By Kiyoshi Takenaka and Sakura Murakami NANAO, Japan (Reuters) -Rescue teams in Japan on Tuesday struggled to reach isolated areas hit by a powerful earthquake on New Year’s Day, with reports of more than 20 people dead in a disaster that toppled buildings and knocked out power to tens of thousands of homes. The quake with a preliminary magnitude of 7.6 struck in the middle of the afternoon on Monday, prompting residents in some coastal areas to flee to higher ground as tsunami waves hit Japan’s west coast, sweeping some cars and houses into the sea. Thousands of army personnel, firefighters a…