Funding for this research was provided by:
Japan Society for the Promotion of Science (17K01322)
Text and Data Mining valid from 2019-07-09
Received: 22 March 2019
Accepted: 4 June 2019
First Online: 9 July 2019
: BLNK is Emeritus Professor of Seismology, The Australian National University. TF is a Professor at the Earthquake Research Institute, The University of Tokyo.
: The authors declare that they have no competing interests.
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