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Science Forum Index » Geology - Earthquakes Forum » Floods in the NMSZ and earthquakes...
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| Belba Grubb... |
 Posted: Fri May 09, 2008 9:20 pm |
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Guest
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Just for fun, on a weather board I've been doing a day-by-day timeline
of the 1927 Mississippi River valley floods, and noticed today after
looking at some historical data of intraplate earthquakes at
http://earthquake.usgs.gov/research/data/scr_catalog.php that there
didn't seem to be an increase in activity in the New Madrid Seismic
Zone even when the flood was at its height, with the Mississippi River
some 70-80 miles wide below Memphis, the Mound Landing levee breached
and deep (10 to 30 feet) flood waters standing throughout the Yazoo
basin in Mississippi, and with much of southwestern Arkansas
experiencing similar flooding due to levee breaches on the Red and
other rivers.
Very generally, the times of most widely spread flooding in the area
were from roughly March through July of that year, though there was
plenty of localized flooding before and after those months. The flood
waters didn't totally recede until some time in September.
The only quake noted in the area, on this list, for 1927 happened on
May 7 (May 10 per some newspaper accounts, which also say that it woke
people up in five states). That frequency appears to be a bit low
compared to other years. Of course it could just be that people were
distracted by the flooding and other severe weather and didn't notice
small-magnitude tremors.
Could the flood actually have masked the tremors?
My guess would have been that if the flooding had any effect at all in
this region, it would have been due to the weight of standing water
for an extended period of time and there would have been an increase
in seismicity noted either during the flood or afterwards as a sort of
rebound effect when the waters receded (although this recession did
happen very gradually). That doesn't seem to have happened at all.
Just thought it was interesting.
Barb
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"Slander cannot destroy an honest man - when the flood recedes the
rock is there”
-- Chinese proverb |
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| Mike Williams... |
| Posted: Sat May 10, 2008 7:51 am |
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"Belba Grubb" <trungsisterfan at (no spam) yahoo.com> wrote in message
news:4fefd90c-3883-4b10-906c-1d98a067d956 at (no spam) d45g2000hsc.googlegroups.com...
Just for fun, on a weather board I've been doing a day-by-day timeline
of the 1927 Mississippi River valley floods, and noticed today after
looking at some historical data of intraplate earthquakes at
http://earthquake.usgs.gov/research/data/scr_catalog.php that there
didn't seem to be an increase in activity in the New Madrid Seismic
Zone even when the flood was at its height, with the Mississippi River
some 70-80 miles wide below Memphis, the Mound Landing levee breached
and deep (10 to 30 feet) flood waters standing throughout the Yazoo
basin in Mississippi, and with much of southwestern Arkansas
experiencing similar flooding due to levee breaches on the Red and
other rivers.
Very generally, the times of most widely spread flooding in the area
were from roughly March through July of that year, though there was
plenty of localized flooding before and after those months. The flood
waters didn't totally recede until some time in September.
The only quake noted in the area, on this list, for 1927 happened on
May 7 (May 10 per some newspaper accounts, which also say that it woke
people up in five states). That frequency appears to be a bit low
compared to other years. Of course it could just be that people were
distracted by the flooding and other severe weather and didn't notice
small-magnitude tremors.
Could the flood actually have masked the tremors?
My guess would have been that if the flooding had any effect at all in
this region, it would have been due to the weight of standing water
for an extended period of time and there would have been an increase
in seismicity noted either during the flood or afterwards as a sort of
rebound effect when the waters receded (although this recession did
happen very gradually). That doesn't seem to have happened at all.
Just thought it was interesting.
Barb
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"Slander cannot destroy an honest man - when the flood recedes the
rock is there”
-- Chinese proverb
I'm not familiar with the "source catalogs" used (your link), but, for the
period in question, I would guess the source of quake data was primarily
felt reports; the instrument network in that area must have been extremely
sparse. And, with only magnitudes >=4.5 reported, I would think that there,
for the short period involved, you would expect less than one quake of that
magnitude, no? I realize yours was an informal study, but is there any
statistical significance at all considering the few data points involved?
And I'm rather skeptical about the "weight of the standing water" theory.
Though, in places, the water would have been several meters deep,
regionally, or over the broad areas surrounding the fault(s), it would have
averaged a very few inches deep. The weight of that water would have
comprised a vanishingly small percentage of the total weight of the rock
column.
Occasional disclaimer: I'm not a professional in the fields of seismology or
geology.
Michael Williams
Arroyo Grande, CA U.S. |
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| Mike Williams... |
| Posted: Sat May 10, 2008 7:31 pm |
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Sorry for the lack of brackets to set off Belba's post. For some reason my
newsreader has stopped inserting them again. Yes, I've got all the proper
options set.
Mike Williams |
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| Skywise... |
| Posted: Sat May 10, 2008 10:41 pm |
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| Mike Williams... |
| Posted: Sun May 11, 2008 6:58 am |
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"Skywise" <into at (no spam) oblivion.nothing.com> wrote in message
news:zVtVj.12926$Lq4.12018 at (no spam) newsfe05.ams2...
Quote: "Mike Williams" <miklwlms at (no spam) pacbell.net> wrote in news:Z7rVj.3145$J16.1202
at (no spam) newssvr23.news.prodigy.net:
X-Newsreader: Microsoft Outlook Express 6.00.2900.3138
I'm of the opinion this is your problem.
