The low pressure center predicted to be over the New Madrid fault on Tuesday morning. Reduction of atmospheric pressure on the ground.
http://tinyurl.com/badtd

The pressure on the fault includes the atmosphere and the overlying rocks. I have my chemistry students do a lab in which they test Boyles law by stacking textbooks on a syringe. To test PxV = k they must know the total pressure on the syringe (which includes the atmosphere) and must therefore find atmospheric pressure in book units. The atmospheric pressure works out to be equivalent to 2.7 textbooks +/-0.4.

Typical air pressure is about 1000 millibars. The central air pressure of hurricane Dennis is 930 millibars according to your link. So there is a 7 % drop in air pressure. Now the chemistry textbook we use has ~ 1000 pages so 2.7 books is 2700 pages. The drop in pressure from hurricane Dennis is equivalent to removing 189 pages from the stack.

Does it really seem likely that removing the atomic structure,periodic table, and bonding units from a single chemistry textbook (actually from a 2.7 book layer of chemistry textbooks spread over the new madrid fault) is enough pressure unloading relative to the much greater pressure from the overlying rocks to cause an earthquake?

Probably a coincidence that there was this earthquke when Dennis the Menace was sorta nearby.

http://earthquake.usgs.gov/recenteqs...prP0518801.htm

It doesn't take much to trigger earthquakes. There were several caused by the Rocky Mountain Aresenal pumping some waste water down some wells near Denver. This low pressure covers a pretty big area compared to a book.

I'm not being flippant, but I really think coincidence is the answer. The depth of that quake was 6km. Even if the entire atmosphere was removed that is a negligible contribution to the total pressure experienced by a fault at a depth of 6 km.

I guess I didn't explain that well enough. Imagine a stack of 3 textbooks covering the entire surface of the Earth. That is approximately equivalent to the atmospheric pressure. I say approximate only because the greater your elevation the less air pressure.

Now stop and think about this. A stack of 3 textbooks is roughly 15 cm thick. Lets assume that the crust down to 6km has a constant density of 2.7 g/cm^3. Lets also assume that the rocks are the same density as the books. (Actually the rocks are greater density than the books in density so the real result will be even worse than suggested by this calculation.

How many books stacks of 3 books do we need to equal 6 km?

The answer is 40,000 stacks? In other words, the pressure on the fault line at a depth of 6km is eqivalent to 120,000 textbooks (actually more considering the assumptions above are too conservative). What we have to visualize is the area of a fault with 120,000 textbook thick layer sitting on it and we remove ~200 pages from the top book over the entire area covered by the books. Those 200 pages are negligible - only .000017% of the total pressure.

But the idea should be easy enough to test with historical data. Is there any evidence in the past of earthquakes being associated with the passage of a hurricane - above normal activity?

As for the example with pumping water - that makes sense because we were messing around with the integrity of rocks much closer to the fault lines. How big were those quakes?

Must Click Watch This Topic For Replies. :wink:

Errrmmm...Kierein's link goes to an earthquake in the British Virgin Islands, that happened on Wednesday night, July 6. I thought the OP was talking about whether Dennis would trigger a quake on the New Madrid fault, as Dennis chugs ashore, today?

Also, there was a previous 2.9 and a 3.0 on July 4 in approximately the same location as the linked EQ (north of Puerto Rico), when Dennis was still just a tropical depression.

Also, according to this storm track map, it doesn't look like Dennis' low-pressure center passed anywhere near Puerto Rico or the BVI. It came in past the coast of Venezuela, so Dennis' low-pressure center wasn't in the right spot to affect the earth's crust in the BVI.

Correlation is not causation.

Eh? Two tons per square foot is a lot more than you get from a stack of 3 textbooks.

Edit: corrected quote.

And...that "minimum central pressure" on the Weather Underground link of 980 mb/28.93 is not for Tuesday--that's the current estimated minimum central pressure, as of 10 p.m. Sunday CDT.

