In this paper the reasonable distridution of the regional station net has been discussed in view of furnishing with seismographs, and the results have been obtained as follows:
(1) If each station of the network, in which the distance between neigboring stations is about 50 kilometres, is furnished with four visible short period recording seismographs (V₀=1.0×10⁵, 1.5×10⁴, 2.5×10³, 4.0×10², and if at the same time, several stations, the distance bet ween which is less than 200 kilometres, are furnished with one moderately strong-motion seismograph of V₀=50 each, the hypocentres of the earthquakes with magnitude over 1 (M_s ≥ 1) within the network may be determined.
(2)If the distance between neigboring stations is less than 150 kilometres and all of them have been furnished with the above-mentioned instruments, the hypocentres of the earthquakes with M_s ≥ 1.5 maybe determined.
On the basis of the above-mentioned results and the present station conditions in Gansu province, the project of the reasonable distribution of the station nets in Gansu has been is suggested. According to this project, in the station net of the east region of Gansu, the hypocentres of the earthquakes with M_s ≥ 1.5 can be probably determined, but in the Gansu Corridor (the western part of Gansu), the hypocentres of the earthquakes with M_s ≥ 2.0 which occur along the long corridor zone in the east region to Jaryuguan (嘉峪关) can be determined probably.