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Abstract
Two-dimensional ionospheric total electron content (TEC) data during the time period from 00:00 on 2 July to 12:00 UT on 8 July 2013, which was 5 days before to 1 day after a deep earthquake at 18:35:30 on 7 July 2013 UT (Mw = 7.2) with a depth at about 378.8 km in Papua New Guinea, were examined by two-dimensional principal component analysis (2DPCA) to detect TEC precursor related to the earthquake because TEC precursors usually have shown up in earlier time periods. A TEC precursor was highly localized around the epicenter from 06:00 to 06:05 on 6 July, where its duration time was at least 5 minutes. Ionizing radiation radon gas release should be a possibility to cause the anomalous TEC fluctuation, e.g., electron density variation. The plasma might have large damping at that time to cause TEC fluctuation of short time, and the gas released with small amount in short time period, and 2DPCA could identify short time TEC fluctuation while the fluctuation lasted for a long time. Other background TEC anomalies caused by the geomagnetic storm, small earthquakes and non-earthquake activities, e.g., equatorial ionization anomaly resulted in the small principal eigenvalues, therefore the detection of TEC precursor was regardless of these background TEC anomalies.
Acknowledgments
The author is grateful to NASA GDGPS for their TEC data. This article is in memory of my German life. I was a student Germany (1996–2000). Also it is in memory of my wife, Cheng-Ling Liu and her three daughters. I wish they have bright future after I left and her third daughter can go to German for her musical study because I was only visitor (2008–2013) for five years.