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.
Quake survivors in Yunnan, China, fear aftershocks as rescuers search last parts of quake zone
Hundreds of survivors fear fresh aftershocks even as rescuers search the last isolated parts of disaster zone
Thousands of military and civilian rescuers continued an arduous search yesterday for survivors of two relatively mild earthquakes that killed dozens of people in Yunnan on Friday, as many citizens lived in fear of further quakes.
More than 7,200 soldiers from the People's Liberation Army and paramilitary were mobilised and sent to the quake zone in Yiliang county, Zhaotong , where the magnitudes 5.7 and 5.6 quakes struck at around 11am and noon, respectively, Xinhua reported.
The death toll increased by about 20 yesterday as rescuers reached cut-off villages and found more bodies. The confirmed toll reached 81 by the afternoon. More than 800 people were injured, 200,000 lost their homes and an unknown number were missing.
After two days, more than 90 per cent of the quake zone had been searched, and rescuers were eyeing the final isolated areas yesterday, according to China National Radio.
Landslides triggered by the quakes cut off access to many towns and villages, and rescue efforts were slowed by collapsed roads and bridges, as well as by rocks that continued falling from mountains. The latest setback involved the collapse of a key road shortly after 3pm yesterday. The road spanned from downtown Yiliang to one of the worst-hit areas, Luozehe town.
Premier Wen Jiabao flew to the area on Friday within hours of the disaster. While on the plane, he was quoted by Xinhua as saying he was confident the people would be able to overcome the tragedy, and he pointed to the recovery following the devastating Sichuan earthquake in 2008 that killed more than 87,000 people.
But not all of the survivors shared his optimism so soon after Friday's quakes. Some said the government was not doing enough.
A doctor at the People's Hospital in Yiliang said yesterday that they were short of help and medical supplies to treat thousands of injured people.
Most of the victims were farmers and their families, who were killed or injured when their homes collapsed, said the doctor, declining to be named. Others were hit by falling objects.
"We are a remote county with a very low level of economic development," he said. "I don't think the government fully understands the difficulties here.
"They have not sent us enough doctors or medicine to treat the critically injured. It's been two days, but many patients are still left out in the open because we ran out of beds."
The owner of a restaurant near the county government headquarters said the people still did not feel safe. His restaurant was helping to feed hundreds of PLA soldiers.
"When there's an aftershock, the officials and soldiers jump as we do, and they can't tell us whether there will be another big quake in the coming days," the owner said. "Most people have left their homes and are sleeping in the open at night because nobody believes the government will give us warning when the next big jolt comes."
Earthquake predictions are difficult even with the most advanced technology.
The unusually high death toll for quakes below magnitude 6 has prompted criticism online about poor building quality in the area. Some people online have cited stronger quakes with lower death tolls in other countries.
Huang Fugang , director at the Yunnan Seismological Bureau, conceded to Xinhua on Saturday that poor building quality was one of the reasons for the high death toll.
Huang said most farmers in Yiliang lived in houses that were not strong enough to withstand quakes, simply because sturdier materials were too expensive.