Two-dimensional ionospheric total electron content (TEC) data during the time period from 00:00 on 2 July to 12:00 UT on 08 July, 2013, which was 5 days before to 1 days after a deep earthquake at 18:35:30 on 7 July, 2013 UT ( =7.2) with a depth of 378.8km 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 (Liu et al. 2006). 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. a density variance. 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 whiles 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 (EIA) resulted in the small principal eigenvalues, therefore the detection of TEC precursor was regardless of these background TEC anomalies.