Weird spikes after hours?!

[sdaconsulting]

Occasionally I have seen huge price spikes (on stocks that went down big during the day session) or huge price "cliffs" (on stocks that went up big during the day session).

For example, yesterday in the afternoon there were 3 huge spikes on GOOG, and multiple spikes also seen on many other big losers like CSCO, AMZN, EBAY a smaller one on AAPL. I should have taken some screen shots.

The pattern is that the stock spikes up, often all the way to the previous day's close, then rapidly falls back to its previous level. Sometimes there are multiple "spikes".

I've seen these on big days before.

My feeling is that someone is generating some kind of afterhours puts / calls options for BIG clients and wants to be hedged, and is making enough $$ to seriously overpay for the common in the afterhours market.

Anyone know more about these "spikes"?

Also, is there a source for historical afterhours price graphs? I have TD Ameritrade regular and Izone accounts and so far the only way I know to see afterhours graphs is to log in and look at the "research-> Stock" option, which only shows afterhours or premarket for today.

 

[foredog]

Don't know about US stock but in UK it can be a trade booked/changed after hours, so it may have been dealt at 10am but not booked until the market closed at 5pm. If you look at a daily bar of some UK stocks they will show it close at 475 (for example) but on a 4hour chart the time period finishes at 5pm so it may show that the close at that period is 499 because someone booked a late trade at 1645 and effectively created a fals price, but this will be show on the 4hr chart.

Hope this helps a little