Fig. 6
From: Earthquake early warning: what does “seconds before a strong hit” mean?
Warning time and intensity distribution for the 2011 Tohoku-Oki earthquake. Here, the warning time is the time interval between the alert issuance and ground shaking arrivals estimated on concentric circles. This figure was copied from “Report of earthquake early warning alerts” (in Japanese) at: http://www.data.jma.go.jp/svd/eew/data/nc/rireki/201103.pdf#page=4, and slightly modified with location labels of A1 to A6, and other labels into English. The scale of IJMA 4 to 7 is color coded below the map. At location A1 IJMA6−, shaking arrived 6 s after the initial alert was issued. Likewise, strong shaking of IJMA7 at A2 and IJMA6+ at A3 in 19 s, IJMA6+ at A4 in 35 s, and IJMA6+ at A5 in 49 s, respectively. Location A6 is in Chiyoda-Ku/Tokyo where shaking of IJMA5+ arrived in 67 s after the initial alert