* Vettel wins Korean Grand Prix for third consecutive year
* German can take fourth title in Japan next weekend
* Alonso a distant sixth (Adds details, quotes)
By Alan Baldwin
YEONGAM, South Korea, Oct 6 (Reuters) - Red Bull's Sebastian Vettel completed a hat-trick of Korean Grand Prix victories on Sunday to put himself only one week away from potentially clinching his fourth successive Formula One title.
The 26-year-old's third successive Korean win, and eighth triumph in 14 races, left him 77 points clear of Ferrari's Fernando Alonso with five races - and a maximum 125 points -remaining.
If the German wins in Japan next weekend - as he did last year - and Alonso fails to finish in the top eight - as also happened last year - the championship will be over.
"That was a very, very disciplined drive. Well done," team principal Christian Horner told him over the radio after taking the chequered flag. Vettel, who now has 34 career wins, replied with his customary whoop of delight.
Alonso could manage only sixth place on an overcast afternoon that threatened rain without delivering the downpours that might have mixed up the field and given him more of a hope. The Spaniard now has 195 points to Vettel's 272.
"There's still a chance for Fernando, I think," said Vettel. "So we have to stay on top of our game. But to be honest...we're just having a good time.
"I look forward to Japan because it's one of the nicest tracks of the whole season."
In a race that exploded into action, with two safety car periods including one bizarre moment when a fire marshals' regular 4X4 drove on to the track and led the field before the official Mercedes pace car had been deployed, Vettel celebrated his fourth victory in a row.
Finland's Kimi Raikkonen finished second, ahead of Lotus team mate Romain Grosjean, in a race running along familiar lines of Vettel domination before jolting the audience awake with a bang.
McLaren's Mexican Sergio Perez brought out the first safety car with the explosive delamination of his front right tyre, which had worn through after hard braking, that left a strip of tread lying in the middle of the track on lap 31 of 55.
When that safety car came in on lap 36, after the debris had been cleared, Vettel's Australian team mate Mark Webber was hit by Adrian Sutil's skidding Force India at the re-start.
The Australian pulled over with his car on fire, for the second race in a row.
With marshals struggling to put out the blaze with extinguishers, the 4x4 appeared on the track ahead of the field between turns one and two and with its hazard lights on while the official Mercedes SLS AMG safety car brought up the rear.
"It's not great getting stuck behind the safety car but I'm really pleased with the result and great by the team," said Vettel, whose podium appearance at the sparsely-attended Yeongam circuit met none of the booing that had marked the previous three races.
"Fortunately we had enough pace to get ahead after both safety cars but both Kimi and Romain were very competitive and did better with their tyres," he added.
Vettel had made a clean start from pole, his third in a row, while Mercedes' Lewis Hamilton - who ended up fifth at the finish - dropped to third when Grosjean passed him.
Germany's Nico Hulkenberg, whose reputation was burnished further with what he said had been one of the best races of his career, drove to fourth place for Sauber after starting in seventh place and overtaking Alonso.
The Spaniard skilfully avoided tangling with his Ferrari team mate Felipe Massa, who spun in the opening seconds and dropped to last.
Massa recovered to ninth place, behind Mercedes' Nico Rosberg - who paid the price for a long pit stop to replace a front wing that had been hitting the ground and sending up showers of sparks - in seventh place and Jenson Button eighth for McLaren. Perez took the final point.
Britain's Paul Di Resta was the first retirement, his sixth race without a point, when he spun his Force India and hit the barriers after 26 laps.
Raikkonen, who will be Alonso's team mate at Ferrari next year, passed Grosjean on lap 38 moments before the second safety car period.
The Pirelli tyres, much criticised earlier in the season following a spate of blowouts, again triggered a chorus of dissent after a race dictated by high levels of degradation.
"The tyres are wearing a lot and they also explode a bit - but that is for Pirelli to sort out," commented Webber.
"Pirelli will put the puncture of Perez down to a lock-up but the reason the drivers are locking up is because there's no tread left." (Reporting by Alan Baldwin, editing by Amlan Chakraborty)