Seismic observations at Syowa Station (SYO) have been carried out mainly by two types of seismometers, that is, one called a HES with 1.0 s natural period of the pendulum and the other called a PELS with 12.0 s natural period. These three-component short-period and long-period seismographs had been operated since 1967 (Kaminuma et al., 1968). In later year, a three-component broadband seismometer (Streckeisen STS-1) with the digital recording system has been operating since May 1990 (Nagasaka et al., 1992).

The seismographic vault constructed in March 1970 (69ｰ00'31.7"S, 39ｰ35'31.6"E, 20 m above mean sea level ; Kaminuma & Chiba, 1973) was closed at the end of 1997 season because of a superannuating for inner side of the vault by continuous flow in of water from walls in summer and its frozen in winter. Therefore, all the sensor-instruments were moved to the new seismographic hut in April 1997, which was constructed in 1996. PELS seismographs were stopped to recording in the new hut, because of its frequency response is fully covered by STS-1 velocity signal outputs.

The new seismographic hut locates about 200 m north from the old vault, with geodetic coordinates of 69ｰ00'24.0"S, 39ｰ35'06.0"E and the elevation is 20 m above mean sea level. Since the broadband seismographs are largely affected by the change of temperature and atmospheric condition, then the sensor room was covered doubly by adiabatic walls, with a surface covered by Titanium to keep the constant temperature in the room.

Seismic signals of the short- period (HES) and broadband (STS-1) seismometers in the new hut are transmitted to the Earth Science Laboratory (ESL) via analog cable of 600 m in length. The cables were mounted on racks, which connect the main buildings of Syowa Station, and laid parallel with the other electric power cables of the Station.