A good, but perhaps expensive suggestion would be to use "Inertial
Dampers".  I do not know if you have watched many of the Discovery
channel programs on how they were able to "earthquake" proof old
historically valued buildings, but the principles can apply to the
carousel as well.  As it IS in itself a historically valued structure.
What an inertial damper is really is a large ball bearing that sits in
a bowl and will allow anything attached to the ball's socket to move
all up and down the bowl.  So basically if the bowl is located on the
"unstable" ground. and the ball socket is attached to a concrete slab,
basically if there is any movement in the ground, the slab will appear
to be stationary during any ground movement.  When the ground stops
moving the ball bearings just settle back down in their rest position.

Probably what would have to be done is the carousel and it's building
would have to be raised up from the ground, or alternatively, the new
slab built in a new location where you would dig much deeper into the
ground and make a sort of foundation.  In here is where the "dish"
part of the dampers will be located.  A concrete slab would be lowered
in place and the ball sockets attached to it.  Now you have a free
floating slab and the building and carousel can be moved on top of the
slab.

There will be a space around the front of the building, but platforms
could be installed with movable plates that would allow the structure
to move.

I know that this is not a cheap venture, but the consequences of
loosing an original Looff carousel is unacceptable.

Unfortunately, this may be the only way to save the carousel.  There
is a cheaper alternative and that is to just isolate the carousel's
center resting point alone, but then again, what if the building around
it comes down?  If the building too is of historic value, then it along
with the carousel should be preserved.

Just a suggestion from a Discovery Channel lover.

Geo