores and resulting tsunami wave heights to the program.

Rick

Starting today, the program is online at
http://www.lpl.arizona.edu/impacteffects

You type in your distance from the predicted impact site, the size and type
of projectile (e.g. ice, rock, or iron) and other information. Then the
Earth Impact Effects Program calculates impact energies and crater size. It
next summarizes thermal radiation, seismic shaking, ejecta deposition (where
all that flying stuff will land), and air-blast effects in language that
non-scientists understand.

For those who want to know how all these calculations are made, the web page
will include "a description of our algorithm, with citations to the
scientific sources used," said Robert Marcus, a UA undergraduate in the
UA/NASA Space Grant Program. He discussed the project recently at the 35th
Lunar and Planetary Science Conference meeting in Houston, Texas.

Marcus developed the web site in collaboration with planetary sciences
Regents¹ Professor H. Jay Melosh and research associate Gareth Collins of
UA¹s Lunar and Planetary Laboratory.

Melosh is a leading expert on impact cratering and one of the first
scientists reporters call when rumors of big, Earth-smashing objects begin
to circulate.

Reporters and scientists both want to know the same thing: how much damage a
particular collision would wrack on communities near the impact site.

The web site is valuable for scientists because they don't have to spend
time digging up the equations and data needed to calculate the effects,
Melosh said. Similarly, it makes the information available to reporters and
other non-scientists who don't know how to make the calculations.

"It seemed to us that this is something we could automate, if we could find
some very capable person to help us construct the website," Melosh said.

That person turned out to be Marcus, who is majoring in computer engineering
and physics. He applied to work on the project as a paid intern through the
UA/NASA Space Grant Program.

Marcus built the web-based program around four environmental effects. In
order of their occurrence, they a

1) Thermal radiation. An expanding fireball of searing vapor occurs at
impact. The program calculates how this fireball will expand, when maximum
radiation will occur, and how much of the fireball will be seen above the
horizon.

The researchers based their radiation calculations on information found in
"The Effect of Nuclear Weapons." This 1977 book, by the U.S. Defense
Department and U.S. Department of Energy, details "considerable research
into what different degrees of thermal radiation from blasts will do,"
Melosh noted.

"We determine at a given distance what type of damage the radiation causes,"
Marcus said. "We have descriptions like when grass will ignite, when plywood
or newspaper will ignite, when humans will suffer 2nd or 3rd degree burns."

2) Seismic shaking. The impact generates seismic waves that travel far from
the impact site. The program uses California earthquake data and computes a
Richter scale magnitude for the impact. Accompanying text describes shaking
intensity at the specified distance from the impact site using a modified
Mercalli scale This is a set of 12 descriptions ranging from "general
destruction" to "only mildly felt."

Now suppose the dinosaurs had this program 65 million years ago. They could
have used it to determine the environmental consequences of the
15-kilometer-diameter asteroid that smashed into Earth, forming the
Chicxulub Crater.

The program would have told them to expect seismic shaking of magnitude 10.2
on the Richter scale. They also would have found (supposing that the
continents were lined up as they are now) that the ground would be shaking
so violently 1,000 kilometers (600 miles) away in Houston that dinosaurs
living there would have trouble walking, or even standing up.

If the Chicxulub Crater-impact occurred today, glass in Houston would break.
Masonry and plaster would crack. Trees and bushes would shake, ponds would
form waves and become turbid with mud, sand and gravel banks would cave in,
and bells in Houston schools and churches would ring from ground shaking.

3) Ejecta deposition. The team used a complicated ballistics travel-time
equation to calculate when and where debris blown out of the impact crater
would rain back down on Earth. Then they used data gathered from
experimental explosions and measurements of craters on the moon to calculate
how deep the ejecta blanket would be at and beyond the impact-crater rim.

They also determined how big the ejecta particles would be at different
distances from impact, based on observations that Melosh and UA¹s Christian
J. Schaller published earlier when they analyzed ejecta on Venus.

OK, back to the dinosaurs. Houston would have been covered by an
80.8-centimeter- (32-inch-) thick blanket of debris, with particles
averaging 2.8 mm (about 1/8th inch) in size. They would have arrived 8
minutes and 15 seconds after impact (meaning they got there at more than
4,000 mph).

