#Shaky Sands
2 messages in this thread
That disaster in Kobe reminded me of what one geologist once told me. He
said, that during a quake, structures built on bedrock fare better than built
on alluvial deposits (sand and clay).
I've only taken a "leisure course" in geology, so I don't claim any expertise
in this science. But, if what I was told is true, then all those filled-in
regions in SF bay, would be very bad places to be in the case of a major quake.
Frankly, if I live in San Francisco, I would prefer to live on the hilltops,
where bedrock is only a few feet below the topsoil.
Is my supposition right that rocky foundations result in less quake damage than
houses build on loose soil?
Leland in (non-seismic) Houston
Leland,
>> Is my supposition right that rocky foundations result in less quake damage
than houses build on loose soil? <<
In general, yes. How much more or less damage is done depends on the
specifics. In very loose soil like fill or old lakebeds, seismic waves of the
right frequency can make the soil act like a liquid. Anything built on such
liquefied soil won't stay standing very long.
OTOH, sink supports through soil to bedrock, and if you get a violent
back-and-forth motion in a quake, whiplash effect could do a lot of damage to
your solidly secured building.
Jon W.