PSN-L Message - Subject: RE: Now I Am Confused

To describe a system that vibrates one can write an equation to describe = that vibration. A means to solve the equation would be to use Eigen's method resulting in the=20 =20 Eigenmodes or Eigenvectors and Eigenvalues. =20 Eigenmodes and or Eigenvectors are the shapes of the system undergoing vibration and the Eigenvalues, typically sovled for, are the natural frequencies of the system. The lowest value of which is called the fundamental frequency or first natural frequency. =20 =20 Based on the context used, I would take it to mean that the earth was vibrating in many, many different shapes. This is certainlyt possible gi= ven the make up of the ground (soil) or different rock in the mantle and deep= er. =20 I should mention that the Eigenmode is not equal to the resonance frequen= cy at all. Rather the one of the eigenvalues of the system can be the reson= ance frequency. =20 I hope this helps shed some light on the matter. =20 Best Regards =20 ________________________________ From: psnlist-request@.............. on behalf of Geoffrey Sent: Mon 9/6/2010 12:57 AM To: psnlist@.............. Subject: Re: Now I Am Confused - AGAIN Also, Simply To Be Verbose, It is my understanding that Eigen mode is simply a fancy way of saying There is a fundamental sympathetic SYSTEM resonant frequenc= y. It applies to any mechanical system regardless how complex its physical makeup. It has always seems so silly to me that people don't just say resonates instead of always having to give credit to people who in the past have simply stated the obvious. If you need to cite a genuine mathematical set of equations then I understand the reference to Eigen who was most probably some famous dead person from the distant past. So like the earth/ground showed a natural resonance at whatever period or= frequency. Resonance means so much more to me than Eigen anything which requires a university degree to understand. If you are a history buff then I understand all those references to peoples of the past. Ill bet [speculatively only] if you could give planet earth a shove into = the sun Then, let it go, then it might have a resonant frequency as it re stabilizes in its orbit, Now what would you call such a thing as that ??? Earth Eigen Mode or some kind of resonance for the Earth/Moon/Sun System. You get a wavelike motion as the Earth/Moon orbits the Sun. Mother Nature has done everything man has done a billion years before man came along. Why give credit to man any more than the Dollars of pay for his work. Please, Just call it, "Resonance" Then I don't need to look up anything e= lse. If you do that, I will not have to say "Lee De Forest Electron Valve" wh= en talking about a simple Triode vacuum tube. Although I have heard of Earthquake accelerations in excess of 32F/s^2 wh= ich makes two ton boulders hop out of their places and move quite a good number of feet, I have never heard of= well dampened soil such as youse-guys have talked about in that recent NZ EQ. It [The Ground ] seems to have functioned like a giant automobile shock absorber. Best Regards, geoff -------------------------------------------------- From: "Kay Wyatt" Sent: Monday, September 06, 2010 2:26 AM To: Subject: Re: Now I Am Confused - AGAIN > Mark, > > Can you explain the following sentence from your email... > > "Eigenmode activity was observed sporadically over the week leading up = to > the > main quake." > > Sorry for my ignorance. Thanks muchly! > > Kay > > > ----- Original Message ----- > From: "Mark Robinson" > To: > Sent: Sunday, September 05, 2010 3:51 PM > Subject: Re: Now I Am Confused - AGAIN > > >> NZ's geological service has a page up on the quake at >> >>> http://www.geonet.org.nz/news/article-sep-4-2010-christchurch-earthquake.= html >> >> It includes maps and photographs showing the surface rupture which is >> variously reported as 13 and 22km in length. Lateral displacements up = to >> 4m have been measured and are evident in the photographs. >> >> The main event report is at >> >> http://www.geonet.org.nz/earthquake/quakes/3366146g.html >> >> while the following link provides felt reports from the general public= as >> well as measured peak ground accelerations and velocities >> >> http://www.geonet.org.nz/earthquake/quakes/3366146g-shaking.html >> >> There have been in excess of 80 significant aftershocks (>mag3) since = the >> main event and the rest of the country is showing high levels of >> background activity with significant volcanic tremor in the volcanic >> plateau of the North Island and unusual levels of seismic noise across= the >> country. >> >> Eigenmode activity was observed sporadically over the week leading up = to >> the main quake. >> >> The damage has been compounded by heavy rain and strong winds. >> >> The army has been deployed to enforce