4) Air blast. Impacts also produce a shock wave in the atmosphere that, by
definition, moves faster than the speed of sound. The shock wave creates
intense air pressure and severe winds, but decays to the speed of sound
while it¹s still close to the fireball, Melosh noted. "We translate that
decreasing pressure in terms of decibels from ear-and-lung-rupturing
sound, to being as loud as heavy traffic, to being only as loud as a
whisper."

The program calculates maximum pressures and wind velocities based on test
results from pre-1960s nuclear blasts. Researchers at those blasts erected
brick structures at the Nevada Test Site to study blast wave effects on
buildings. The UA team used that information to describe damage in terms of
buildings and bridges collapsing, cars bowled over by wind, or forests being
blown down.

Dinosaurs living in Houston would have heard the Chicxulub impact as loud as
heavy traffic and basked in 30 mph winds.

Rick wrote:
Too cool. I sure wish they'd add ocean depths, distance from
shores and resulting tsunami wave heights to the program.

Rick


Starting today, the program is online at
http://www.lpl.arizona.edu/impacteffects

You type in your distance from the predicted impact site, the size and type
of projectile (e.g. ice, rock, or iron) and other information. Then the
Earth Impact Effects Program calculates impact energies and crater size. It
next summarizes thermal radiation, seismic shaking, ejecta deposition (where
all that flying stuff will land), and air-blast effects in language that
non-scientists understand.

For those who want to know how all these calculations are made, the web page
will include "a description of our algorithm, with citations to the
scientific sources used," said Robert Marcus, a UA undergraduate in the
UA/NASA Space Grant Program. He discussed the project recently at the 35th
Lunar and Planetary Science Conference meeting in Houston, Texas.

Marcus developed the web site in collaboration with planetary sciences
Regents¹ Professor H. Jay Melosh and research associate Gareth Collins of
UA¹s Lunar and Planetary Laboratory.

Melosh is a leading expert on impact cratering and one of the first
scientists reporters call when rumors of big, Earth-smashing objects begin
to circulate.

Reporters and scientists both want to know the same thing: how much damage a
particular collision would wrack on communities near the impact site.

The web site is valuable for scientists because they don't have to spend
time digging up the equations and data needed to calculate the effects,
Melosh said. Similarly, it makes the information available to reporters and
other non-scientists who don't know how to make the calculations.

"It seemed to us that this is something we could automate, if we could find
some very capable person to help us construct the website," Melosh said.

That person turned out to be Marcus, who is majoring in computer engineering
and physics. He applied to work on the project as a paid intern through the
UA/NASA Space Grant Program.

Marcus built the web-based program around four environmental effects. In
order of their occurrence, they a

1) Thermal radiation. An expanding fireball of searing vapor occurs at
impact. The program calculates how this fireball will expand, when maximum
radiation will occur, and how much of the fireball will be seen above the
horizon.

The researchers based their radiation calculations on information found in
"The Effect of Nuclear Weapons." This 1977 book, by the U.S. Defense
Department and U.S. Department of Energy, details "considerable research
into what different degrees of thermal radiation from blasts will do,"
Melosh noted.

"We determine at a given distance what type of damage the radiation causes,"
Marcus said. "We have descriptions like when grass will ignite, when plywood
or newspaper will ignite, when humans will suffer 2nd or 3rd degree burns."

2) Seismic shaking. The impact generates seismic waves that travel far from
the impact site. The program uses California earthquake data and computes a
Richter scale magnitude for the impact. Accompanying text describes shaking
intensity at the specified distance from the impact site using a modified
Mercalli scale This is a set of 12 descriptions ranging from "general
destruction" to "only mildly felt."

Now suppose the dinosaurs had this program 65 million years ago. They could
have used it to determine the environmental consequences of the
15-kilometer-diameter asteroid that smashed into Earth, forming the
Chicxulub Crater.

The program would have told them to expect seismic shaking of magnitude 10.2
on the Richter scale. They also would have found (supposing that the
continents were lined up as they are now) that the ground would be shaking
so violently 1,000 kilometers (600 miles) away in Houston that dinosaurs
living there would have trouble walking, or even standing up.

If the Chicxulub Crater-impact occurred today, glass in Houston would break.
Masonry and plaster would crack. Trees and bushes would shake, ponds would
form waves and become turbid with mud, sand and gravel banks would cave in,
and bells in Houston schools and churches would ring from ground shaking.

