Earthquakes and icequakes recorded on drifting ice floes as seismometer platforms
Recording the seismic activity of polar regions often requires to install seismometers on ice. Across the Arctic Ocean, seismological experiments are only feasible with seismometers mounted on drifting ice floes, which cover year-round the central Arctic Ocean to more than 90%. During 4 deployments, we acquired 72 days of continuous seismic data on ice floes using small-aperture seismic arrays consisting of 3-4 seismometers. Here we present the variety and characteristics of seismic signals recorded on the ice floes. We obtained clear P-wave signals from teleseismic earthquakes of about magnitude M>6. Distant earthquakes originating in the Arctic Ocean can be reliably recognized by their T-waves. The background noise at the ice floes is larger than that of land based stations especially for frequencies < 0.5 Hz. At higher frequencies, local earthquakes as small as about M 0-1 can be detected. A sharp P-onset, a difficult to identify SP-phase and a train of multiply reflected arrivals from the water column are characteristic for local earthquakes. The earthquake records are intermixed with numerous icequakes travelling horizontally across the array of receivers. They often exhibit a long-period signal coda. The distinction between seismogenic and cryogenic signals is difficult and has been done manually in all our surveys. Apart from short transient signals, the ice floe records include long-lasting tremor signals. In spectrograms, an increased signal energy in a narrow frequency band of about 2-5 Hz is visible for hours. Occasional harmonic tremor signals which are well-known from Antarctic icebergs might be attributed to distant Greenlandic icebergs.
AWI Organizations > Geosciences > (deprecated) Junior Research Group: MOVE
ARK > XXIV > 3