The research team of Associate Professor Takahiro Hosono of Kumamoto University conducted a joint research with California University Berkeley and Kansai Gakuin University. Was increased, and it was found that this was due to the supply of new water to the lower stream.
Changes in the so-called hydrological environment (environment where water circulates), such as the withering of water in ponds and wells due to the occurrence of an earthquake, the sudden occurrence of running water, or the rise in water level, dates back to the Roman era, and many of the world's so far. Has been described in the area of.Even after the Kumamoto earthquake, an abnormal rise in the groundwater level of up to about 10 m was confirmed, mainly in the recharge area of the wide-area groundwater flow system.Various conditions are required to elucidate such abnormal changes, but in the area around Kumamoto City, almost 100% of the drinking water source is covered by groundwater, there are many observation wells, and various data such as water level and water quality are available. I was able to grasp the changes in the hydrological environment due to the earthquake in detail.
This time, we analyzed the stable isotope ratios of various water samples collected before and after the Kumamoto earthquake.The stable isotope ratio of water on the surface of the earth changes only slightly through various processes that occur on the earth such as evaporation and condensation, but it can be used as a marker to estimate the origin of water because it takes a unique value depending on the location. ..As a result of the analysis, it was found that the cause of the abnormal rise in water level was that the seismic activity increased the permeability of the Aso west foot aquifer and supplied new water originating from the mountain body to the lower stream.
Many unclear points remained about the causes and processes of water level rise and water volume increase due to the occurrence of a huge earthquake, but this study revealed detailed changes in the hydrological environment.In addition, this result is important from the viewpoint of conservation and governance of water resources in the Kumamoto area, which uses groundwater as a drinking water source.
Paper information:[Nature Communications] Stable isotopes show that earthquakes enhance permeability and release water from mountains
