How Chemistry Can Help Predict Earthquakes Months Before the Earth Shakes

Earthquake warning systems, at this point, can only give "seconds to minutes of advance warning," once the Earth is already shaking. But a team of researchers may have found a way to see earthquakes coming months in advance. They discovered that before the ground shifts, the groundwater's chemistry does.

Working the geologically and seismically active hotspot of Iceland—a place that live-feeds volcanic eruptions—researchers from universities in Sweden, Iceland, and Saudi Arabia found that months before two moderate-class, magnitude-5 earthquakes hit in October 2012 and April 2013, respectively, the stress building up in the Earth's crust caused different types of groundwater to mix, which was evident in the chemical composition of the water. The results of the study appeared in the journal Nature Geoscience.

"In our study area we have the advantage that the deeper groundwater is very old (probably more than 10,000 years) which results in a very unique hydrogen isotope signature," Alasdair Skelton, the study's leader author, told me. "This makes mixing between deeper and shallower groundwater easy to detect. The concentrations of deuterium—which is the heavier isotope of hydrogen—and sodium increased before both earthquakes."

Smaller earthquakes that occurred during the study didn't have this chemical giveaway before the earthquake, although some had proof appear afterwards. It's worth noting, however, that a magnitude-5 earthquake, while noticeable, isn't usually very destructive. Why, just this morning, Iceland experienced a magnitude-4.9 temblor, and while it may have moved seismographs, it wasn't really big news for a country that experienced four magnitude-5 quakes in 48 shaky hours, back in August. As an instrument, watching the groundwater is probably as sensitive as it needs to be.

The frequency of earthquakes and distinctive age of the groundwater made Iceland an ideal place for the study, and while the results may not be transferable, the methods might be. It's just a matter of knowing the geological composition of an area, and knowing what to look for in the water.

"In other areas where groundwater is perhaps held within different rock types, we might expect other chemical differences related to the different types of rock, e.g. a limestone would provide more calcium whereas a sandstone would provide more silica to groundwater," Skelton said. "The concentrations of calcium and silica also increased [in the Iceland study] but the increases were too small to be reliably separable from background variation."

So there you go, California. When you're not watching the parched ground literally rise, you've got another reason to keep an eye on your wells beyond the fact that it's swiftly becoming the only water you've got left.