Brian
You may well be right, Brian. But it IS the only problem I've had with the
program.
Beats Google Groups, anyway!
Mike Williams
Arroyo Grande, CA U.S. |
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| Jo Schaper... |
| Posted: Sun May 11, 2008 1:42 pm |
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Belba Grubb wrote:
Quote: Just for fun, on a weather board I've been doing a day-by-day timeline
of the 1927 Mississippi River valley floods, and noticed today after
looking at some historical data of intraplate earthquakes at
http://earthquake.usgs.gov/research/data/scr_catalog.php that there
didn't seem to be an increase in activity in the New Madrid Seismic
Zone even when the flood was at its height, with the Mississippi River
some 70-80 miles wide below Memphis, the Mound Landing levee breached
and deep (10 to 30 feet) flood waters standing throughout the Yazoo
basin in Mississippi, and with much of southwestern Arkansas
experiencing similar flooding due to levee breaches on the Red and
other rivers.
Very generally, the times of most widely spread flooding in the area
were from roughly March through July of that year, though there was
plenty of localized flooding before and after those months. The flood
waters didn't totally recede until some time in September.
The only quake noted in the area, on this list, for 1927 happened on
May 7 (May 10 per some newspaper accounts, which also say that it woke
people up in five states). That frequency appears to be a bit low
compared to other years. Of course it could just be that people were
distracted by the flooding and other severe weather and didn't notice
small-magnitude tremors.
Could the flood actually have masked the tremors?
My guess would have been that if the flooding had any effect at all in
this region, it would have been due to the weight of standing water
for an extended period of time and there would have been an increase
in seismicity noted either during the flood or afterwards as a sort of
rebound effect when the waters receded (although this recession did
happen very gradually). That doesn't seem to have happened at all.
Just thought it was interesting.
Barb
----------
Have you looked at the Nuttli catalog?
http://www.eas.slu.edu/Earthquake_Center/earthquake_dos.html
New Madrid quakes in excess of 3 can be readily felt, due to the terrain
and the fact that the area tends to ring like a bell for large
distances. The USGS >4.5 cutoff tends to leave out a lot of NMSZ activity.
Rather than mask quakes, I would think that standing water would amplify
the movement. We're in liquefaction country here. At the very least,
one might be able to see the water move in ponded areas, if one were
watching for such things.
1927 wasn't a good weather year around here. Most people have forgotten
the floods, but still remember the May 9 tornado that killed 82 in
Poplar Bluff and the F3 tornado that hit St. Louis Sept. 29, killing
about 75 people and destroying residential parts of city and county.
If you are looking for a more modern correlation, see what happens in eq
data if you look at April to August 1993. Most of that time, the
Mississippi was flooded into the lowlands.
We're already 8" over average rainfall this year with numerous floods;
hope not, but if it doesn't quit raining we're headed for another 1993. |
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| Skywise... |
| Posted: Mon May 12, 2008 12:54 am |
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Guest
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"Mike Williams" <miklwlms at (no spam) pacbell.net> wrote in
news:3cBVj.2431$ah4.321 at (no spam) flpi148.ffdc.sbc.com:
Quote:
"Skywise" <into at (no spam) oblivion.nothing.com> wrote in message
news:zVtVj.12926$Lq4.12018 at (no spam) newsfe05.ams2...
"Mike Williams" <miklwlms at (no spam) pacbell.net> wrote in
news:Z7rVj.3145$J16.1202 at (no spam) newssvr23.news.prodigy.net:
X-Newsreader: Microsoft Outlook Express 6.00.2900.3138
I'm of the opinion this is your problem.
Brian
You may well be right, Brian. But it IS the only problem I've had with
the program.
Beats Google Groups, anyway!
Of that I can't disagree.
I don't use Internet Exploder myself. But it is well known to
be a prime target of hackers and malicious code. That the program
is behaving erratically _could_ be a sign of a breach.
I realise it may involve learning new software but you should
try to get away from the stock MS programs.
Personally, I use Firefox, Thunderbird, and XNews. Nothing's
perfect, but these are widely regarded as being less imperfect.
Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes? |
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| Skywise... |
| Posted: Mon May 12, 2008 12:57 am |
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| Jo Schaper... |
| Posted: Mon May 12, 2008 7:23 am |
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Guest
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Skywise wrote:
Quote: Jo Schaper <jo345sch765aper at (no spam) s9ocket.net> wrote in news:
_aKdnbSyfKPGo7rVnZ2dnUVZ_uidnZ2d at (no spam) posted.socketinternetservices:
Snipola
Rather than mask quakes, I would think that standing water would amplify
the movement. We're in liquefaction country here.
hmmmmm.... does soil have to be wet to be subject to liquifaction?
Brian
I don't know that it *has* to be wet, but since liquefaction is the
shaking of a particulate matter to the point that it becomes
cohesionless and loses its load bearing strength, standing groundwater
that starts shaking can't hurt. What holds you up better, dry dirt or
mud? Quicksand is a sand bank with water moving through it. You can
easily walk on a damp beach with a semi-dry crust, but once the tide
starts coming in, there's that strip of goo right along the water as the
pores become saturated. |
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