Earthquakes can be catastrophic natural disasters. But now we know that some earthquakes aren't natural. Human beings can actually cause them. 

That's the case with an earthquake in Lorca, Spain, last May. The quake measured 5.1 on the Richter scale and killed nine people. According to an analysis published in Nature Geoscience, the Lorca quake was caused by the extraction of groundwater from an aquifer near the fault that slipped. (Scientific American is part of Nature Publishing Group.)

In fact, it doesn't take much to trigger an earthquake. Oil and gas wells, rock quarries, even the added pressure of a reservoir lake behind a new dam can cause the ground to rumble. But we don't know what pressure levels are safe, nor is it clear whether man-made quakes are unique or just the early arrival of temblors that would have occurred naturally.

In the Lorca quake, the shaking itself was much stronger than might be expected from the removed water pressure. Which means we may be able to start earthquakes but we can’t predict their size. If we could, we might be able to relieve stress on schedule and without loss of property—or life.

—David Biello

[The above text is a transcript of this podcast.]