Features related to the stations of the Euro network. (a) Distribution of 151 stations (black triangles and a black diamond) throughout Europe that compose the Euro network. The large black diamond with the label “ZAG“ indicates the reference station. (b) Examples of the vertical-component high-quality normalized seismograms from 25 stations with a time length of 60 s, which are high-pass filtered with a cut-off frequency of 0.2 Hz. (c) The array response function of the Euro network to the source region at 0.2 Hz. The black star indicates the epicenter of the Tohoku Earthquake. The dashed line depicts the Japan trench. The contour lines indicate the normalized beam energy with a interval of 0.1.