Recently, the Hatchobaru geothermal electric power station of Kyushu Electric Power Co. started its commertial operation on June 1977, under the prescribed power of 50, 000KW. In prior to the completion of the full scale Hatchobaru Power Station, a geothermal power station had been operated since August 1963 at Ohtake, about 2 km distant from the new station to the north. Together with the increase in the development of power production it was planned to improve the micro-earthquake observation network. A new network is composed by one base station and 6 branch stations distributed within an area of 20×20km, in which the Hatchobaru station is acting as the base station locating nearly in the center of the other stations. Each branch station is equipped with one vertical seismometer and is connected to the base station by telephone lines. In the base station all neccesarry devices for micro-earthquake observations are prepared including memory unit, trigger unit, amplifying unit, for-each respective station and a cloock system as well as a recording system. The recording system in Hatchobaru base station is so arranged that the six seismograms of all the seismic stations could be reproduced on one sheet of paper side by side. In doing so reading of seismograms and locating of epicenters could be realized most easily with high acculacy. In this report there are described the newly developed telemeter system for observing the micro-earthquakes in the Hatchobaru geothermal area, together with the some results obtained in the course of the first 8 months test run. These results fairly a satisfactory operation.

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Quantitative informations about temperature, concentration and escaping velocity of the volcanic smoke from the craters will or may provide some parameters necessary to estimate the grade of volcanic activity or the heat energy stored in the volcanic areas. This paper proposes a passive type of volcanic gas-or steamjet-eruption velocity sensor, which is based on the optical image-angular-velocity sensing technique performed by the use of a plus-minus stripformed detectors, linear arry, with either a silicon photovoltaic detector or a pyroelectric detector, and uescribes both a signal processor making it possible to improve the measurement accuracy and some experimental results exhibiting the feasibility of the measurement.

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Friction welding method was applied for connecting a steel tube(STM-R80) for drilling and tool joints(SCM-3). At the first stage of the experiment, owing to the fast cooling velocity in and around the welded part, the hardness came up to Hv500 maximum, hence, annealing treatment was required. To improve it, the friction time was prolonged to give a wide heat effect range on thewelded part, which was then cooled down, slowly.As a result, the hardness ofthe welded part was reduced to a maximum of Hv350, and a narrow rang of hardness distribution was obtained around them. In this case, annealing treatment could be omitted. Test pieces welded under the latter condition were used for tention, bending and torsion tests. From these three tests, we could get satisfactory results for practical use.

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