Sharapova, the defending tournament champion, struggled with her serve at times against the third-seeded Kerber but prevailed 6-3, 2-6, 7-5.
Sharapova will face China's Li Na, the No. 2 seed who topped American qualifier Bethany Mattek-Sands 6-4, 6-3. Li served three aces and won 68 percent of her first-service points.
Biologists detail four new deep-sea 'killer sponges'
Pistorius testifies he didn't consciously pull trigger when he shot girlfriend