Earthquake warning in the sky
Controversial observations suggest that electrical charges redistribute in the outermost layer of the atmosphere in a characteristic manner prior to an earthquake.
On the afternoon of March 11, 2011, the ground in geophysicist Kosuke Heki's office at the University of Hokkaido in northern Japan began to shake. The individual thrusts came at long intervals, each lasting a few seconds. Heki is familiar with earthquakes and studies the distribution of electrical charges in the sky after such an event. What he felt now seemed to be a strong but distant earthquake. He still hoped that the data might help his research. Then someone turned on the news - and Heki's curiosity turned to horror.
The tremors came from the largest earthquake in modern Japanese history, the devastating magnitude 9.0 Tōhoku earthquake. It killed an estimated 20,000 people and caused hundreds of billions of euros in devastation. As a result of the quake, a tsunami hit the Fukushima Daiichi nuclear power plant, triggering the worst nuclear disaster in a quarter century.
While emergency teams evacuated the affected areas and tried to save lives, Heki could only wait for phones and internet connections to be restored in the area. Two days later it was time. Heki downloaded and combed through satellite data on the atmosphere over the Tōhoku region. As he had expected, the electrons in the ionosphere, the outermost layer of the atmosphere permeated by charged particles, showed an anomalous distribution ten minutes after the event. But he couldn't reconcile his previous findings with the new data just by looking at the period immediately after the quake. So he expanded the scope and also included the measurements from an hour earlier. What the researcher then saw took his breath away: a subtle increase in electron density over the epicenter of the quake - 40 minutes before the event.
Were these statistical outliers in the data? Wrong values of the instruments? Or was there more behind it? Scientists have long been looking for reliable harbingers of earthquakes, telltale signs that will allow timely alerting of people. If the behavior of the electrons in the ionosphere is such an indicator, it could save many lives…