a cordon around the Christchurch= CBD >> while isolated disorder is being reported as people try to access >> supermarkets and pharmacy services. >> >> Official instructions to not attend the hospitals except in cases of >> serious emergency leave residents in a Catch-22 as doctors and other s= mall >> businesses are instructed not to open until their premises have been >> inspected by structural engineers. >> >> There is considerable damage to the water and sewerage systems with 20= % of >> Christchurch having no water supply. This will take a long time to rep= air. >> >> All schools are closed until at least Wednesday. >> >> A selection of local media >> >> http://www.nzherald.co.nz/?c_id=3D1502981 >> http://www.scoop.co.nz/ >> http://www.stuff.co.nz/ >> http://tvnz.co.nz/national-news >> http://www.3news.co.nz/ >> http://www.radionz.co.nz/news >> >> >> On 06/09/10 09:20, GPayton wrote: >>> Dave, I am so glad that you answered, being from NZ. I was hoping tha= t >>> you would. >>> When the quake occurred, I looked at Google Earth and it appeared tha= t >>> the area was mountainous, but that software can be misleading sometim= es. >>> Thank you for the input. I suspect the ground acted like a "wet spong= e" >>> then. >>> Best regards, >>> Jerry >>> ----- Original Message ----- >>> *From:* Dave Nelson >>> *To:* psnlist@.............. >>> *Sent:* Sunday, September 05, 2010 4:04 PM >>> *Subject:* Re: Now I Am Confused - AGAIN >>> >>> Hey Jerry, >>> its a pretty complex subject, and the amount of shaking >>> and liquefaction >>> is proportion to a number of things, including.... >>> distance from the quake .... attenuation of the waves >>> magnitude of the quake .... size affects the period of severe sha= king >>> soil type .... soft, hard, gravels etc etc >>> >>> I know Christchurch city very well, having worked there, visited >>> there many >>> times >>> over the years and my 2 kids (early 20's) still live there and we= nt >>> through >>> this quake. >>> A large portion of Christchurch is basically built on a swamp, it= is >>> very >>> soft wet soils >>> being an estuary area of 2 rivers. >>> When I worked for telecom there and were doing cable laying, you >>> only had >>> to dig >>> down a couple of feet and you holes/trenches started to slowly fi= ll >>> with water. >>> >>> So the 3 factors above and others not mentioned all play a part i= n >>> how much >>> damage is going to occur. >>> Magnitude therefore period of intense shaking is very signif. as >>> they found >>> out in that >>> huge quake in mexico in 1985 the M8.1 was a long way from the cit= y, >>> but >>> the combination of the alluvial basin the city sat on, the period= of >>> shaking are what contributed to the horrific numbers of deaths an= d >>> severe >>> damage (not to mention the crappy building construction) >>> REMEMBER ... New Zealand is pretty anal about earthquake >>> prepardness... >>> very strict building codes etc etc >>> >>> cheers >>> Dave Nelson >>> Sydney >>> Ex New Zealand >>> >>> At 12:21 AM 6/09/2010, you wrote: >>> >I was just reading an article about damages from the recent New= >>> Zealand >>> >EQ. I saw the following quote which seemed to be a contradictio= n >>> to the >>> >California EQ where soft ground cause liquefaction of the groun= d. >>> > >>> >The quote is as follows: "Euan Smith, professor of Geophysics a= t >>> Victoria >>> >University, speculated that the very soft soils of Christchurch= >>> had "acted >>> >like a shock absorber over a short period ... doing less damage= to >>> smaller >>> >buildings." >>> > >>> >Is this just a matter of less water content in the soils? >>> > >>> >Jerry >> >> __________________________________________________________ >> >> Public Seismic Network Mailing List (PSNLIST) >> >> To leave this list email PSNLIST-REQUEST@.............. with the body = of >> the message (first line only): unsubscribe >> See http://www.seismicnet.com/maillist.html for more information. >> > > __________________________________________________________ > > Public Seismic Network Mailing List (PSNLIST) > > To leave this list email PSNLIST-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSNLIST) To leave this list email PSNLIST-REQUEST@.............. with the body of the message (first line only): unsubscribe See http://www.seismicnet.com/maillist.html for more information. NOTICE - This communication may contain confidential and privileged infor= mation that is for the sole use of the intended recipient. Any viewing, c= opying or distribution of, or reliance on this message by unintended reci= pients is strictly prohibited. If you have received this message in error= , please notify us immediately by replying to the message and deleting it= from your computer. Re: Now I Am Confused - AGAIN=0A=0A<= META content=3D"MSHTML 6.00.6000.17037" name=3DGENERATOR>=0A= =0A

