Defending champion Ryder Hesjedal of Victoria moved into third in the overall classification after finishing 10th in Friday's stage.
It was a difficult day for Tour de France champion Bradley Wiggins, who had trouble negotiating the slippery roads on a technical descent shortly before the finish. He fell at one point but did not appear to suffer a major injury. Still, he appeared unnerved and lost more than a minute to the other contenders.
Hansen, who rides for the Lotto Belisol team, clocked more than 4 1/2 hours over the 176-kilometre leg from San Salvo to Pescara.
Enrico Battaglin of Italy finished second, one minute seven seconds behind, and 2007 Giro winner Danilo Di Luca of Italy was third with the same time.
Intxausti, who rides for the Movistar team, took a five-second lead over top contender Vincenzo Nibali of Italy, with Hesjedal eight seconds back in third.
Wiggins is 1:32 behind, although he could make up a big chunk of time in stage 8 on Saturday, a 55-kilometre individual time trial from Gabicce Mare to Saltara where he'll be the top favourite.
Hansen broke away from the main pack with other riders just 30 kilometres into the stage then attacked his last breakaway companion, Emanuele Sella of Italy, with 20 kilometres to go.
"Our team tactics were to get in a breakaway and today was the day we thought best to be in the break," Hansen said. "This is the biggest win of my life."
Sella also fell twice, and Nibali slid nearly 10 metres across the road during a downhill attack. He also appeared to avoid serious injury.
Many other riders also fell.
"I wanted to earn some time before tomorrow's time trial," Nibali said. "It would have been better without the fall."
The race ends May 26 in Brescia.