3) Ejecta deposition. The team used a complicated ballistics travel-time
equation to calculate when and where debris blown out of the impact crater
would rain back down on Earth. Then they used data gathered from
experimental explosions and measurements of craters on the moon to calculate
how deep the ejecta blanket would be at and beyond the impact-crater rim.

They also determined how big the ejecta particles would be at different
distances from impact, based on observations that Melosh and UA¹s Christian
J. Schaller published earlier when they analyzed ejecta on Venus.

OK, back to the dinosaurs. Houston would have been covered by an
80.8-centimeter- (32-inch-) thick blanket of debris, with particles
averaging 2.8 mm (about 1/8th inch) in size. They would have arrived 8
minutes and 15 seconds after impact (meaning they got there at more than
4,000 mph).

4) Air blast. Impacts also produce a shock wave in the atmosphere that, by
definition, moves faster than the speed of sound. The shock wave creates
intense air pressure and severe winds, but decays to the speed of sound
while it¹s still close to the fireball, Melosh noted. "We translate that
decreasing pressure in terms of decibels from ear-and-lung-rupturing
sound, to being as loud as heavy traffic, to being only as loud as a
whisper."

The program calculates maximum pressures and wind velocities based on test
results from pre-1960s nuclear blasts. Researchers at those blasts erected
brick structures at the Nevada Test Site to study blast wave effects on
buildings. The UA team used that information to describe damage in terms of
buildings and bridges collapsing, cars bowled over by wind, or forests being
blown down.

Dinosaurs living in Houston would have heard the Chicxulub impact as loud as
heavy traffic and basked in 30 mph winds.



Considering the Richter scale is logarithmic, how can you have a 10.2
magnitude quake??

There's likely an upper limit on the size of the impacting object.
I tried crashing Mars into the Earth (4000 mile diameter ball of
rock, at 17 miles/sec (threw in extra as Earth's gravity would
speed it up a bunch) at a 45 degree angle. The program predicts
an earthquake 15.7 on the Richter Scale. "Conspicuous cracks in ground. "

I'm likely outside the valid range of this program.

Logrythums have no upper limit.
The Alaska Good Friday earthquake in 1964 was around 9.4. One house
moved 1/4 mile. A tsunami went up a river mouth that closed very slowly
and ended 1,000 feet above sea level.

Jo Schaper wrote:
=

Rick wrote:
Too cool. I sure wish they'd add ocean depths, distance from
shores and resulting tsunami wave heights to the program.

Rick


Starting today, the program is online at
http://www.lpl.arizona.edu/impacteffects

You type in your distance from the predicted impact site, the size an=
d type
of projectile (e.g. ice, rock, or iron) and other information. Then t=
he
Earth Impact Effects Program calculates impact energies and crater si=
ze. It
next summarizes thermal radiation, seismic shaking, ejecta deposition=
(where
all that flying stuff will land), and air-blast effects in language t=
hat
non-scientists understand.

For those who want to know how all these calculations are made, the w=
eb page
will include "a description of our algorithm, with citations to the
scientific sources used," said Robert Marcus, a UA undergraduate in t=
he
UA/NASA Space Grant Program. He discussed the project recently at the=
35th
Lunar and Planetary Science Conference meeting in Houston, Texas.

Marcus developed the web site in collaboration with planetary science=
s
Regents=B9 Professor H. Jay Melosh and research associate Gareth Coll=
ins of
UA=B9s Lunar and Planetary Laboratory.

Melosh is a leading expert on impact cratering and one of the first
scientists reporters call when rumors of big, Earth-smashing objects =
begin
to circulate.

Reporters and scientists both want to know the same thing: how much d=
amage a
particular collision would wrack on communities near the impact site.=


The web site is valuable for scientists because they don't have to sp=
end
time digging up the equations and data needed to calculate the effect=
s,
Melosh said. Similarly, it makes the information available to reporte=
rs and
other non-scientists who don't know how to make the calculations.

"It seemed to us that this is something we could automate, if we coul=
d find
some very capable person to help us construct the website," Melosh sa=
id.

That person turned out to be Marcus, who is majoring in computer engi=
neering
and physics. He applied to work on the project as a paid intern throu=
gh the
UA/NASA Space Grant Program.

