The 50-day SMA (the orange line on this 4-Hr chart) had been acting as resistance for 6 months until BTC smashed through to the upside on 6 Jan 2019. Even with the $250 dump on 10 Jan, the 50D may turn to support, along with the shallower ascending trendline (yellow) connecting the local lows of 18 & 28 Dec 2018, and 1 Jan 2019.
If this doesn't hold, the next support may be around $3600 (steeper of the descending yellow trendline).
If this doesn't hold, the next support may be around $3600 (steeper of the descending yellow trendline).