Link.
So, right now, it's estimated to have a minimum central pressure of 980 mb. But by the time the vastly decreased storm system reaches the Midwest on Tuesday, it will presumably no longer have such extreme low pressure.

I get a little more than 1 ton per square ft. 14.7 lbs/ sq. inch x 144 sq. inches per square foot. The books are heavy reading.

Hmmm ... I forgot that the texts cover an area much larger than the diameter of the syringe upon which they are pressing. So the mass of three texts is concentrated onto a syringe of about 3/4 inch diameter.

Tropical Depression Dennis' minimum central pressure, as of 10 a.m. CDT today, was 997 MB or 29.44 inches. And according to the latest weather.com map, as of 11:35 a.m. EDT, this area of low pressure was centered right over the northern Mississippi/Memphis area. And the New Madrid fault zone is the biggest in the Arkansas/Missouri "boot heel", which is where the leading edge of the low pressure system was at 11:35 a.m. EDT.

IOW, if there was gonna be an earthquake, it oughta be right about...NOW...

[glances nervously around dining room to see if china is rattling]
[sees nothing]
[gets on with life]

Ok, I've gone back and checked. I get 1.887 kg per textbook or 4.15 lbs per book.

4.15 lbs x 2.7 textbooks gives a total of 11.2 lbs of textbook.

The diameter of the syringe is 1" so the area of the syringe is .785 square inches (area circle = pi x r^2). (Can't believe I forgot to factor in the small area of the syringe when I came up with that analogy.)

So the total in lbs per square inch for the atmospheric pressure derived from the books is 14.3 lbs per square inch which is consistent with your calculation particularly given the course nature of the lab equipment used.

What changes is my analogy - the atmospheric pressure is equivalent to having the mass of those 2.7 textbooks concentrated over every .785 inches squared, not the area of the textbook itself.

But I think this only underscores the problem further. How many pounds per square inch from the mass of overlying rock at a depth of 6 km? Assuming the 7% drop in area pressure, the total pressure exerted from the atmosphere would change by 1 lb per square inch (using 14.7 as the total). Is that 1lb per square inch not completely overwhelmed by the total pressure of 6km of overlying rock?

besides which, according to the Weather Channel, Ivan hit approximately the same region last year, but was worse. no earthquake then.

heck, doesn't Japan get monsoons occasionally? somebody would've noticed a correlation before.

__________________
Gillian

"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"

"You can't erase icing."

"I can't believe it doesn't work! I found it on the internet, man!"

I tried to take a quick look and see what the EQ history for Puerto Rico and the Virgin Islands was, but didn't come up with a good list on a quick look.

But it would not be unusual to have an earthquake there, I'm sure. So the only way to follow up on the proposed theory is to see if there is any increase in frequency when a hurricane passes over. One lone small earthquake doesn't prove anything.

Just a quick intrusion from one of your local meteorologists....

"Dennis" dropped the pressure at Cape Girardeau, Missouri to only 1006 mb ("Standard Atmosphere" is 1013.2 mb). Many non-tropical storms have generated lower pressure than this, with even more rapid pressure changes. I don't think there's any chance that Dennis will trigger an earthquake. If one occurs, it's merely a coincidence. The area has been rather seismically active lately.

Japan has typhoons, not monsoons. Typhoons are synonymous with hurricanes, but refer to a different geographic area.

__________________
"I am Meteora, supreme goddess of weather" - Meteora, in The Unchained Goddess

One nice thing about being a meteorologist who also likes astronomy is that the sky is always interesting!

I'd visualize it as books stacked 300 high over every block of concrete and every blade of grass. Probably cause an earthquake.

'Course, to further your analogy, you'd have that three hundred book tall layer stacked everywhere and you unload 21 (7%) of them from every stack. Lot of books.

If we stacked them on my car, a 7% decrease would be unloading, let's see, 14.7 * 0.07 * 177.6 * 75.7, divided by 3197, which means it's over 4 times what the car itself weighs. That would tend to rock the shocks.

__________________
http://cleardarksky.com/c/DrhmNCcs0.gif

That's right. A monsoon is a kind of wedding that they have in India.

