Earth Planets Space, Vol. 58 (No. 6), pp. e21-e24, 2006E-LETTER
Takeshi Nishimura1, Mie Ichihara2, and Sadato Ueki3
1Department of Geophysics, Graduate School of Science, Tohoku University, Japan
2Earthquake Research Institute, University of Tokyo, Japan
3Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Japan
(Received March 13, 2003; Revised April 26, 2003; Accepted April 28, 2003; Online published May 26, 2006)
In this study we conducted observations of the Onikobe geyser, NE Japan, by deploying a tiltmeter and an acoustic sensor close to the vent, a flow pressure sensor at the conduit exit, and measuring water temperature at ground level. The data from these instruments are consistent with the model of geysers which involves effusion process of boiling due to depressurization. During the observation period, the geyser generally effused water for about 90 s every 10 mins, although during certain periods these times randomly shortened to about 60 s and 6 mins, respectively. Tilt records show a strong correlation with the short and long effusion times, reflecting water movement in at least two chambers beneath the vent. We are able to empirically predict the duration of effusion from tilt data, although flow pressure does not vary with effusion time.
Key words: Geyser, Onikobe, effusion, tilt, boiling, depressurization.