2019 Yamagata earthquake【QE】

Website launched: 21st June, 2019

An earthquake 6.8 Mw(according to JMA) occurred on 18th June 2019 at 10:22 p.m. JST,  off the coast of Yamagata Prefecture, northwest Japan.

*All figures/pictures/movies should be credited as: “Earthquake Research Institute, The University of Tokyo” when cited.

Simulation of seismic wave propagation for the M6.7 Off Yamagata earthquake of 18 June 2019
(Shunsuke TAKEMURA and Takashi FURUMURA)

To investigate properties of the seismic wave propagation during the 2019 Off Yamagata earthquake (M6.7) of 18 June 2019, we conducted a numerical simulation of seismic wave propagation by using a source model of the NIED AQUA CMT and a 3D subsurface structure model (Fig. 1). The simulated seismograms for periods of 12.5-100 s agreed well with observed ground motions at F-net stations (Fig. 2). Simulated seismic wavefield demonstrates that strong ground motions spread from the seismic source to east-southeastward and west-northwestward directions due to effect of source radiation pattern. Then, strong amplifications and elongation of ground motions occurred in thick sedimentary basins (e.g., Toyama, Niigata, Shonai and Kanto basins; see Fig. 1).

Fig. 1. Seismic wave propagation obtained by the numerical simulation. Red and green colors represent intensities of P and S waves, respectively.

Fig. 2. Simulated seismograms using a source model of AQUA-CMT from NIED (blue focal sphere in the map) and a 3D subsurface structure model (Koketsu et al. 2012). Simulated and observed seismograms are illustrated by blue dashed and gray solid lines, respectively. A band pass filter (12.5-100 s) is applied.

Acknowledgement: We used NIED AQUA-CMT catalog and F-net data. Numerical simulation of seismic wave propagation was conducted by using an open 3D finite-difference code (OpenSWPC; Maeda et al. 2017).