A team of geologists from Iceland, Sweden and Saudi Arabia has found changes in groundwater chemicals prior to earthquakes. They emphasize that they haven’t found a precursor to earthquakes, but there seems to be a connection between these chemical changes and incoming earthquakes.
Húsavík, Iceland. Image source.
There is no reliable earthquake warning system, and there almost certainly won’t be any (at least in the near future). The immense complexity of the systems involved in earthquakes makes it borderline impossible to generate reliable predictions. But scientists are still trying to find a way to predict earthquakes, and this is as good of an idea as any. Researchers now want to conduct the same type of tests around the world and see if they get similar results. If they do, then they will know this is a universal mechanism which does in fact hold promise.
For several decades, scientists have suspected that ground water experiences changes prior to an earthquake. The first such study was made in China, in 1976, and another, more thorough one was conducted after the Kobe quake in 1995. However, both these study suffered from the same problem – the lack of data. Both of them analyzed a single event, and you can’t really draw a general conclusion based on one earthquake.
In this study, geologists took a more systematic approach, analyzing groundwater samples every week for the five year period 2008-2013 from an artesian well in the town of Húsavík, a place with a history of earthquakes. They found that six months prior to a 5.6 magnitude earthquake in 2012 and again just prior to another 5.5 magnitude earthquake in 2013, hydrogen and sodium levels in the water increased a significant level. Because the study was conducted over a longer period of time, we’re not dealing with a random change or a background variation. Furthermore, since this happened two times, it makes it less likely that this was a freak event, and more likely a pattern.
The researchers don’t offer any clear mechanism to explain these changes, but it’s likely something to do with the changes in strength.
“Statistical analyses indicate that the changes in groundwater chemistry were associated with the earthquakes. We suggest that the changes were caused by crustal dilation associated with stress build-up before each earthquake, which caused different groundwater components to mix. Although the changes we detect are specific for the site in Iceland, we infer that similar processes may be active elsewhere, and that groundwater chemistry is a promising target for future studies on the predictability of earthquakes”, researchers write.
Journal Reference: Alasdair Skelton,Margareta Andrén,Hrefna Kristmannsdóttir,Gabrielle Stockmann,Carl-Magnus Mörth,Árny Sveinbjörnsdóttir,Sigurjón Jónsson,Erik Sturkell,Helga Rakel Guðrúnardóttir,Hreinn Hjartarson,Heike Siegmund& Ingrid Kockum. Changes in groundwater chemistry before two consecutive earthquakes in Iceland. Nature Geoscience (2014) doi:10.1038/ngeo2250
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