| Summary: | Abstract Hot spring discharge was linked to the 2011 Mw 6.6 Iwaki earthquake. Periodic surveys revealed that the discharge continued for more than 7 years, which is a rare and valuable long-term record of hot spring discharge triggered by an earthquake in a non-volcanic area. In terms of coseismic changes, based on a comparison of the spatial distribution of changes in the coseismic water head and calculated crustal volumetric strain using a fault model, hot spring water discharge was found to be caused by a change in the coseismic crustal volumetric strain. As for the postseismic changes, observations over 7 years revealed a gradual rise in the temperature and chloride ion concentration of the hot spring water. Such long-term hot spring discharge may be explained by the following two causes: the rise of thermal water from the deep part and the permeability changes along the hot spring channels.
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