Fig. 1.
From: Tracking the epicenter and the tsunami origin with GPS ionosphere observation
Time-differencing TEC from 29 GPS receiver-satellite pairs. The vertical axis denotes each pair with four alphanumeric (site name) and two numbers (GPS PRN number), divided by a hatch sign. Each curve denotes dTEC between every two adjacent measurements for 30-s sampling. The grid lines indicate the amplitude of dTEC (0.4 TECU for each grid; 1 TECU = 1016 m−3). The blue line and the red triangles indicate the origin time of the earthquake and the maximum dTEC, respectively.