* Dollar/yen hits 15-yr low below 83 yen
* Euro/dollar soars through resistance to 1-month high
* Dollar falls below parity vs Swiss franc (Updates prices)
NEW YORK, Sept 14 (Reuters) - The U.S. dollar fell across the board on Tuesday, touching a 15-year low below 83 yen as a break of technical support levels in several currency pairs sparked a stampede out of the greenback.
With concerns growing about intervention by Japanese authorities to weaken the yen, the currency got a particular boost after Japan's prime minister won a leadership vote. Prime Minister Naoto Kan won an unexpectedly decisive victory over party heavyweight Ichiro Ozawa, who had been more strident in his calls to intervene to weaken the yen.
"A string of stories that suggest the (U.S. Federal Reserve) is closer to QE2 than the market might appreciate offers by far the best explanation for the price action in the last 24 hours, including: higher gold, broad-based USD weakness, rallying Treasuries, curve flatteners and modest positive risk trades," said Alan Ruskin, global head for G10 FX at Deutsche Bank in New York.
A rally by the euro to a one-month peak against the dollar also grabbed traders' attention after it broke out of its range of recent weeks to the upside amid market talk about possible further quantitative easing in a bid to stimulate the U.S. economy.
"It seems people are vacating dollar positions today and that money is shifting into other safe-haven assets for the time being," said Greg Salvaggio, vice president of trading at Tempus Consulting in Washington, citing the yen, the Swiss franc and gold.
But Salvaggio said he would be selling euros anywhere near $1.30 and buying dollar-yen below 83 in the belief the U.S. economy is beginning to turn the corner.
The euro's advance began after U.S. retail sales rose more than expected in August, notching the largest gain in five months.
Once the euro broke above the $1.2920 to 30 area, a level that had held since August, it kept going to a one-month high of $1.3033. It was last up 1 percent at 1.3007.
The significant break came in late morning New York trade on market talk that Goldman Sachs said in a research note that while it suspects the Federal Reserve will ratchet down growth forecasts, the revision is unlikely to be enough to spark additional easing.
The Wall Street Journal quoted Goldman Sachs chief U.S. economist Jan Hatzius on Tuesday reiterating the bank's view on quantitative easing.
The euro was up 0.3 percent at 108.07 yen.
The Goldman note talk also pushed the dollar index, a non-traded calculation that measures the dollar's performance against six currencies, below the 200-day simple moving average for the second straight day, according to Reuters data.
The index is now oversold for the first time since Aug. 6 based on the 14-day relative strength index.
Amid broad U.S. dollar woes, the Australian dollar surged to its highest against its U.S. counterpart since mid-2008 after breaching an important technical level. It was last at $0.941, up 0.7 percent from late Monday. The move accelerated after the currency broke above a recent high around $0.9365.
YEN BREAK
The dollar fell to a 15-year low of 82.92 on electronic trading platform EBS and 82.93 on Reuters. It last traded at 83.10, down 0.7 percent on the day.
The yen has gained more than 10 percent against the dollar this year as recent weak U.S. data and record-low bond yields drove money away from U.S. assets. Japan worries that a strong yen will hurt its export-driven economy.
The Kan victory provided "positive yen news," said Joseph Trevisani, chief analyst at FX Solutions in Saddle River, New Jersey. But he added that "83 has no more meaning than the typical round number in dollar/yen. The level to look at is the all-time low."
That low is at 79.75 yen.
Tempus' Savalggio suggested that Japanese intervention below 83 yen is a real risk and suggested going short yen. Traders also cited "stop-loss" orders around 82.85 yen. If the dollar hits 82 yen in a couple of hours, the risk of intervention would rise, analysts say.
Dollar/yen three-month composite risk reversal was at -2.15 on Tuesday from -1.9 on Monday, with a bias to dollar puts and yen calls and indicating slightly more bullishness on the yen.
Boris Schlossberg, head of research at GFT Forex, said traders would try to push the dollar toward the all-time low beneath 80 yen, though he said if U.S. economic data starts to improve, short dollar positions could be in for a squeeze.
Lingering doubts about the longer-term global outlook kept the safe-haven Swiss franc in demand. The dollar fell to 0.9934 francs, the lowest since late November 2009.