Task: Question Generation
Input (English): On April 20,2013, a big and powerful earthquake attacked Ya'an, Sichuan Province. A great many buildings and houses _ a lot of people were killed and even more people lost their homes in the earthquake . Death toll from the 7.0-magnitude earthquake that hit Ya'an in southwestern China's Sichuan Province has risen to 188 (as of 18:00 pm, April 22, ), according to latest calculations by local Civil Affairs Bureau. At least 11,826 were reportedly injured in the quake while 25 are still missing, the bureau said. Experts are anticipating much less casualties in the quake than that from the 8.0 magnitude quake hit Wenchuan on May 12, 2008, also in Sichuan Province, which killed more than 80,000 and injured over 300,000. Energy released from Wenchuan earthquake would be 30 times of that from Ya'an quake, according to Zhang Xiaonan, an expert with China's Geophysical Union. Dai Junwu with Harbin-based seismological bureau expects the death toll at less than 1,000, and economic losses from the quake could reach up to 100 billion yuan. Police and expert teams have already rushed for rescue in the quick stricken areas, and the State Council has banned unauthorized rescue efforts and individual vehicles from going to the quake zone to avoid congestion . Rescue efforts were carried "timely and orderly", said Chinese Premier Li Keqiang who flew to the quicken-stricken area on Sunday, the second day of the quake. He was quoted as saying that "the current priority is to save lives".
Output (English): When did Ya'an earthquake occur?