PSN-L Email List Message

Subject: Re: Seismic Signature of Tornadoes
From: Thomas Dick dickthomas01@.............
Date: Wed, 17 Apr 2013 20:59:28 -0500


On 4/17/2013 7:13 AM, chrisatupw@....... wrote:
> From: Thomas Dick  CC: David Dick ; Powell, Richard L
> ; sarah holland 
> Sent: Sun, 7 Apr 2013 16:05
> Subject: Seismic Signature of Tornadoes
>
>
> ****Since things are quiet on the network lately and even
> Geoff has commented on this subject in the past, I'd like to return
> to this issue......on Steve Jones' Facebook page,
> http://alabamaquake.com/reports.html#Tornado_Seismic_Signature
> a couple of paragraphs on the above issue surfaced lately. (Tornado
> Detection Based on Seismic Signal,” Tatom/Knupp/Vitton; 18 July 1994)
> I replied to his post with this:
>
> ****I got strongly criticized by the Paducah regional weather people and
> pulled back after the initial discussion on PSN network. But, I have
> spent many hours studying weather and what I see on the seismic
> equipment.  I learned to recognize the signatures of strong storms off
> the coast of Alaska, Great Lakes, east coast and off the SE coast of
> Greenland....even hurricanes in the Gulf. This is what I know. The Ohio
> group that suggested a peak around .15 to .25 Hz were seeing Great
> Lakes waves / wind....not a tornado. I have learned  what to expect on
> the N-S or E-W Lehman.
>
> ****Frank Tatom called the US array system to my attention. I examined
> the Harrisburg, ILL tornado data and felt it was too short of a path. I
> also did extensive study on the Henryville, IN  tornado which actually
> went over into Kentucky. I felt that the hilly terrain confuses the
> issue... it is still too early, we are still doing preliminary study /
> investigation work. I also used the USArray to look at the Oakland 
> City, IN
> macroburst.
>
> ****I honestly can't say I can put my finger on a specific frequency
> that fits all these situations. IU claimed they saw something in the
> Harrisburg data (which I believe), but it was more likely the collapse
> of the storm cell .... something like I saw on the Oakland City,
> IN macroburst.
>
> ****Tatom and Vitton were looking for a specific frequency;
> something that a detector could easily recognize. I really believe it
> exists. I suspect it to be higher than .2 Hz. I spent time interviewing
> people who experienced the tornado I brought to the PSN network
> for discussion.
>
> ****I did the same in conjunction with the Branson, MO tornado as well
> as Joplin, MO. If those who experienced these tornadoes say anything
> about hearing the tornado, they all agree it sounded somewhat like a
> train. Logically, this common thread of "sound" must be a clue to either
> higher or lower creator of the "sound" exists BUT NOT this .2 Hz. What
> we hear may even be harmonics of the original frequency.
>
> ****This last two sentences have haunted me all night. Sound is a
> common denominator. Have I missed something? Where do we look?
>
> Hi Tom,
>
>       Lets condider a tornado. It is a very violent spinning column of
> air, usually well over 1000 ft high. The outside of the column has a very
> high shear rate with the surrounding air, which will generate turbulent
> eddies. These are likely to be up to several times the diameter of the
> column long, but will otherwise break off independantly. This turbulence
> is likely to be most of what you hear, but seismic signals will mostly be
> generated by pressure variations close to the ground.

*OK, let me add a new twist to our discussion on tornadoes.....suppose 
the tornado has some of the characteriestics of a whistle*...*whistles 
differ in pitch, even when you blow hard or gentle, the sound is 
different -- and you even can get **whistles* *you can't hear but dogs 
can! Suppose the tornado acts like a whistle*?
>    Remember that you will NOT hear any Infrasound signals !
>    I suggest that comparing seismic recordings with Infrasound
> recordings could be a more rewarding, than with storm cloud effects ?
> It is not disputed that cold fronts and storm cells can produce seismic
> signals. I am not familiar with the frequency / period ranges of those
> signals, but the cloud bases are several thousand feet above ground,
> so the period is likely to be quite long.
>    Tornadoes generate severe turbulence, but, critically, they are in
> direct contact with the ground, so the frequencies could be quite high.
> Consider a tornado of 220 yards diameter moving at 40 mph -- it will
> cross a given point in about 11 seconds. The frequency of signals due
> to the pressure eddies is likely to be much higher
*Those people I talked to NEVER mention**ed "feeling" a low frequency 
vibration in their feet.*
> .
>     Are there any figures for the sort of pressure reduction that is
> observed at the centre of a tornado ?
>    A tornado may well generate characteristic sound signals,
> but it is more likely that they will be a bit different for different
> sized tornadoes, with different tracking speeds and that they
> will change with time as the tornado grows and later decays.
>     What was the damage width of the track of the tornado you
> experienced ? In the photos that I have seen they have just
> effected a few streets - certainly not 1/2 a mile.
>
>    Regards,
>
>     Chris
>


