TOKYO (AP) — Karsten Warholm of Norway obliterated his own world record in the Olympic 400-meter hurdles Tuesday, finishing in 45.94 to crack the old mark by .76. One of the most anticipated races on the program more than lived up to the hype. Second-place finisher Rai Benjamin of the United States finished in 46.17, a mark that also beat the record Warholm set last month. This time, it was good for only second. Warholm flashed that trademark look of amazement when he crossed the line first. Alison dos Santos of Brazil finished third and six of the eight runners broke either a world, continental or national record.