Fig. 4

Apparent relative velocity change a before and b after applying the seasonal corrections obtained from the ACFs recorded at Hi-net station N.MKGH. The colors of the circles indicate the correlation coefficients measured by the stretching technique. The black sine curve in Fig. 4a is fitted to seasonal variations. Red arrows indicate the origin times of the 2011 Tohoku and 2014 N. Nagano earthquakes. Gray dots represent one-hour averages of the RMS velocity amplitude in the 1–3 Hz passband of the E−W component of motion at station N.MKGH, where the measurement scale is given by the right ordinate. The area with a gray background indicates a period of recording system errors