Fig. 3

Epicenters of the analyzed events and the examined events. a The magnitude–epicentral distance relation of groundwater level change in the Oi well. The broken line is the referenced magnitude–epicentral distance line which indicates the minimum magnitude for the groundwater level change in Oi well in 2012. The straight line is the basic line, for earthquakes above which we checked the groundwater level in the Oi well from 2011 to 2016. The solid and open squares show the events which caused the groundwater level changes larger than or equal to 5 cm in the Oi well and those less than 5 cm, respectively. The open triangles show the events (Mw \(\ge 6)\, {\text{in}}\, 2012,\) which we examined and found no groundwater level change in the Oi well. The crosses show the events, which we examined and found no groundwater level change in the Oi well for the period from 2011 to 2016. b The circles indicate the epicenters of the analyzed events. The number in the circle indicates the event number in Table 2. The plus marks show the events from 2011 to 2016, which accompany no groundwater level change or the groundwater level change less than 5 cm. The top figure shows the global map, and the bottom figure shows the area around Japan