  
    
  
  
    
On 4/17/2013 7:13 AM, chrisatupw@....... wrote:
From: Thomas Dick <dickthomas01@.............
CC: David Dick <daviddick@...........>; Powell, Richard L
<rlpowell@...........>; sarah holland <Shteacherlady@.........>
Sent: Sun, 7 Apr 2013 16:05
Subject: Seismic Signature of Tornadoes


****Since things are quiet on the network lately and even
Geoff has commented on this subject in the past, I'd like to return
to this issue......on Steve Jones' Facebook page,
http://alabamaquake.com/reports.html#Tornado_Seismic_Signature
a couple of paragraphs on the above issue surfaced lately. (Tornado
Detection Based on Seismic Signal,” Tatom/Knupp/Vitton; 18 July 1994) 
I replied to his post with this:

****I got strongly criticized by the Paducah regional weather people and
pulled back after the initial discussion on PSN network. But, I have
spent many hours studying weather and what I see on the seismic
equipment.  I learned to recognize the signatures of strong storms off
the coast of Alaska, Great Lakes, east coast and off the SE coast of
Greenland....even hurricanes in the Gulf. This is what I know. The Ohio
group that suggested a peak around .15 to .25 Hz were seeing Great
Lakes waves / wind....not a tornado. I have learned  what to expect on
the N-S or E-W Lehman.

****Frank Tatom called the US array system to my attention. I examined
the Harrisburg, ILL tornado data and felt it was too short of a path. I
also did extensive study on the Henryville, IN  tornado which actually
went over into Kentucky. I felt that the hilly terrain confuses the
issue... it is still too early, we are still doing preliminary study /
investigation work. I also used the USArray to look at the Oakland City, IN
macroburst.

****I honestly can't say I can put my finger on a specific frequency
that fits all these situations. IU claimed they saw something in the
Harrisburg data (which I believe), but it was more likely the collapse
of the storm cell .... something like I saw on the Oakland City,
IN macroburst.

****Tatom and Vitton were looking for a specific frequency;
something that a detector could easily recognize. I really believe it
exists. I suspect it to be higher than .2 Hz. I spent time interviewing
people who experienced the tornado I brought to the PSN network
for discussion.

****I did the same in conjunction with the Branson, MO tornado as well
as Joplin, MO. If those who experienced these tornadoes say anything
about hearing the tornado, they all agree it sounded somewhat like a
train. Logically, this common thread of "sound" must be a clue to either
higher or lower creator of the "sound" exists BUT NOT this .2 Hz. What
we hear may even be harmonics of the original frequency.

****This last two sentences have haunted me all night. Sound is a
common denominator. Have I missed something? Where do we look?

Hi Tom,

      Lets condider a tornado. It is a very violent spinning column of
air, usually well over 1000 ft high. The outside of the column has a very
high shear rate with the surrounding air, which will generate turbulent
eddies. These are likely to be up to several times the diameter of the
column long, but will otherwise break off independantly. This turbulence
is likely to be most of what you hear, but seismic signals will mostly be
generated by pressure variations close to the ground.

OK, let me add a new twist to our discussion on tornadoes.....suppose the tornado has some of the characteriestics of a whistle...whistles differ in pitch, even when you blow hard or gentle, the sound is different -- and you even can get whistles you can't hear but dogs can! Suppose the tornado acts like a whistle?
   Remember that you will NOT hear any Infrasound signals !
   I suggest that comparing seismic recordings with Infrasound
recordings could be a more rewarding, than with storm cloud effects ?
It is not disputed that cold fronts and storm cells can produce seismic
signals. I am not familiar with the frequency / period ranges of those
signals, but the cloud bases are several thousand feet above ground,
so the period is likely to be quite long.
   Tornadoes generate severe turbulence, but, critically, they are in
direct contact with the ground, so the frequencies could be quite high.
Consider a tornado of 220 yards diameter moving at 40 mph -- it will
cross a given point in about 11 seconds. The frequency of signals due
to the pressure eddies is likely to be much higher
Those people I talked to NEVER mentioned "feeling" a low frequency vibration in their feet.
.
    Are there any figures for the sort of pressure reduction that is
observed at the centre of a tornado ?
   A tornado may well generate characteristic sound signals,
but it is more likely that they will be a bit different for different
sized tornadoes, with different tracking speeds and that they
will change with time as the tornado grows and later decays.
    What was the damage width of the track of the tornado you
experienced ? In the photos that I have seen they have just
effected a few streets - certainly not 1/2 a mile.

   Regards,

    Chris



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