Response of microearthquakes to remote earthquakes is described in this paper. We analyze the microearthquakes observed in the Kakkonda geothermal field. The nine remote earthquakes were observed in Kakkonda in 2019. The geothermal reservoir in the Kakkonda geothermal field is 4 km to 5 km in size. Epicenters of the remote earthquakes were far more than 100 km from the Kakkonda geothermal field. The remote earthquakes occurred sufficiently far away compared to the size of the reservoir. Therefore, the remote earthquakes vibrated the geothermal reservoir uniformly. Event time series with microearthquake magnitude and source distribution of the microearthquakes were compared 24 hours before and 24 hours after occurrence of the remote earthquakes. It is difficult to find clear influence of the remote earthquakes on the event time series. On the other hand, microearthquake sources tended to be distributed in different zones before and after the remote earthquakes. The results of the source distribution analysis indicate that it is possible to characterize geothermal reservoirs by focusing on the response to remote earthquakes.

Hot springs were discovered at AK3 and AK4, situated southeast of Jigoku-numa during a water quality investigation of both stream and spring water in between Toritakisawa and Kasamatsu Pass along National Route 103 in the North Hakkoda Volcanoes region. These thermal waters were classified as volcanic waters based on the Cl–SO₄–HCO₃ triangular diagram. The δ¹⁸O and δ²H values of the thermal water strongly suggest a precipitation origin. Furthermore, the B/Cl ratio of the thermal water suggests that the reservoir of AK3 and AK4 may differ from that of the thermal water in Jigoku-numa.