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 sometimes.

Thank you for the input.  I suspect the ground acted like a "wet sponge" 
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 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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Dave, I am so glad that you answered, being from NZ.  I was =
hoping=20
that you would.
 
When the quake occurred, I looked at Google Earth and it appeared =
that the=20
area was mountainous, but that software can be misleading =
sometimes.
 
Thank you for the input.  I suspect the ground acted like a =
"wet=20
sponge" then.
 
Best regards,
Jerry
 

  
----- Original Message ----- 
  From:=20
  Dave Nelson 
  
To: psnlist@.............. =

  
Sent: Sunday, September 05, =
2010 4:04=20
  PM
  
Subject: Re: Now I Am Confused =
-=20
  AGAIN
  

Hey=20
  =
Jerry,
          &nb=
sp;      =20
  its a pretty complex subject,  and the amount of shaking 
and=20
  liquefaction
is proportion to a number of  things,=20
  including....
  distance from the quake  ....  =
attenuation=20
  of the waves
  magnitude of the quake  .... size affects =
the=20
  period of severe shaking
  soil type   ....  =
soft,=20
  hard, gravels etc etc

I know Christchurch city very well, =
having worked=20
  there, visited there many 
times
over the years and my 2 kids =
(early=20
  20's) still live there and went through 
this quake.
A large =
portion of=20
  Christchurch is basically built on a swamp, it is very 
soft wet=20
  soils
being an estuary area of 2 rivers.
When I worked for =
telecom there=20
  and were doing cable laying,  you only had 
to dig
down a =
couple of=20
  feet and you holes/trenches started to slowly fill with =
water.

So the 3=20
  factors above and others not mentioned all play a part in how =
much
damage=20
  is going to occur.
Magnitude therefore period of intense shaking is =
very=20
  signif. as they found 
out in that
huge quake in mexico in =
1985 =20
  the M8.1 was a long way from the city,  but 
the combination =
of the=20
  alluvial basin the city sat on,  the period of 
shaking  =
are what=20
  contributed to the horrific numbers of deaths and severe 
damage =
(not to=20
  mention the crappy building construction)
   REMEMBER ... =
New=20
  Zealand is pretty anal about earthquake prepardness...
very strict =
building=20
  codes  etc etc

cheers
Dave Nelson
Sydney
Ex New=20
  Zealand


At 12:21 AM 6/09/2010, you wrote:
>I was just =
reading=20
  an article about damages from the recent New Zealand 
>EQ.  =
I saw=20
  the following quote which seemed to be a contradiction to the=20
  
>California EQ where soft ground cause liquefaction of the=20
  ground.
>
>The quote is as follows: "Euan Smith, professor =
of=20
  Geophysics at Victoria 
>University, speculated that the very =
soft soils=20
  of Christchurch had "acted 
>like a shock absorber over a short =
period=20
  ... doing less damage to smaller 
>buildings."
>
>Is =
this=20
  just a matter of less water content in the=20
  =
soils?
>
>Jerry

______________________________________=
____________________

Public=20
  Seismic Network Mailing List (PSNLIST)

To leave this list email =
PSNLIST-REQUEST@SEISMICNET=
..COM=20
  with 
the body of the message (first line only): unsubscribe
See =
http://www.seismicnet.co=
m/maillist.html=20
  for more information.