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Basic Research on Seismic and Infrasonic Monitoring of the European Arctic
NORWEGIAN SEISMIC ARRAY (NORSAR) KJELLER
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This project represents a three-year research effort aimed at improving seismic and infrasonic monitoring tools at regional distances, with emphasis on the European Arctic region, which includes the former Novaya Zemlya test site. The project has three main components a to improve seismic processing in this region using the regional seismic arrays installed in northern Europe, b to investigate the potential of using combined seismicinfrasonic processing to characterize events in this region and c to carry out experimental operation, evaluation and tuning of the seismic threshold monitoring technique. The recent upgrade of the Spitsbergen seismic array, which has included the installation of five new three-component seismometers, as well as an increase in the sampling rate from 40 to 80 Hz, has resulted in significant improvements in high-frequency signal characterization as well as S-phase detection. Our studies have shown a remarkably efficient wave propagation from events near Novaya Zemlya across the Barents Sea. Significant signal energy at frequencies of up to 30 Hz and above has been observed, even for seismic events below a magnitude 3 at an epicentral distance of more than 1,000 km. In order to investigate if this same efficient propagation could be observed at the ARCES array in northern Norway, we have recently installed additional recording equipment at the center broadband element of ARCES, with a sampling rate of 100 Hz. Our initial results are similar to those seen at Spitsbergen. We should note that the available high-frequency data so far does not include events to the east and northeast of the ARCES array, and the high-frequency propagation from the Novaya Zemlya region to ARCES is therefore still unknown. As more data are accumulated, we may be in a position to carry out a detailed study of the high-frequency propagation characteristics for additional paths in the region. Analysis of data from temporary seismic stations installed as part of th
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