Atmosphere and Ocean Research Institute, The University of Tokyo.
Institute of Surface-Earth System Science, Tianjin University.
Proc Jpn Acad Ser B Phys Biol Sci. 2020;96(7):322-334. doi: 10.2183/pjab.96.024.
Here, we report the groundwater oxygen isotope anomalies caused by the 2016 Kumamoto earthquake (M7.3) 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 δO 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 δO enrichment via oxygen isotopic exchange between rock and porewater without changing δH.
在这里，我们报告了 2016 年 4 月 16 日发生在日本西南部熊本县的 2016 年熊本地震（M7.3）引起的地下水氧同位素异常。我们从熊本县三帆市震中东南 3 公里处的一口深井中采集了 117 个地下水样本；这些样本是装在 PET 瓶中的饮用水，分布在 2015 年 4 月至 2018 年 3 月之间的区域。此外，我们通过腔衰荡光谱法评估了氧和氢同位素，而无需进行任何预处理。地震发生后不久，δO 值（高达 0.51‰）就出现了异常增加，并且在地震前 2016 年 1 月就出现了 0.38‰的前兆性增加。在这些期间，氢同位素比值没有明显变化。与地震相关的快速地壳变形可能增强了含水层岩石的微破裂和新表面的产生，通过岩石与孔隙水之间的氧同位素交换导致 δO 富集，而不改变 δH。
