Fig. 10
From: Earthquake early warning: what does “seconds before a strong hit” mean?
Comparison between JMA seismic intensities estimated in the real-time EEW scheme of JMA (left) and calculated intensities using data from YCSMN stations (right). The procedure of intensity estimation is explained in Appendix. Here, we used the site amplification map of the Japan Seismic Hazard Information Station (J-SHIS by NIED) to obtain site amplification coefficient at each grid (250 m interval) for the JMA estimates. The JMA intensity scale (IJMA) is shown at nine levels from 1 (white) to 7 (purple): a EQ1: July 23, 2005 NW Chiba Pref. (Mw5.9, depth 73 km; see Table 3 in Appendix). The IJMAs estimated in the EEW scheme are 4 (green) in the whole area, regardless of different site conditions. The actual IJMAs calculated with data from the YCSMN (142 stations) vary from 5− (yellow) on the northeast side to 3 (light blue) on the southwest and northwest sides. b EQ2: March 11, 2011 off the Pacific Coast of Tohoku (Tohoku-Oki; Mw9, depth 24 km). The IJMAs estimated for Mj8.1 using the real-time EEW algorithm in 105 s after P-wave detection were 4 (green) in the basin and 3 (light blue) on the hillside. The actual IJMAs calculated at the YCSN stations (118 stations) range from 4 (green) to 5+ (orange)