The time variation of seismic velocity relative to the averaged pre-earthquake value are displayed. Each panel shows the central date within the 30-day window: (a) 8 March, (b) 1 May, (c) 1 June, and (d) 1 October 2016. Warm colors indicate regions where seismic velocity was decreased. During the 2016 earthquake, seismic velocity around the seismogenic Hinagu-Futagawa fault system and Mount Aso decreased greatly. Cold colors indicate regions where seismic velocity was
increased. Seismic velocity at Mount Aso recovered rapidly and was
faster than the pre-earthquake velocity after the eruption. The date
described above shows the central date within the 30-day window.
Yellow or white dots are Hi-net stations.