Seasonal variations of seismic noise sources in the western Ross Sea, Antarctica

The Antarctic Ross Sea is one of the key regions for polar research activities. Research stations from several countries located at the cost are the base for inland expeditions. Even in the southern summer, the Ross Sea is party covered with drifting ice fields; this requires an icebreaker for all marine explorations. Therefore, large geophysical surveys in the Ross Sea are difficult. But the area is of special interest for seismologists: The Terror Rift in the western Ross Sea is a prominent neotectonic structure of the West Antarctic Rift System. It is located near the coast in the Victoria Land Basin and extends parallel to the Transantarctic Mountains. The rifting processes and the accompanying active onshore volcanism lead to increased seismicity in the region. The annual waxing and waning of the sea-ice and the dynamics of the large Ross ice shelf and nearby glaciers generate additional seismic signals. The Korean Polar Research Institute (KOPRI) and the Alfred-Wegener-Institut (AWI) conducted a pilot study off the Korean Jang Bogo research station in the Terra Nova Bay to explore seismicity and seismic noise in this region. Four broadband ocean-bottom seismometers (OBS) from the German DEPAS pool were deployed in January 2012 with the Korean research icebreaker RV Araon. Three instruments could succesfully be recovered after 13 months, the fourth OBS was not accessible due to local sea-ice coverage. It was retrieved one year late in January 2014. All stations recorded data of good quality, one station stopped after 8 months due to an recorder error. The OBS recovered in 2014 recorded more than 17 months of data until the batteries were discharged. In this contribution, we present preliminary results from a seismic noise analysis. We calculated monthly, weekly and daily probabilistic power spectral densities (PPSD) for all stations and channels. Strong seasonal variations are visible in the noise spectra and can be correlated with the sea-ice coverage in the region