Meanwhile, the eye of Dennis passed 50 miles east of here yesterday. Strong winds and quite a bit of rain, but no damage, at least here abouts. There was no sign of Mr. Wilson in hot pursuit.

__________________
A person's name, or a mark representing it, as signed personally or by deputy, as in subscribing a letter or other document.

sorry. yes, I knew that . . . .

"he's the local typhoon."

"no, Mother, I think you mean tycoon. a typhoon is a big wind."

"that's what I mean, all right."

--The Thin Man goes Home

__________________
Gillian

"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"

"You can't erase icing."

"I can't believe it doesn't work! I found it on the internet, man!"

I was driving at this time in the St. Louis area and didn't feel it. A little larger than most weekly tremors which are usually below 2.0. I don't think this indicates anything.

http://earthquake.usgs.gov/recenteqsUS/Quakes/nm764.htm

The New Madrid one was 2.8. This one in Alabama was a little smaller at 2.4 but in a little more unusual location.
http://earthquake.usgs.gov/recenteqs.../sejm0712a.htm

Here's the track for those interested. It's still hanging around.

http://www.wunderground.com/tropical.../at200504.html

This one was tiny, mag. 1.6 but I think I felt it in St. Louis. I looked at my watch as the floor had a tiny shock. http://earthquake.usgs.gov/recenteqs...nmhwb0713b.htm

Dennis is still pretty organized.

http://www.wunderground.com/tropical...00504_sat.html

There are often around 10 tropical storms and hurricanes in a typical season.

Now, what are the numbers of earthquakes of the quoted magnitudes in the same period?


Magnitude 2-3 : 300,000

That means roughly around... say... 34 an hour. That doesn't include the below 2.0 (the 1.6 and such...)

I'd say offhand that it would be a decent guess to predict several hundred 2.0-3.0 earthquakes when a hurricane strikes. However, it would not be any better than the prediction of the same when a hurricane is nowhere near. This is another case of correlation taken to mean causation plus not looking at the mean and noise and thereby adding confirmation bias.

We get a lot of mine bursts in Alabama. West Alabama (where my folks hailed from) reminds me of Dunwich. My Mom didn't like to talk about one story she had of a woman with dog-headed babies. I man by the name of Troy Woffard burst while walking down the street in Vernon due to an impaction. Several deformaties. Creepy place.

I think water can lubricate faults. One drill with waste water pumped into the ground out west was said to have triggered some small temblors.

John:

What about the one that happened on July 10 in the same area?

http://earthquake.usgs.gov/recenteqs...nmhwb0710a.htm

Wasn't Dennis still in the Gulf then?

Emphasis mine.

I agree (with the emphasized text). Dennis was centered over Indiana at the time, and the atmospheric pressure over Missouri and northeast Arkansas was not the least bit unusual.

__________________
"I am Meteora, supreme goddess of weather" - Meteora, in The Unchained Goddess

One nice thing about being a meteorologist who also likes astronomy is that the sky is always interesting!

I don't think anything particularly unusual happened even though the center of Dennis was over the New Madrid fault; (unlike Ivan which had landfall at the same spot, but didn't go over the fault area subsequently.) There were only some mag 2-3 earthquakes along the path which weren't particularly unusual.

This one was sorta near Emily.
http://earthquake.usgs.gov/recenteqs...prP0519601.htm

Mag. 4.1

There was a 3.8 nearby two days ago too. Was Emily close enough then?

__________________
Hwæt! We Gardena in geardagum,
þeodcyninga, þrym gefrunon,
hu ða æþelingas ellen fremedon.

Of course this bigger one was no where near any hurricane or typhoon. Shows how hard it is to correlate these things.
But I'd worry about a tsunami.

http://earthquake.usgs.gov/recenteqs...kes/usana2.htm
Edit:
This says yes, we have no tsunami. We have no tsunami today.:
http://www.prh.noaa.gov/ptwc/hmsg

Another near Emily
http://neic.usgs.gov/neis/bulletin/neic_anbv.html