Geoelectric fields at Kakioka (a), Kanoya (b), and Memambetsu (c). The northward (E
x; red line) and eastward (E
y; blue line) components of the geoelectric field from 1 January 2000 to 28 February 2011 at the three sites are shown. Hourly values are used. KAK, Kakioka; KNY, Kanoya; MMB, Memambetsu.