Note on the Effect of Atmospheric Pressure as Impulsive Agent of Earthquakes and Volcanoes

Abstract

It is generally accepted that one of the secondary causes of earthquakes and volcanic eruption is the variation of atmospheric pressure. The author of the present paper thought that a certain tectonic line or volcano has a special mode of dislocation or eruption, and consequently it is necessary to take a special condition of atmospheric pressure gradient proper to them when a fault or an eruption occurs there. In this paper this working hypothesis is accertained using seismometrical and volcanic data of semidestructive earthquakes and strong eruptions observed at our meteorological stations. The following conclusions are drawn:-
(1) Dislocation may occur when the direction of atmospheric pressure gradient becomes perpendicular to the existing fault line and the amount of pressure gradient changes spontaneously from lowest or highest value. Moreover, when a pressure tends to increase in this case there occurs a destructive one, and when it is decreasing, a moderate shock may occur. Following few examples may support this theory;
(2) When an extraordinary intense anticyclone covers the region surrounding a certain volcano even a slight variation of pressure may cause in many instances volcanic earthquakes and eruption. The examples of this case are found in the eruptions of Mt. Asama, Mt. Sakurazima, Mt, Bandai and others. All of these eruptions occurred, without exception, in the day of anticyclonic weather.