DisastersHuman activity can trigger an earthquake

Published 30 October 2012

Earthquakes occur when tectonic plates try to move past each other, and the friction between them holds them in place; the friction creates energy which builds up, and when the plates move past each other, the energy is released, triggering an earthquake; fracturing increases the fluid pressure inside faults; this increased pressure, in turn, lowers the stress threshold for triggering an earthquake enough for one to take place

Scientists are beginning to wonder whether human activity could play a role in the occurrence of an earthquake.

Earthquakes occur when tectonic plates try to move past each other, and the friction between them holds them in place. The friction creates energy which builds up, and when the plates move past each other, the energy is released, triggering an earthquake.

Arstechinca reports that usually, humans cannot affect the way tectonic plates move or the energy this movement creates, but recently scientists realized hydraulic fracturing could play a role in the creation of an earthquake.

Hydraulic fracturing is a method in which fluids are pumped into the ground at an extremely high pressure to crack rocks, and release natural gas and oil stored in the rocks. Scientists have determined that fracturing increases the fluid pressure inside faults. This increased pressure, in turn, lowers the stress threshold for triggering an earthquake enough for one to take place.

When an earthquake struck Lorca, Spain on 11 May 2012, researchers and scientists wasted no time in testing to see whether it was caused by fracturing. Satellites recorded changes in elevation near the fault and with seismometers, scientists were able to locate where the fault slipped and by how much.

Scientists then used computer models to determine the effects of groundwater depletion on the area. The model showed the depletion altered the stresses along the fault in the exact spot were the earthquake occurred. 

This could be a one-time coincidence, but scientists and seismologists think they are connected.

The earthquake was not a significant one, registering a 5.1 magnitude, which is considered moderate on the Richter scale. It was, however, the strongest earthquake to hit the region since 1956, which killed nine people.

Scientists in the field are aware that an earthquake can strike in this region without the effects of groundwater depletion and fracturing, but this earthquake seems to be directly related to human activities. This has the potential to be a sensitive subject in the future, as fracturing is on the rise. In the future, before fracturing is allowed in an area, scientists may have to determine whether the area is safe from seismic activity, something that will not be easy to do.

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