Thousands of rescuers fought altitude sickness, chilly weather, strong winds and frequent aftershocks Thursday to dig through rubble and reach survivors of a strong earthquake that has left 760 dead in northwest China.

The 7.1-magnitude quake, which struck the Tibetan Autonomous Prefecture of Yushu in southern Qinghai Province early on Wednesday, also toppled 15,000 residential buildings and forced 100,000 residents to be relocated, according to the rescue headquarters.