Interpretation of Self-potential Survey Results in the Kakkonda Geothermal Area, Iwate Prefecture

Abstract

Self potential surveys were carried out in the Kakkonda geothermal area, Shizukuishi-cho, Iwate prefecture, from 1979 to 1981. The effects of artificial structures and activity of fumaroles on the self potential were investigated and the extent of geothermal reservoir was discussed by the results of self-potential method and the other geophysical prospecting data. The following results are obtained.(1) The self-potential profiles were obtained three times along a traverse in the area. Despite the almost one year gap in the time of data collection, the profiles are sufficiently similar to demonstrate that the self-potential data obtained by the proper field procedure are reproducible.(2) Self-potential anomalies ranging in amplitude from 100mV to 400mV were observed arround the ferroconcrete structures. This implies that data correction is needed if the self-potential survey is conducted near artificial structures.(3) There are no significant anomalies associated with the activities of fumaroles and hot spring in the area investigated.(4) The area of negative anomalies at the northern part of Takinoue tunnel and at the northeastern part of Kakkonda river, coincide roughly with the areas of low resistivity, high temperature and high radiometry. This result may give us an index to determine the extent of geothermal reservoir.