* Euro jumps, pushing dollar index to 8-1/2 month low * Traders cite Asian euro buying; U.S. QE worries hit dollar * Dollar trims earlier gains vs yen triggered by BOJ moves * Aussie slides after RBA surprises by not raising rates (Updates prices) By Jessica Mortimer LONDON, Oct 5 (Reuters) - The euro jumped against the dollar on Tuesday on reported Asian buying, pushing the greenback to an 8-1/2 month trade-weighted low, while the yen trimmed earlier falls against the U.S. currency. The yen fell after the Bank of Japan cut its key overnight rate target to 0-0.1 percent from 0.1 percent and said it would create a pool of funds to buy assets in the face of evidence yen strength was hurting Japan's economy. [ID:nTOE69305D] Analysts said the BOJ's moves were not sufficient to halt the downward trend in dollar/yen, however, with the U.S. currency pressured by falling U.S. bond yields and expectations the Federal Reserve will implement fresh quantitative easing. The yen's falls stalled just ahead of 84.00 yen per dollar, and it turned flat on the day in tandem with gains in euro/dollar, leaving intact expectations more Japanese intervention will be needed to curb yen gains versus the dollar. "The yen falls after the BOJ decision looked unlikely to last. When rates were so close to zero anyway a further rate cut will make very little difference," said Elsa Lignos, currency strategist at RBC. At 1108 GMT, the euro was up 0.7 percent at $1.3765, off a session high of $1.3794. Resistance was seen at $1.3809, a 6-1/2-month high, and traders cited options barriers at $1.3825. Traders reported Asian central bank buying of euros against the dollar, while a U.S. bank was also seen buying, driving it up sharply from below $1.3700. Asian central banks have been diversifying their currency reserves away from the dollar, particularly towards the euro. RBC's Lignos said the euro bounced above a trend support line, currently around $1.3650, which runs back to where the recent rally began in mid-September.

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