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Changes in VHF radio reception give early warning of volcanic eruptions and
earthquakes, says Yoshio Kushida of Japan, who is patenting a radio device for
forecasting earthquakes (EP 819 951). The effect has been noticed before (
New¿ìè¶ÌÊÓƵ, 23 December 1995, p 15). Kushida believes that tension in the
Earth’s crust creates a piezoelectric effect that alters the plasma density of
the ionosphere, the upper layer of the atmosphere. He listened to the output of
a radio station at Sendai to see how reception was affected by local
earthquakes. He says changes in radio reception can give up to five days’
warning of an earthquake.