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.
Recent seismic activity in China no cause for concern
Authorities have dismissed fears that a series of minor earthquakes, which struck China last week, were a sign of a major, destructive one yet to come, Oriental Morning Post reported.
Between February 18 and 22, a total of 10 earthquakes, all magnitude 4 or greater, struck China, according to China Earthquake Network Centre. Eight of the earthquakes occurred in Sichuan province on February 19.
A 4.8-magnitude quake that hit Guangdong province on Friday was felt in Hong Kong.
Although no deaths have been reported, the unusually high number of earthquakes within a short period of time has sparked public concern that a larger earthquake will follow.
But professor Wan Tianfeng of the China University of Geosciences said the recent earthquakes, which were all below magnitude 6 and not destructive, constituted normal seismic activity.
“All of these quakes took place at known seismic areas where quakes had occurred before,” he said and appealed to the public not to panic.
Jiang Haikun, deputy director of China Earthquake Network Centre, said that the recent spate of seismic activity was rare but there was no need for concern.
“Based on previous earthquake history, mid-level earthquakes do not tend to trigger major earthquakes,” he said.
Several of the world’s deadliest earthquakes have occurred in China. In 1976, an earthquake that struck Tangshan in Hebei province claimed 240,000 lives and injured 160,000. In 2008, a magnitude 8 earthquake hit Wenchuan county in Sichuan province, killing more than 68,000.