Fig. 3
From: Earthquake early warning: what does “seconds before a strong hit” mean?
Station distribution for EEW operation: a the Japanese network stations by JMA, NIED (Hi-net and part of KiK-net), and JAMSTEC (DONET) (> 4000). Here, 30 KiK-net borehole station data around the Kanto region are included (Iwakiri et al. 2012); b the network stations by CISN, PNSN, and others that contribute to ShakeAlert in the West Coast region/USA (in beta-test phase with ~ 830 stations, as of July 2017)