An earthquake, also known as a quake, tremor or temblor, is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.
At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity.
Two earthquakes kill at least 64 in Yunnan's Yiliang county
Death toll expected to rise with thousands of houses destroyed by rockslides in Yiliang county
At least 64 people were killed and 715 injured when two strong earthquakes rocked Yiliang county in Yunnan , southwest China, yesterday.
The death toll in the mountainous region is expected to climb, with thousands of houses crushed by rockslides that occurred after the quakes.
Premier Wen Jiabao is on his way to inspect the quake zone, which lies on the border of Yunnan and Guizhou .
The epicentre of the first quake, which struck at 11.19am with a magnitude of 5.7, was 15 kilometres from Yiliang's county centre. The second quake, which struck at 12.16pm with a magnitude of 5.6, was centred five kilometres away.
Yiliang, where most people live in a valley surrounded by high mountains, is about 400 kilometres from Kunming , the provincial capital.
Xinhua reported that about 700,000 people in Zhaotong's Yiliang county, Zhaoyang district and Daguan county as well as in 24 other rural townships were affected.
Tremors were felt in Chongqing and Sichuan's provincial capital, Chengdu .
More than 200,000 people had to evacuate the area as more than 20,000 houses collapsed.
Yiliang's county government announced that at least 63 people from the county had died there. Xinhua said at least one person was killed in Zhaoyang district.
At least two were injured in Guizhou's Weining county.
Yang Xingqin, 38, a peasant from Yiliang's Xiongkuai village, said she was glad that her family of six survived, but said three of the family's mud-brick houses had collapsed.
Yang said: "More than 300 square metres of housing was reduced to debris in a few minutes and five of my pigs were killed.
"I was very scared and I was crying. Everything was gone in a few minutes."
Yunnan's head of earthquake administration, Huang Pugang, told Xinhua that houses in the impoverished region were not built to resist quakes.
Yunnan's provincial government issued its highest emergency response alert and more than 5,600 public security officials, armed police and volunteers arrived in the quake zone to help with rescue efforts.
Additional reporting by Louise Ho