As I indicated a week ago, Nasdaq had an opportunity to complete a Head & Shoulders (or a Double Top) pattern: https://investingangles.com/2021/02/25/nasdaq-candles-speak-25-02-2021/
Today the index closed below the indicated neck level. If tomorrow it continues aggressively downwards, the pattern would be confirmed. In that case, the minimum calculated target for the correction would be 11550 or 17% off the top. The would be a possibility to fall to 10600 (24%) or lower – it would depend on the index behavior around 11550 area.
I believe that the other major indices will follow. However, at this point there is no clear pattern to accurately measure the depth of their correction.