Latitude-Time Total Electron Content Anomalies as Precursors to Japan's Large Earthquakes Associated with Principal Component Analysis

Figure 1

Location of GEONET receivers (red spot) and the epicenter of 18 earthquakes in Table 1 (black sopt). The epicenters of some earthquakes are not in the range of GPS network (see black spots); however, the TEC anomalies associated with the earthquakes can be detected, because the TEC anomalies are wider for lage earthquakes [1, 2].