Notice where the 50-SMA is - at -837. This indicator usually bounces at the place where I've drawn the horizontal lines (-1000, -1250).
As you can see, the 50SMA will not be much of an early warning sign, and the price action could well have already dropped a good 50-75% of the eventual drop by the time it is hit.
Note the trendline that stopped turned the index back down.
Note the rising support on the chart also. That could be a target for the next low.