PSN-L Email List Message

Subject: New Zealand earthquake
From: Tangazazen@.......
Date: Mon, 6 Sep 2010 15:19:00 EDT



Hi All,
 
 
There has been some discussion  on the latest New Zealand earthquake  and 
considering the magnitude, luckily no loss of life but considerable damage.  
Most earthquake damage is due to the surface wave. The attenuation of 
Rayleigh  waves is significantly less than that of a body wave, approximately 1/ 
root of  distance.  For gravel and sands though, seismic velocity are low but 
the  dispersion can be quite high, that is the energy appears in lower and 
lower  frequency with distance. Certain types of clay particularly when wet 
can exhibit  thixotropic properties, that is a fall in viscosity with shear 
stress as at  Mexico city. Does anybody know of the geology of the area?
 
Resonance can be damaging to building and as a general rule of thumb is  
about 10 c/s divided by the number of floors.  Given the distance from the  
epicentre one would expect the taller building to have sustain the most  
damage.
Is there anybody in Christchurch who can though some light on any of  this? 


Martin Page





 
Hi All,
 
 
There has been some discussion  on the latest New Zealand earthq= uake=20 and considering the magnitude, luckily no loss of life but considerable da= mage.=20 Most earthquake damage is due to the surface wave. The attenuation of Rayl= eigh=20 waves is significantly less than that of a body wave, approximately 1/ roo= t of=20 distance.  For gravel and sands though, seismic velocity are low but= the=20 dispersion can be quite high, that is the energy appears in lower and lowe= r=20 frequency with distance. Certain types of clay particularly when wet can= exhibit=20 thixotropic properties, that is a fall in viscosity with shear stress as= at=20 Mexico city. Does anybody know of the geology of the area?
 
Resonance can be damaging to building and as a general rule of thumb= is=20 about 10 c/s divided by the number of floors.  Given the distance fro= m the=20 epicentre one would expect the taller building to have sustain the most=20 damage.
Is there anybody in Christchurch who can though some light on= any of=20 this?
 
Martin Page

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