Shaky Sands
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.