[S03-P] Poster

[S03-P-08] A temporal and spatial change in seismic velocity caused by the 2016 Kumamoto earthquake using cross-correlations of ambient seismic noise

^○Hiro Nimiya¹, Tatsunori Ikeda², Takeshi Tsuji^1,2 (1.Earth Resources Engineering, Kyushu University, Fukuoka, Japan, 2.WPI-I2CNER, Kyushu University, Fukuoka, Japan)

Revealing the damage of seismogenic faults caused by earthquakes is important to understand the condition of the seismogenic faults and to predict the seismogenic fault behavior.In recent years, some researches demonstrate that the seismic velocity change at the large earthquake is associated with variation of subsurface stress and crust damage.To estimate temporal variation of the subsurface associated with the 16 April 2016 Mw 7.1 Kumamoto earthquake, we estimated spatial and temporal variation of seismic velocity by using ambient seismic noise recorded by a high-sensitivity seismograph network (Hi-net) for a year of December 2015 to November 2016. We computed cross-correlations of ambient seismic noise records to retrieve virtual seismogram propagating between the pair of stations, and applied the stretching interpolation technique to estimate the temporal change in seismic velocity. Our results show that the seismic velocity near the Futagawa-Hinagu fault zone and volcanic regions clearly decreased at the Kumamoto earthquake. The velocity reduction near the fault zone (~0.4%) could be occurred due to the damage of the fault. The largest seismic velocity reduction observed around Mount Aso (~0.8%) might be caused by pressurized volcanic fluids. Furthermore, the decrease in seismic velocity gradually returned to the pre-earthquake value, suggesting gradual healing of the damage caused by the earthquake.