Eric Richardson [Flickr]

James Stewart competes during Moto X Best Whip at X Games 15, held at Staples Center in Downtown Los Angeles.

DOWNTOWN LOS ANGELES — Action got underway at ESPN X Games 15 on Thursday afternoon, with two of three events inside Staples Center belonging to the moto bikes.

In between, skateboarder Jake Brown returned to the scene of his nasty 48-foot fall two years ago to claim the gold medal in the Big Air Finals, unseating two-time defending champ Bob Burnquist.

The day kicked off with Moto X Best Whip, an event in which riders throw their bike sideways before pulling it back for a landing. Scoring was based on fan text messages, and Todd Potter took the win with 43% of voting.

The Skateboard Big Air took riders down the monster ramp that descends either 60 or 80 feet from Staples Center's upper seats, allowing them to cross either a 50- or 70-foot gap before going for height on the 27-foot quarter-pipe.

Finally, engines again revved as riders competed in Moto X Step Up, a two-wheeled high jump. After a short run-up, riders launch nearly vertically to reach the bar. Ricky Carmichael and Ronnie Renner shared a gold medal after both cleared 34 feet and failed to manage the 35-foot jump. Carmichael crashed on his last attempt, but walked away after being attended to by medical staff.