伊豆半島沖地震 (1974-V-9) の温泉への影響

抄録

Recently, it is suggested that underground water plays an important part in generating the earthquakes. Studies are made in the present paper on changes in flow rate, temperature and heat capacity of hot springs distributed in southern Izu peninsula. These changes are considered to be related closely with the change of underground water caused by the Izu-Hanto-Oki (off the Izu peninsula, Japan) Earthquake (138°48′E, 34°34′N, h: 10km, M=6.9, May 9, 1974).
Both of the flow rate and temperature of these hot springs were found to be increased just after the earthquake.
Increases of flow rate and heat capacity discharged in the Shimogamo spa contiguous to the epicentral area began about 5.7 years before the earthquake. This abnormality reverted just before the earthquake. This period of about 5.7 years fit the period of precursory phenomena prior to the occurrence of the earthquake M=6.9 expected by “Dilatancy Model”. Moreover, the behavior of the variation bears a close resemblance to what is expected for the behavior of underground water as precursory phenomena prior to earthquakes by “Dilatancy Model”.