=0A

To describe a system that vibrates on= e can write an equation to describe that vibration. A means to solv= e the equation would be to use Eigen's method resulting in the =0A

=0AEigenmodes or Eigenvectors

=0A

and Eigenvalues.=0A

=0A<= DIV dir=3Dltr>Eigenmodes and or Eigenvectors = are the shapes of the system undergoing vibration and the Eigenvalues, ty= pically sovled for, are the natural frequencies of the system. The = lowest value of which is called the fundamental frequency or first natura= l frequency.

=0A

Bas= ed on the context used, I would take it to mean that the earth was vibrat= ing in many, many different shapes. This is certainlyt possible giv= en the make up of the ground (soil) or different rock in the mantle and d= eeper.

=0A

&= nbsp;

=0A

I should mention= that the Eigenmode is not equal to the resonance frequency at all. = Rather the one of the eigenvalues of the system can be the resonance fre= quency.

=0A

I hope this hel= ps shed some light on the matter.

=0A

Best Regards

=0A

=0AFrom: psnlist-request@webtronic= s.com on behalf of Geoffrey
Sent: Mon 9/6/2010 12:57 AM
T= o: psnlist@..............
Subject: Re: Now I Am Confused - = AGAIN

=0A

Also, Simply To Be= Verbose,
It is my understanding that Eigen mode is simply a fancy
= way of saying There is a fundamental sympathetic SYSTEM resonant frequenc= y.
It applies to any mechanical system regardless how complex its phys= ical makeup.
It has always seems so silly to me that people don't just= say
resonates instead of always having to give credit to
people wh= o in the past have simply stated the obvious.
If you need to cite a ge= nuine mathematical set of equations
then I understand the reference to= Eigen who was most probably
some famous dead person from the distant = past.
So like the earth/ground showed a natural resonance at whatever = period or frequency.
Resonance means so much more to me than Eigen any= thing which requires
a university degree to understand. If you are a h= istory buff then I understand
all those references to peoples of the p= ast.
Ill bet [speculatively only] if you could give planet earth a sho= ve into the sun
Then, let it go,
then it might have a resonant freq= uency as it re stabilizes in
its orbit, Now what would you call such a= thing as that ???
Earth Eigen Mode or some kind of resonance for the<= BR>Earth/Moon/Sun System. You get a wavelike motion
as the Earth/Moon = orbits the Sun.
Mother Nature has done everything man has done
a bi= llion years before man came along.
Why give credit to man any more tha= n the Dollars of pay for his work.
Please, Just call it, "Resonance" T= hen I don't need to look up anything else.
If you do that, I wil= l not have to say "Lee De Forest Electron Valve" when talking about a sim= ple Triode vacuum tube.

Although I have heard of Earthquake accele= rations in excess of 32F/s^2 which makes two ton boulders hop out of
t= heir places and move quite a good number of feet, I have never hear= d of well dampened
soil such as youse-guys have talked about in that r= ecent NZ EQ. It [The Ground ]
seems to have functioned like a giant au= tomobile shock absorber.

Best Regards,
geoff

---= -----------------------------------------------
From: "Kay Wyatt" <= kwyatt@.............>
Sent: Monday, September 06, 2010 2:26 AM
T= o: <psnlist@..............>
Subject: Re: Now I Am Confused - AGA= IN

