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Helium and argon, squeezed out of the earth through fissures by deep internal pressures, may signal an imminent earthquake. There has been little evidence, however, directly linking stress with gas emissions. Ryuichi Sugisaki of the earth sciences department at Nagoya University in Japan reports in the June 12 Science that the variations of the He/Ar ratio of gas bubbles in a mineral spring coincide with underground stresses caused by the earth tide.

‘A comparison of the variation of strain in the ground resulting from the earth tide with the observed fluctuation of the ratio shows a good correlation,’ Sugisaki wrote. In addition, he says that the ratio fluctuation is more closely tied to the tidal strain than to atmospheric pressure or temperature.