Here, we report the groundwater oxygen isotope anomalies caused by the 2016 Kumamoto earthquake (M_JMA7.3) that occurred in Southwest Japan on April 16, 2016. One hundred and seventeen groundwater samples were collected from a deep well located 3 km to the southeast of the epicenter in Mifune Town, Kumamoto Prefecture; they were drinking water packed in PET bottles and distributed in the area between April 2015 and March 2018. Further, the oxygen and hydrogen isotopes were evaluated via cavity ring-down spectroscopy without performing any pretreatment. An anomalous increase was observed with respect to the δ¹⁸O value (up to 0.51‰) soon after the earthquake along with a precursory increase of 0.38‰ in January 2016 before the earthquake. During these periods, there was no noticeable change in the hydrogen isotopic ratios. Rapid crustal deformation related to the earthquake may have enhanced the microfracturing of the aquifer rocks and the production of new surfaces, inducing δ¹⁸O enrichment via oxygen isotopic exchange between rock and porewater without changing δ²H.

在这里，我们报告了2016年4月16日在日本西南部发生的2016年熊本地震（M _JMA 7.3）引起的地下水氧同位素异常。从位于日本东南部3公里处的一口深井中收集了一百一十七个地下水样品熊本县御船町的震中；他们将饮用水装在PET瓶中，并于2015年4月至2018年3月在该地区分配。此外，无需进行任何预处理，即可通过腔衰荡光谱法评估氧和氢同位素。被相对于观察到对δ中的异常增加¹⁸地震发生后不久的O值（高达0.51‰）以及地震发生前的2016年1月先兆增加了0.38‰。在这些时期中，氢同位素比率没有明显变化。与地震相关的快速地壳形变可以具有增强的含水层岩石的微裂缝和生产新的表面，诱导δ ¹⁸ Ø富集不改变δ岩石孔隙水和通过之间的氧同位素交换² H.