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Re: Redwood Tree Seismic Hazard ?

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Barry,

Here in the Pacific NW, we have our share of problems 
with tree foundation failures during windstorms.  Most of 
this has been traced to an inherent instability problem of 
not having adequate overturning resistance  in the supporting soil. 
Other investigators have determined the root of the problem may be 
the structural elements of the tree foundation itself.

Local building officials have met with the designer, Ms. Mother 
Nature, but have not been able to come to a mutually acceptable 
conclusion.  When the matter was submitted to the Board of 
Registration for Engineers, counsel for Ms. Nature challenged the 
venue, claiming the matter was more appropriate for the Landscape 
Architecture Board. While this jurisdictional issue is being 
resolved, Ms. Nature has been allowed continue her growing practice 
of tree design.

The seismic response of trees is probably not too much of a 
problem due to the period of the ground motion and the 
fundamental period of the tree.  Perhaps a large tree house 
would change the trees fundamental response to that of an inverted 
pendulum, but I speculate.  Professor Spot Tedowl, 
University of Washington Paul Bunyon Chair, had thought about 
performing extensive studies of this issue but lack of funding and 
quick logging forced him to change his plans.

I believe several years back, the Dutch structural engineer, O. ver 
Design, looked into designing houses to withstand arboreal impact, 
but concluded that a chainsaw and common sense usually resolved the 
issue.

Greg