Seismometer station VNA2 at "Watzmann" (Halfvarryggen)
Seismographic station VNA2 called "Watzmann" is located about 45 km southeast of NM-III on the ridge of Halvfarryggen ice rise at a height of approx. 350 m above sea level.
Seismology
We operate a small local network comprising three stations with international codes VNA1, VNA2 and VNA3. Station VNA1 is inside the geophysics observatory near NM-III. The stations VNA2 and VNA3 are in distances of approx. 45 km and 85 km located on the ridges of Halvfarryggen and Söråsen ice rises. Here the ice is laying on solid rock and does not float on the sea like the Ekström ice shelf. Seismic recordings on an ice shelf suffer from a strongly decreased data quality. Close to the coast, station VNA1 is often contaminated by predominately long period noise signals originating from ocean swell or strong wind sea, especially during the summer months. Floating ice sheets, crack-forming in the fast sea ice, stranding or colliding icebergs are further noise sources. They sometimes can make it impossible to extract earthquake signals from the recordings. Additionally, shear waves can't penetrate the water layer so only a part of the incoming seismic waves are visible. Stations located furthermore inland and on the mainland show a much better data quality, even during periods with rather strong winds. VNA2 and VNA3 are therefore rather important. However, during polar winter we sometimes encounter problems with the electrical power supply.
Since 1997 we have operated a small aperture detection array. It comprises 15 vertical 1-Hz seismometers located on three concentric rings. The 3-component broadband sensor is placed in the center of the array which has a diameter of almost 2 km. It is believed that it is the only array of this kind in Antarctica. Array techniques like beam forming can help to detect very weak earthquakes even under noisy conditions and improves thus the detection capability of the entire network. The array allows for incoming seismic waves of epicenters with distances up to 2000 km to determine their direction (“backazimuth”) and their velocity (resp. “slowness”, the reciprocal velocity) with sufficient accuracy. Both parameters can be used to improve the the localization accuracy of these epicenters.
Since 1997 the associated broad band station SNAA at the South African base SANAE-IV is also included into our local seismographic network. Station is now under control of the council for Geoscience, SA and is operated in cooperation with the Federal Institute for Geosciences and Natural Resources (BGR). SNAA recordings are continuously available online and are included into the NM-III network. Since early 2016 also recordings from the Norwegian base TROLL are retrieved regularly and added with a one-day delay.
Currently we operate four more temporary seismic stations in the western Dronning Maud Land. These stations are NOVO at the Russian station Novolazarevskaya, SVEA at the Swedish summer station, WEI at the Weigel Nunatak in the Kottas mountains and KOHN at Kohnen-Station on the inland ice. These stations are unattended and operate completely autonomously and are serviced only once a year during southern summer. During these visits data stored on CF-cards are retrieved and later migrated into the databases at NM-III and AWI Bremerhaven.
These stations together form a rather extended regional seismographic network in western Dronning Maud Land. Detection threshold should be significantly reduced and localization accuracy significantly improved, especially for weak regional earthquakes.
Data access
Data is transferred online from NM-III to AWI Bremerhaven and further on to GFZ in Potsdam, which is the national data archive for seismic data.
Recordings from the local seismographic network of NM-III can be requested HERE (network ID is AW).
Data format is the international widely used mseed format. Dataless seed volumes with all necessary meta data are also available.
Current and archived plots of seismic recordings from VNA2 and VNA3 can be seen HERE.
Seismometer station VNA3 at "Olymp" (Søråsen)
Seismographic station VNA3 called “Olymp” is located about 85 km southwest of NM-III on the ridge of Söråsen ice rise at a height of approx. 500 m above sea level.
Seismometer station SVEA
Seismographic station SVEA at the identically named Swedish summer base in the Heimefrontfjella mountain range. Svea is located about 450 km southwest of NM-III. It is an autonomous operating, unattended station with data retrieval and station service once a year during summer.