Two years of permanent deployment of seismic station LIVV, Antarctica

Livingston Island is one of the eleven islands of the South Shetland Archipelago which is separated from the Antarctic Peninsula by Bransfield Strait and from South America by the Drake Passage. In 1988 in the eastern part of the Island, the Bulgarian Antarctic Base “St. Kliment Ohridski” (BAB) was established. The Base works during the austral summers and accommodates scientists from different branches of the science. The first Bulgarian Polar Seismic Station LIVV was set in operation in 2014 as a seasonal station operating during the regular Antarctic expeditions. In 2019, the station was rebuilt on a new site one kilometer far from BAB. The seismological equipment was installed on a bedrock outcrop at the base of a hill. The equipment consists of broadband seismometer Guralp CMG40T with 30 s to 50 Hz flat velocity response and one short period 4.5 Hz Geophone. Thermo-insulation covers are mounted over the both sensors to ensure stable environment. The digitizer Reftek DAS-130/6 and the solar panel controller are installed close to the sensors in a thermo insulated box. The station is powered by a battery and solar panel. A GPS receiver ensures time synchronization. At the end of the XXVIII Bulgarian Antarctic expedition in March of 2020, the seismic station LIVV was set as permanent year-round operational Antarctic station. Using the recorded state of the health information and the registered seismic data, we analyzed the performance of the station LIVV. For the two years of permanent deployment, the seismic equipment works stable. The battery has retained its working capacity despite low temperatures and high humidity. There are interruptions in the recording when the sunlight is not high enough to charge the battery above 12V. After restoring the power supply, the equipment immediately is switched on in the normal registration mode. The temperature inside of the thermal box hasn’t dropped below 6⁰ C and the electronic components have worked in an optimal environment. The cycle operational mode of the GPS receiver is suitable set to ensure high accuracy time. The analysis of the recorded seismic data shows that the mode value of the ambient seismic noise, for longer periods greater than 1s, is 10-20dB below High Noise Model and for the shorter periods below 1 s it falls to -140dB. The noise level suggests good recording capabilities of the station especially in the short periods. This is proven by the large number of recorded earthquakes and events in the ice cover of the Livingston Island during the two years exploitation period. The analysis of the performance of the seismic station LIVV shows that the station is built on a stable foundation (bedrock), and the provided thermal insulation creates an optimal mode of operation of the seismic equipment. With an uninterruptible power supply, the seismic station will operate reliably and without interruption throughout the year, and the quality of the recorded data will be high enough to analyze the seismicity in the region and the behavior of the ice sheet of the Island.