(Updates to 4 pm)

NEW YORK, Oct 9 (Reuters) - U.S stocks tumbled for a seventh straight session on Thursday as investors bet recent moves by authorities worldwide to thaw frozen credit markets would not be enough to avert a global recession.

The Dow Jones industrial average .DJI sank 668.40 points, or 7.22 percent, to end unofficially at 8,589.70, based on the latest available data. The Standard & Poor's 500 Index .SPX tumbled 74.58 points, or 7.57 percent, to finish unofficially at 910.36. The Nasdaq Composite Index .IXIC plummeted 95.21 points, or 5.47 percent, to close unofficially at 1,645.12.

A year ago today, the Dow closed at a record high above 14,000. (Reporting by Leah Schnurr; Editing by Jan Paschal)