Shown are Station E1TX seismograms recorded on 09 April 2018. The top image is the M4.6 (main shock) seismogram recorded 04/07/2018 at 12:16hrs UTC (7:16 am CST). The second image is the M4.3 (after shock) seismogram recorded 04/09/2018 at 10:22hrs (5:22 am CST). Notice the very similar patterns of the first few minutes of wave phases. This is a good sign that (1) the seismograph is working consistently, (2) the subsurface geology must not have changed significantly over the temporal scale, and (3) consistency bring confidence in measurements.