Figure 7
From: Post-seismic ionospheric response to the 11 April 2012 East Indian Ocean doublet earthquake
Detrended TEC, wavelet frequency spectrum, and trapped fluctuations. (a) Detrended TEC from PRN 32 observations at site umlh at 08:00–12:00 UTC (top panel). Wavelet frequency spectrum for the same is shown in bottom panel. The dominant presence of an acoustic frequency (4.49 mHz) during the main shock clearly indicates that the observed TEC fluctuations were produced by acoustic wave frequencies, similar to the aftershock-induced fluctuations. Here, however, the dominant frequencies vary from approximately 4.0 to 6.0 mHz. (b) The acoustic trapped mode after the main shock was also observed for approximately 50 min. The top panel shows trapped fluctuations with high-time resolution, and the bottom panel shows the wavelet frequency spectrum.