I'd say a thousand point drop in a week would just about do this. It would snowball and be self-sustaining.
Use stop loss sell orders....Sell short if the market corrects...It is the down 500 or 1000 points in. A day that will kill you...never listen to your stock broker if you have..I lost a lot years ago ...when in doubt get out
Japan (world's 3rd largest economy) is hanging by a thread. I have said for a long time that this market is way overvalued, and I wouldn't be surprised to see a 50% correction. Biggest question now is which domino will fall first. Japan, EURO drop, China bond liquidation, or it may be as simple as 2 or 3 Big name DOW stocks significantly missing earnings targets.
Still, I disagree with the doom and gloomers of a STHF scenario. The 50% correction that could happen can be tempered with wise investing. There is a big difference when your portfolio drops 30% vs. 80%