> Mark,
>
> Can you explain the following senten= ce from your email...
>
> "Eigenmode activity was observed sp= oradically over the week leading up to
> the
> main quake.">
> Sorry for my ignorance. Thanks muchly!
>
&g= t; Kay
>
>
> ----- Original Message -----
> From:= "Mark Robinson" <mark.robinson@...............>
> To: <ps= nlist@..............>
> Sent: Sunday, September 05, 2010 3:51 PM=
> Subject: Re: Now I Am Confused - AGAIN
>
>
>&g= t; NZ's geological service has a page up on the quake at
>>
&= gt;>> http://www.geonet.org.nz/news/article-sep-4-= 2010-christchurch-earthquake.html
>>
>> It includes= maps and photographs showing the surface rupture which is
>> va= riously reported as 13 and 22km in length. Lateral displacements up to>> 4m have been measured and are evident in the photographs.
&g= t;>
>> The main event report is at
>>
>> http:/= /www.geonet.org.nz/earthquake/quakes/3366146g.html
>>
>= ;> while the following link provides felt reports from the general pub= lic as
>> well as measured peak ground accelerations and velocit= ies
>>
>> http://www.geonet.org.nz/earthquake/quake= s/3366146g-shaking.html
>>
>> There have been in ex= cess of 80 significant aftershocks (>mag3) since the
>> main = event and the rest of the country is showing high levels of
>> b= ackground activity with significant volcanic tremor in the volcanic
&g= t;> plateau of the North Island and unusual levels of seismic noise ac= ross the
>> country.
>>
>> Eigenmode activity = was observed sporadically over the week leading up to
>> the mai= n quake.
>>
>> The damage has been compounded by heavy = rain and strong winds.
>>
>> The army has been deployed= to enforce a cordon around the Christchurch CBD
>> while isolat= ed disorder is being reported as people try to access
>> superma= rkets and pharmacy services.
>>
>> Official instruction= s to not attend the hospitals except in cases of
>> serious emer= gency leave residents in a Catch-22 as doctors and other small
>>= ; businesses are instructed not to open until their premises have been>> inspected by structural engineers.
>>
>> Ther= e is considerable damage to the water and sewerage systems with 20% of>> Christchurch having no water supply. This will take a long time= to repair.
>>
>> All schools are closed until at least= Wednesday.
>>
>> A selection of local media
>>= ;
>> http:= //www.nzherald.co.nz/?c_id=3D1502981
>> http://www.scoop.co.nz/
>> http://www.stuff.co.nz/
>> http://tvnz.co.nz/national-news
>= > http://www.3news.co.nz/
&= gt;> http://www.radionz.co.n= z/news
>>
>>
>> On 06/09/10 09:20, GPayton= wrote:
>>> Dave, I am so glad that you answered, being from = NZ. I was hoping that
>>> you would.
>>> When the= quake occurred, I looked at Google Earth and it appeared that
>>= ;> the area was mountainous, but that software can be misleading somet= imes.
>>> Thank you for the input. I suspect the ground acted= like a "wet sponge"
>>> then.
>>> Best regards,<= BR>>>> Jerry
>>>     ----- Origi= nal Message -----
>>>     *From:* Dave Ne= lson <mailto:dave.nelso= n@...............>
>>>     *To:* p= snlist@.............. <mailt= o:psnlist@..............>
>>>     = *Sent:* Sunday, September 05, 2010 4:04 PM
>>>  &nb= sp; *Subject:* Re: Now I Am Confused - AGAIN
>>>
>= ;>>     Hey Jerry,
>>>  &= nbsp; its a pretty complex subject, and the amount of shaking
&g= t;>>     and liquefaction
>>> =     is proportion to a number of things, including....
= >>>     distance from the quake .... attenua= tion of the waves
>>>     magnitude of th= e quake .... size affects the period of severe shaking
>>>&nb= sp;    soil type .... soft, hard, gravels etc etc
>&= gt;>
>>>     I know Christchurch city = very well, having worked there, visited
>>>   = there many
>>>     times
>&g= t;>     over the years and my 2 kids (early 20's) = still live there and went
>>>     through=
>>>     this quake.
>>> = ;    A large portion of Christchurch is basically built on= a swamp, it is
>>>     very
>>&= gt;     soft wet soils
>>>  &nb= sp; being an estuary area of 2 rivers.
>>>  &= nbsp; When I worked for telecom there and were doing cable laying, = you
>>>     only had
>>> = ;    to dig
>>>     down a= couple of feet and you holes/trenches started to slowly fill
>>= >     with water.
>>>
>>>&= nbsp;    So the 3 factors above and others not mentioned a= ll play a part in
>>>     how much
>= ;>>     damage is going to occur.
>>&g= t;     Magnitude therefore period of intense shaking = is very signif. as
>>>     they found
= >>>     out in that
>>> &nb= sp;   huge quake in mexico in 1985 the M8.1 was a long way from= the city,
>>> but
>>>     th= e combination of the alluvial basin the city sat on, the period of
>= ;>>     shaking are what contributed to the hor= rific numbers of deaths and
>>>     sever= e
>>>     damage (not to mention the crap= py building construction)
>>>     REMEMBE= R ... New Zealand is pretty anal about earthquake
>>> prepard= ness...
>>>     very strict building code= s etc etc
>>>
>>>     cheers<= BR>>>>     Dave Nelson
>>> =     Sydney
>>>     Ex New = Zealand
>>>
>>>     At 12:21 = AM 6/09/2010, you wrote:
>>>      &g= t;I was just reading an article about damages from the recent New
>= >>     Zealand
>>>   = ;   >EQ. I saw the following quote which seemed to be a cont= radiction
>>>     to the
>>>&= nbsp;     >California EQ where soft ground cause l= iquefaction of the ground.
>>>      = >
>>>      >The quote is as fo= llows: "Euan Smith, professor of Geophysics at
>>>  = ;   Victoria
>>>      >= University, speculated that the very soft soils of Christchurch
>&g= t;>     had "acted
>>>  &nbs= p;   >like a shock absorber over a short period ... doing le= ss damage to
>>>     smaller
>>&= gt;      >buildings."
>>> &n= bsp;    >
>>>     = >Is this just a matter of less water content in the soils?
>>= ;>      >
>>>   = ;   >Jerry
>>
>> _________________________= _________________________________
>>
>> Public Seismic = Network Mailing List (PSNLIST)
>>
>> To leave this list= email PSNLIST-REQUEST@.............. with the body of
>> the me= ssage (first line only): unsubscribe
>> See http://www.seismicnet.com/maillist.html for more information.
>>
>
> ____________________= ______________________________________
>
> Public Seismic Net= work Mailing List (PSNLIST)
>
> To leave this list email PSNL= IST-REQUEST@.............. with
> the body of the message (first li= ne only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more informa= tion.
>
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