Marcus built the web-based program around four environmental effects.=
In
order of their occurrence, they a

1) Thermal radiation. An expanding fireball of searing vapor occurs a=
t
impact. The program calculates how this fireball will expand, when ma=
ximum
radiation will occur, and how much of the fireball will be seen above=
the
horizon.

The researchers based their radiation calculations on information fou=
nd in
"The Effect of Nuclear Weapons." This 1977 book, by the U.S. Defense
Department and U.S. Department of Energy, details "considerable resea=
rch
into what different degrees of thermal radiation from blasts will do,=
"
Melosh noted.

"We determine at a given distance what type of damage the radiation c=
auses,"
Marcus said. "We have descriptions like when grass will ignite, when =
plywood
or newspaper will ignite, when humans will suffer 2nd or 3rd degree b=
urns."

2) Seismic shaking. The impact generates seismic waves that travel fa=
r from
the impact site. The program uses California earthquake data and comp=
utes a
Richter scale magnitude for the impact. Accompanying text describes s=
haking
intensity at the specified distance from the impact site using a modi=
fied
Mercalli scale This is a set of 12 descriptions ranging from "general=

destruction" to "only mildly felt."

Now suppose the dinosaurs had this program 65 million years ago. They=
could
have used it to determine the environmental consequences of the
15-kilometer-diameter asteroid that smashed into Earth, forming the
Chicxulub Crater.

The program would have told them to expect seismic shaking of magnitu=
de 10.2
on the Richter scale. They also would have found (supposing that the
continents were lined up as they are now) that the ground would be sh=
aking
so violently 1,000 kilometers (600 miles) away in Houston that dinosa=
urs
living there would have trouble walking, or even standing up.

If the Chicxulub Crater-impact occurred today, glass in Houston would=
break.
Masonry and plaster would crack. Trees and bushes would shake, ponds =
would
form waves and become turbid with mud, sand and gravel banks would ca=
ve in,
and bells in Houston schools and churches would ring from ground shak=
ing.

3) Ejecta deposition. The team used a complicated ballistics travel-t=
ime
equation to calculate when and where debris blown out of the impact c=
rater
would rain back down on Earth. Then they used data gathered from
experimental explosions and measurements of craters on the moon to ca=
lculate
how deep the ejecta blanket would be at and beyond the impact-crater =
rim.

They also determined how big the ejecta particles would be at differe=
nt
distances from impact, based on observations that Melosh and UA=B9s C=
hristian
J. Schaller published earlier when they analyzed ejecta on Venus.

OK, back to the dinosaurs. Houston would have been covered by an
80.8-centimeter- (32-inch-) thick blanket of debris, with particles
averaging 2.8 mm (about 1/8th inch) in size. They would have arrived =
8
minutes and 15 seconds after impact (meaning they got there at more t=
han
4,000 mph).

4) Air blast. Impacts also produce a shock wave in the atmosphere tha=
t, by
definition, moves faster than the speed of sound. The shock wave crea=
tes
intense air pressure and severe winds, but decays to the speed of sou=
nd
while it=B9s still close to the fireball, Melosh noted. "We translate=
that
decreasing pressure in terms of decibels from ear-and-lung-rupturing=

sound, to being as loud as heavy traffic, to being only as loud as a
whisper."

The program calculates maximum pressures and wind velocities based on=
test
results from pre-1960s nuclear blasts. Researchers at those blasts er=
ected
brick structures at the Nevada Test Site to study blast wave effects =
on
buildings. The UA team used that information to describe damage in te=
rms of
buildings and bridges collapsing, cars bowled over by wind, or forest=
s being
blown down.

Dinosaurs living in Houston would have heard the Chicxulub impact as =
loud as
heavy traffic and basked in 30 mph winds.



Considering the Richter scale is logarithmic, how can you have a 10.2
magnitude quake??

Mike Schwab wrote:

Logrythums have no upper limit.
The Alaska Good Friday earthquake in 1964 was around 9.4. One house
moved 1/4 mile. A tsunami went up a river mouth that closed very slowly
and ended 1,000 feet above sea level.


You are partially correct, though not about the Good Friday EQ. Not
according to my figures. 9.2 Mercalli, 8.4 Richter. Also, I know enough
to be dangerous--i.e., magnitude figures are often revised downward as
more stations report in. Apparently, there actually was a reliable 9.0
MR in the Chilean Andes in 1960.

