Although we believe that precursory signs of an
earthquake can occur before the event, it is difficult
to observe such evidence with precision. This is especially
the case when observations are made on the earth’s
surface, where the precursory signals of earthquakes
can be disturbed by artificial noise and other factors. One
possible solution to this problem is to make observations
with meters installed in the deep bedrock where
earthquakes occur.
If continuous observational data can be obtained for
stress, we gain access to new information that previously
could not be obtained for studying earthquake
occurrence and mechanisms and further advances in
earthquake research can be expected. However, no
instrument capable of continuous observations of stress
had been developed. We therefore developed a new