In addition to massive temblors, plenty of human activities can trigger tiny ground motions, and for more than a quarter century scientists have been trying to figure out whether geothermal power generation
(above, pipes carry steam in Iceland) could be a culprit.
In January 2007, European newspapers reported outrage in Basel, Switzerland, after residents learned that a series of more than 60 earthquakes--reaching magnitudes as high as 3.4--may have been triggered by geothermal plants.
This form of power generation could affect earthquakes in two ways, a research team reported in 1982 in the journal Geophysical Research Letters.
For one, harnessing geothermal energy can require injections of water deep into the hot Earth to create steam, which is then carried to a generation plant by pipes. Such injections might add pressure to any geologic faults surrounding the area where water is injected.
Geothermal power can also come from hot water pumped out of the rocks, but this removes the faults' lubrication. The sides of a fault can then get stuck, allowing pressure to build and suddenly release.
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Photograph by Jonas Bendiksen/NGS