PSN-L Email List Message
Subject: Re: Now I Am Confused - AGAIN
From: "GPayton" gpayton@.............
Date: Sun, 5 Sep 2010 16:20:22 -0500
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
__________________________________________________________
Public Seismic Network Mailing List (PSNLIST)
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See http://www.seismicnet.com/maillist.html for more information.
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 -----
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.
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