Effects of the Japanese 2016 kumamoto earthquake on nitrate content in groundwater supply

Kei Nakagawa, Jun Shimada, Zhi Qiang Yu, Kiyoshi Ide, Ronny Berndtsson

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


The 2016 Kumamoto earthquake had a significant impact on groundwater levels and quality. In some areas, the groundwater level increased significantly due to the release of groundwater from upstream mountainous regions. Conversely, the groundwater level in other areas greatly decreased due to the creation of new fracture networks by the earthquake. There were also significant changes in certain groundwater quality variables. In this study, we used clustering based SOM (self-organizing maps) analysis to improve the understanding of earthquake effects on groundwater quality. We were especially interested in effects on groundwater used for drinking purposes and in nitrate concentration. For this purpose, we studied groundwater nitrate (NO3 + NO2–N) concentrations for the period 2012–2017. Nitrate concentration changes were classified into seven typical SOM clusters. The clusters were distributed in three representative geographical regions: A high concentration region (>4 mg/L), a low concentration region (<1.6 mg/L) with minimal anthropogenic loading area, and an intermediate concentration region (2–4 mg/L). Depending on these regions, the nitrate concentration changes just before and after the earthquake had both increasing and decreasing trends between 2015–2017. This points to complex physiographical relationships for release of stored upstream groundwater, promotion of infiltration of shallow soil water/groundwater, and nitrate concentration as affected by earthquakes. We present an analysis of these complex relationships and a discussion of causes of nitrate concentration changes due to earthquakes.

Original languageEnglish
Article number43
Pages (from-to)1-17
Number of pages17
Issue number1
Publication statusPublished - 2021 Jan


  • 2016 Kumamoto earthquake
  • Groundwater
  • Nitrate
  • Self-organizing maps

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology


Dive into the research topics of 'Effects of the Japanese 2016 kumamoto earthquake on nitrate content in groundwater supply'. Together they form a unique fingerprint.

Cite this