Groundwater helium level could signal potential risk of earthquake

A relationship between helium levels in groundwater and the amount of stress exerted on inner rock layers of the earth, found at locations near the epicenter of the 2016 Kumamoto earthquake, has now been revealed by researchers. The scientists hope the finding will lead to the development of a monitoring system that catches stress changes that could foreshadow a big earthquake.
Geology News — ScienceDaily