The basis of my question is: since 10.0 is theoretically the point at
which you have total structural failure of the planet, does it really
make any sense beyond that except to say "really, really BIG?"


From 1980 interview with Chas. F Richter on
http://neic.usgs.gov/neis/seismology..._richter.html:

"I'm glad to see the press now referring to the "open-ended" Richter
scale. Magnitude numbers simply represent measurement from a seismograph
record - logarithmic to be sure but with no implied ceiling. The highest
magnitudes assigned so far to actual earthquakes are about 9, but that
is a limitation in the Earth, not in the scale."



Considering the Richter scale is logarithmic, how can you have a 10.2
magnitude quake??

"JS" == Jo Schaper writes:

JS Mike Schwab wrote:

Considering the Richter scale is logarithmic, how can you have a
10.2 magnitude quake??

Logrythums have no upper limit. [...]

[...]
JS The basis of my question is: since 10.0 is theoretically the point
JS at which you have total structural failure of the planet, does it
JS really make any sense beyond that except to say "really, really
JS BIG?"

What leads you to the belief that a magnitude 10 earthquake implies
"total structural failure of the planet"? Indeed, the quote you have
below from Richter himself states that ther is "no implied ceiling" to
the Richter scale.

JS From 1980 interview with Chas. F Richter on
JS http://neic.usgs.gov/neis/seismology..._richter.html:

JS "I'm glad to see the press now referring to the "open-ended"
JS Richter scale. Magnitude numbers simply represent measurement from
JS a seismograph record - logarithmic to be sure but with no implied
JS ceiling. The highest magnitudes assigned so far to actual
JS earthquakes are about 9, but that is a limitation in the Earth,
JS not in the scale."

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

Jo Schaper wrote:


The basis of my question is: since 10.0 is theoretically the point at
which you have total structural failure of the planet, does it really
make any sense beyond that except to say "really, really BIG?"


Jo - I have never read that before. Where does it come from?
Normal eq's are limited by depth of crust and length of shear,
but impact energy into the crust is a different mechanism.

Jim Lillie - Electrical engineer interested in geology.

Mike Schwab wrote:
[snip]

The basis of my question is: since 10.0 is theoretically the point at
which you have total structural failure of the planet, does it really
make any sense beyond that except to say "really, really BIG?"

The Richter scale measures an EQs energy, it is open ended. The
maximum EQ energy is a measure of the shear stress that rocks can
hold before failure and an EQ. I don't remember the exact maximum
but it is something like 9.5 Richter. Of course this depends on the
type and enviroment of the rocks so YMMV in any particular EQ.

I had not heard that 10.0 Richter would mean Total Structural Failure.

A impact with 15.5 Richter would have one million times ( 10^6 )
more energy than the normal failure level of rocks. What happens
to this excess energy? My guess is that it goes into thermal
( the fireball ) and kinetic ( large chunks of rocks moving real
fast ) modes.

tom

--
We have discovered a therapy ( NOT a cure )
for the common cold. Play tuba for an hour.

"Tom Kirke" wrote in message ...
Mike Schwab wrote:
[snip]

The basis of my question is: since 10.0 is theoretically the point at
which you have total structural failure of the planet, does it really
make any sense beyond that except to say "really, really BIG?"

The Richter scale measures an EQs energy, it is open ended. The
maximum EQ energy is a measure of the shear stress that rocks can
hold before failure and an EQ. I don't remember the exact maximum
but it is something like 9.5 Richter. Of course this depends on the
type and enviroment of the rocks so YMMV in any particular EQ.

I had not heard that 10.0 Richter would mean Total Structural Failure.

A impact with 15.5 Richter would have one million times ( 10^6 )
more energy than the normal failure level of rocks. What happens
to this excess energy? My guess is that it goes into thermal
( the fireball ) and kinetic ( large chunks of rocks moving real
fast ) modes.

Someone (maybe it was in this group) claimed a 2-mile wide
asteroid impact would create a mile-high tsunami, and throw
a chunk of sea floor into orbit around the Earth.

No idea if that's true or not, but it sure sounded impressive.
Hard to comprehend the energies involved with these impacts.

Rick