EARTHQUAKES in Italy鈥檚 Apennine mountains may be caused by an unusual mechanism. Giovanni Chiodini and his colleagues from the National Institute of Geophysics in Naples say the culprit is the build-up of carbon dioxide gas underground and that it may be possible to spot at-risk areas in advance.
The scientists measured CO2 levels in water samples from 139 springs situated in and around a region of the Apennines stretching from Florence to just south of Salerno. Superimposing a map of CO2 levels onto a map of seismic activity revealed a surprising trend: the more seismically active an area, the lower the levels of CO2 in its water. Chiodini鈥檚 team suspect that seismically active areas contain more underground crannies where the gas can become trapped. In non-seismic areas the gas tends to make its way to the surface unhindered and dissolves in groundwater.
The Apennines suffer from frequent small tremors and the occasional larger judder such as the Umbrian quake of November 1997, which measured 6 on the Richter scale. It partially destroyed an artistic treasurehouse, the basilica of San Francesco in Assisi, and killed 11 people.
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These earthquakes may be triggered by high CO2 pressures and, as Chiodini suggests, monitoring underground levels of the gas could help determine areas that are most at risk.