Performance test of STS-seismograph in low temperature

• Main Authors: Masaki Kanao, Katsutada Kaminuma
• Format: Article in Journal/Newspaper
• Language: English; Japanese
• Published: National Institute of Polar Research 1994
• Subjects: Geography (General); G1-922; Antarctic; East Antarctica; Syowa Station; Antarc*; Antarctica; National Institute of Polar Research
• Online Access: https://doi.org/10.15094/00008862; https://doaj.org/article/40f144ab2b9d47bd83248acaac963430

Seismological observations by a set of three-component Streckeisen seismometers (STS-1V, -1H) have been carried on at Syowa Station (69.0°S, 39.6°E), East Antarctica since April 1989. Some troubles have occurred during the deployment of the STS seismographs. First, there is a relationship between temperature change and the drift of POS (position) and LP (long period) outputs of STS. Second, pulse-like noises (referred to as 'shift-noises' in this paper) have been observed on the vertical component of a rapid change in temperature greater than 3℃/day or immediately after arrival of a large earthquake. In order to investigate the mechanism of occurrence of shift-noises, a simultaneous observation by use of two vertical sensors was conducted during the 33rd Japanese Antarctic Research Expedition (JARE-33). It was revealed that the noises were generated not by poor attachment of the glass plate to the ground but by the behavior of the electric feed-back circuit and/or of the leaf-spring of the vertical sensor under low temperature. We performed some tests of the STS seismograph in the low temperature laboratory of National Institute of Polar Research to find the relationship between the drift of POS and temperature change. It was found by the experiments that there is a positive correlation between temperature change and drift; about 0.75V/℃ for the vertical component and 0.15V/℃ for the horizontal component. Shift noises similar to those at Syowa Station were also observed in the experiment in the low temperature laboratory. For the purpose of obtaining the response of the seismometer to the temperature variation at Syowa, LP digitized records in 1992 were decomposed into the drift component, tidal component, response to temperature variations, and noise series by making use of the BAYTAP-G program. The maximum addmittances to the temperature change are -1.3V/℃ for the vertical component and -0.003V/℃ for the NS component respectively.