Note 136 — Chapter XVI

The only other explanation that seems to have any standing is the psychological hypothesis of Montessus de Ballore as given in Les Tremblements de Terre. He attributes the apparent seasonal variation in earthquakes to the fact that in winter people are within doors, and hence notice movements of the earth much more than in summer when they are out of doors. There is a similar difference between people's habits in high latitudes and low. Undoubtedly this does have a marked effect upon the degree to which minor earthquake shocks are noticed. Nevertheless, de Ballore's contention, as well as any other psychological explanation, is completely upset by two facts: First, instrumental records show the same seasonal distribution as do records based on direct observation, and instruments certainly are not influenced by the seasons. Second, in some places, notably China, as Drake has shown, the summer rather than the winter is very decidedly the time when earthquakes are most frequent.