PSN-L Email List Message

Subject: RE: Now I Am Confused - AGAIN
From: "Kareem J. Lanier" system98765@.............
Date: Sun, 5 Sep 2010 20:54:48 -0700


Well...

By Euan Smith's statement, he is also implying that other places which have
"soft soils" will experience or has experienced this same "shock absorbed
shaking". Was he comparing this to other similar sized quakes with similar
soil conditions? If so, what areas?  I would love to see how he came to that
conclusion. More details needed. 

we've all read those published papers from earthquake engineers discussing
the affects of heavy shaking or high accelerated motion caused by
earthquakes. From those papers, it's usually the larger or taller buildings
that are affected more so by the ground motion. I haven't seen any of the
pictures from that area but have read a lot of eyewitness accounts which
reported a good deal of heavy shaking. 




-----Original Message-----
From: psnlist-request@.............. [mailto:psnlist-request@...............
On Behalf Of Dave Nelson
Sent: Sunday, September 05, 2010 2:05 PM
To: psnlist@..............
Subject: Re: Now I Am Confused - AGAIN

Hey Jerry,
                  its a pretty complex subject,  and the amount of shaking 
and liquifaction
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 shaking
  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 went 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 fill with
water.

So the 3 factors above and others not mentioned all play a part in 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 city,  but 
the combination of the alluvial basin the city sat on,  the period of 
shaking  are what contributed to the horrific numbers of deaths and 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 contradiction to the 
>California EQ where soft ground cause liquefaction of the ground.
>
>The quote is as follows: "Euan Smith, professor of Geophysics at 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

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