5:15 PM - 6:30 PM
[MAG37-P01] The upgrade of the CTBT Auxiliary Seismic Stations in Japan
Keywords:CTBT, International Monitoring System, National Data Centre, Seismology
Japan Weather Association (JWA) is working as the Comprehensive Nuclear-Test-Ban Treaty (CTBT) National Data Centre-1 (NDC-1) of Japan. NDC-1 has two main roles. The first role is analyzing waveform data related to seismic and infrasound waves and providing advices to the Ministry of Foreign Affairs from a technical perspective. The another one is the Station Operators (SO) of the International Monitoring System (IMS) stations in Japan. There are 1 Primary Seismic (PS) station, 5 Auxiliary Seismic (AS) stations and 1 Infrasound (IS) station in Japan and NDC-1 is working for operation and maintenance of these 7 stations.
AS stations used to branch the signals of the broadband sensors owned by the Japan Meteorological Agency (JMA) and were using these signals as IMS data. But it turned out that there are some difficulties in sensor calibration from the CTBT side equipment with technical surveys conducted several times in the past. The IMS seismic observation system operation manual says that the sensor should be calibrated once a year, so in order to carry out the calibration efficiently, it is necessary to prepare the CTBT unique sensors separately from the sensors of the JMA. Therefore, over the last two years, including the construction preparation period, sensors (Guralp CMG-3T) for CTBT were installed near the existing observation sites for all five AS stations in Japan.
As a preliminary step to the installations of the sensors, 50 cm x 50 cm piers for seismic sensors were installed, which were designed according to the current situations of each site. When the installation of the seismic sensor, the sensor was placed on the pier and oriented and leveled. A metal cover was attached to prevent magnetism and a heat insulating material is wrapped around it to prevent temperature changes. The on-site calibration was performed at each site by NDC-1 after installation. After NDC-1 on-site work, the station has passed the test period by CTBTO side and it was returned to operation.
As a result of this upgrade, the new sensors for CTBT were installed at all 5 AS stations, and the annual calibration and other work related to maintenance and improvement of data quality can be performed remotely by NDC-1. In this presentation, we will introduce the details of this upgrade work.
AS stations used to branch the signals of the broadband sensors owned by the Japan Meteorological Agency (JMA) and were using these signals as IMS data. But it turned out that there are some difficulties in sensor calibration from the CTBT side equipment with technical surveys conducted several times in the past. The IMS seismic observation system operation manual says that the sensor should be calibrated once a year, so in order to carry out the calibration efficiently, it is necessary to prepare the CTBT unique sensors separately from the sensors of the JMA. Therefore, over the last two years, including the construction preparation period, sensors (Guralp CMG-3T) for CTBT were installed near the existing observation sites for all five AS stations in Japan.
As a preliminary step to the installations of the sensors, 50 cm x 50 cm piers for seismic sensors were installed, which were designed according to the current situations of each site. When the installation of the seismic sensor, the sensor was placed on the pier and oriented and leveled. A metal cover was attached to prevent magnetism and a heat insulating material is wrapped around it to prevent temperature changes. The on-site calibration was performed at each site by NDC-1 after installation. After NDC-1 on-site work, the station has passed the test period by CTBTO side and it was returned to operation.
As a result of this upgrade, the new sensors for CTBT were installed at all 5 AS stations, and the annual calibration and other work related to maintenance and improvement of data quality can be performed remotely by NDC-1. In this presentation, we will introduce the details of this upgrade work.