Effect cause, this is.
PTI : London, Sun Dec 15 2013
Some of the world’s largest and most deadly recent earthquakes were not natural disasters at all but were caused by human activities such as mining, reservoir construction and oil and gas extraction, scientists say.
A global study of hundreds of quakes by Christian Klose, a consultant geophysicist, identified 92 large earthquakes likely to have been caused by humans.
Klose said that the Erth’s crust is littered with geological faults under enormous tensions similar to those in a coiled spring.
When humans pile up vast masses of water or minerals on the surface, or extract them from beneath, the change in the weight of the overlying land can be enough to release that geological tension, causing an earthquake.
“The data specifically shows that human-made mass changes can advance the clock of natural seismic cycles and induce or trigger new earthquakes,” said Klose.
According to the research, the 2008 earthquake in Sichuan, China, which had a magnitude of 7.9 and killed 80,000 people, was triggered by the construction of the Zipingu reservoir.
In Britain, the 2007 Folkestone earthquake, which rocked southeast England and measured 4.3, was triggered by the millions of tonnes of shingle piled up to protect Folkestone harbour, ‘The Times’ reported.
The study said the 2011 earthquake in Lorca, southeast Spain was apparently triggered by water being extracted from underground reservoirs.
Another, with a magnitude of 5.6, hit Newcastle, Australia, in 1989; 13 people died and hundreds were injured. Klose linked this with the amount of coal extracted from nearby mines.
The research is published in the Journal of Seismology.