), for the purpose of predicting earthquakes, has been described as the Holy Grail of
seismology, i.e. highly desirable goal but with elusive results. Preseismic signals of the
order of 10–
20%, reported in the 1960ies and 1970ies, have not been convincingly reproduced. Lower level (0.5–
3.5%) coseismic and postseismic in situ changes have, however, repeatedly been reported. Due to lack
of seismicity
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