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Groundwater oxygen isotope anomaly before the M6.6 Tottori earthquake in Southwest Japan.


ABSTRACT: Geochemical monitoring of groundwater in seismically-active regions has been carried out since 1970s. Precursors were well documented, but often criticized for anecdotal or fragmentary signals, and for lacking a clear physico-chemical explanation for these anomalies. Here we report - as potential seismic precursor - oxygen isotopic ratio anomalies of +0.24‰ relative to the local background measured in groundwater, a few months before the Tottori earthquake (M 6.6) in Southwest Japan. Samples were deep groundwater located 5?km west of the epicenter, packed in bottles and distributed as drinking water between September 2015 and July 2017, a time frame which covers the pre- and post-event. Small but substantial increase of 0.07‰ was observed soon after the earthquake. Laboratory crushing experiments of aquifer rock aimed to simulating rock deformation under strain and tensile stresses were carried out. Measured helium degassing from the rock and 18O-shift suggest that the co-seismic oxygen anomalies are directly related to volumetric strain changes. The findings provide a plausible physico-chemical basis to explain geochemical anomalies in water and may be useful in future earthquake prediction research.

SUBMITTER: Onda S 

PROVIDER: S-EPMC5859118 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Groundwater oxygen isotope anomaly before the M6.6 Tottori earthquake in Southwest Japan.

Onda Satoki S   Sano Yuji Y   Takahata Naoto N   Kagoshima Takanori T   Miyajima Toshihiro T   Shibata Tomo T   Pinti Daniele L DL   Lan Tefang T   Kim Nak Kyu NK   Kusakabe Minoru M   Nishio Yoshiro Y  

Scientific reports 20180319 1


Geochemical monitoring of groundwater in seismically-active regions has been carried out since 1970s. Precursors were well documented, but often criticized for anecdotal or fragmentary signals, and for lacking a clear physico-chemical explanation for these anomalies. Here we report - as potential seismic precursor - oxygen isotopic ratio anomalies of +0.24‰ relative to the local background measured in groundwater, a few months before the Tottori earthquake (M 6.6) in Southwest Japan. Samples wer  ...[more]

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