Speaker earthquake protection and isolation

It all depends on where the epicenter is and where you are. My high school friend's father was an architectural stress engineer and he told me that if an 8.0 quake, centered under Los Angeles were to occur, nothing would be higher than about 2 feet. He designed structures to stay up as long as possible to get as many people out before total collapse. If the epicenter is many miles away, you're in a for a bit of luck. 
At that time, only the Morman Temple in Utah was built to withstand a direct 8.0 hit.

Also there's ground soil composition, terrain, and a host of other factors to consider. Where you live in Napa is a 35 mile fault that was discovered just after your encounter. There's not much one can do unless you're willing to quake proof your speakers but it won't look good. Tethers, wires mounted to walls or ceilings, and just how to mount them to the speakers, etc.

When the '71 Sylmar earthquake hit, my mom woke up my dad and said, "Tom, there's an earthquake!" to which my dad replied, "Back on Iwo Jima the sky was falling! Go back to sleep!", which he did. He was pragmatic when it came to the big stuff.

All the best,
Nonoise

You could try adding spikes to the bottom of the Corian.  If you place the spikes as close to the corners as possible, you've still got the larger footprint you were after.  I don't think the change in the height of the center of gravity will matter much as long as your don't use crazy long spikes. Dick

Hey kevine, I have a thought that may be helpful...

When we fostered a new kitten last year, I was concerned about both potty accidents affecting my speakers, and the possibility of the cat doing scratching and clawing at the base of the speakers.  So we placed decorative pillows around the bases of the speakers, the kind you buy at a Pier 1 or place like that.  Not pillows that look like they belong on a bed.   Sure enough, during play time one of our older cats got spooked and hit the base hard enough to knock it over, but the pillows were there and they cushioned the fall.   It wasn't even what I intended them to do, just an unexpected benefit.  Now, your Silverlines are larger than mine, but the same principle applies - if you can't keep them from toppling, make sure they topple onto something soft and forgiving.  It may seem odd - and I guess it is - but if you find decorative pillows that match or enhancer your listening room's decor, and you just sort of spread them around the speakers, next time they come down they may just land on pillows.  Best part is the pillows are temporary, they don't affect the integrity of the speaker cabinets, and they're at ground level so shouldn't change what you're hearing either.   My ex-wife's sister used to decorate with pillows all over her rooms, and it always made her place seem warm and homey, so I was just copying her!

i guess insurance is the best earthquake protection and isolation.

I can't believe I'm posting this again but this is your solution -

http://www.townshendaudio.com/hi-fi-home-cinema-equipment-vibration-isolation/seismic-isolation-bars...

I use them & they are a BIG improvement over spikes.

Thank you for your responses. Alan Yun said he did have one person connect a wire to his ceiling that ran down to the back of his speakers, where they were connected with a screw--this would not work with my wife. I might try the spikes at the bottom of the Corian, but I'm not sure how the Corian and Speaker should be connected as far as isolation goes. Pillows are an idea, but my wife has her own personal tastes of what she wants in the room. I looked at the seismic isolation bars, which look like they do a wonderful job for sound quality, but I don't see how they actually fasten to the speaker to prevent falling over--I emailed them to find out more details.