Study: Massive earthquakes may be possible to predict

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Japanese University Detects Atmospheric Precursor To 2011 Megaquake

Most scientists believe that earthquakes are inherently unpredictable, and reports of various kinds of earthquake precursor signals have been difficult to verify. However, in a new study, a researcher from Hokkaido University in Sapporo has reported a possible ionospheric precursor to the devastating magnitude 9 Tohoku earthquake in Japan on 11 March, 2011.

Analysing data from the Japanese GPS network the team, Kosuke Heki from the University’s Department of Natural History Sciences has detected an increase in the total electron content (TEC) in the ionosphere above the focal region of the earthquake beginning about 40 minutes before the quake.

The TEC enhancement reached about 8 percent above the background electron content. The increase in TEC was greatest above the earthquake epicentre and diminished with distance from the epicentre.

The researcher, whose report is published in the journal Geophysical Research Letters, also analysed GPS records from previous earthquakes and found that similar ionospheric anomalies occurred before the 2010 magnitude 8.8 Chile earthquake, possibly the 2004 Sumatra magnitude 9.2 earthquake, and possibly the 1994 magnitude 8.3 Hokkaido earthquake. However, TEC enhancements were not seen before smaller earthquakes.

Although previous studies have shown that earthquakes could trigger atmospheric waves that travel upward and disturb the ionosphere, it is unclear how an ionospheric disturbance could occur before an earthquake begins. In addition, the ionosphere is highly variable, and solar storms can trigger large TEC changes, so non-earthquake causes of any TEC enhancement need to be ruled out.

Kosuke Heki states that, unlike previously suggested earthquake precursors, the TEC enhancement before the Tohoku quake had obvious spatial and temporal correlation between the quake and precursor signal as well as clear magnitude dependence.

Scientists agree that further research is needed to verify that TEC enhancements can indeed be a precursor to large earthquakes.