There have been relatively few reported observations of temperature
changes in the earth prior to earthquakes. This is probably due to
a lack of experiments to look for such an effect. The thermal
measurements taken at hot springs in volcanic areas. Most of the
observations were taken within 50 km of the epicenters of the coming
earthquakes, although the greatest reported epicentral distance for an
anomaly was 470 km. In all cases an increase in ground temperature
was reported, with the largest change being 6 °C and most of the
changes being b1 °C. Five of the temperature changes in groundwater
were reported to have been coseismic, i.e., having occurred at the time
of the earthquake, while 5 were reported to take place within the
10 days prior to the earthquake. The rest of the observations did not
report the time at which the temperature change was reported.
All of these reported changes in temperature associated wi