HUALIEN, Taiwan — Rescuers in Taiwan searched badly damaged buildings Thursday looking for scores of people missing after a powerful earthquake hit the island’s east coast. The magnitude-6.4 quake struck at 11:50 p.m. Tuesday and was centered 14 miles northeast of the coastal city of Hualien. The shaking was felt across Taiwan, but in Hualien the force was disastrous, collapsing walls and leaving buildings resting at alarming angles. On Wednesday a clearer toll emerged: seven dead, ranging in age from 37 to 66, and 67 others missing, officials said.