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2013.03.08 update
[Expedition KY13-02: Backfilling of DONET seismometers and connection of a seafloor borehole observatory with DONET]
The expedition KY13-02 has been carried out from Jan. 18, 2013 to Feb. 10, 2013. The purpose of the expedition is to backfill the DONET seismometers with sands for improving the data quality and to connect a seafloor borehole observatory with the DONET for real-time observation.
Totally 13 seismometers were backfilled by sands during the expedition (other 7 seismometers have already been buried). As shown in Fig. 1, a newly developed sand feeder with a transparent container has played a large role in the backfilling work. Fig. 2 shows an example of the appearance before and after backfilling and Fig. 3 shows the effect of the backfilling: the noise level on the frequency longer than 10 seconds was reduced by approximately 10dB (max).
During the expedition, the connection of a seafloor borehole observatory with the Node D of DONET was also carried out. An interface unit was first installed on the platform of the borehole observatory and the cable-laying work from the Node D to the borehole observatory was then conducted, together with connecting the connectors with the Node D and the interface unit. It was confirmed that the real-time data reception can be worked correctly (click here for more information). The automated cable-laying system was used for the cable laying. The travelled distance and the length of paid out cable are approximately 8km and 8.5km, respectively.