Improvements to Seismic Monitoring of the European Arctic Using Three-Component Array Processing at SPITS

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1785/0120110109.

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Authors

Steven J. Gibbons , Johannes Schweitzer, Frode Ringdal, Tormod Kværna, Svein Mykkeltveit, Berit Paulsen

Abstract

The detectability of low magnitude seismic events in the European Arctic is determined primarily by the small-aperture International Monitoring System arrays ARCES and SPITS. In August 2004, the SPITS array was upgraded to a broadband array with an increase in the sampling rate from 40 to 80 Hz. Most important, however, for the detection and location of small-magnitude seismic events was the deployment of three-component instruments at six of the nine sites. Detection and correct classification of secondary phases are of paramount importance for events observed by only a small number of stations at regional distances; and, in the absence of the strong Lg phases typically observed for continental propagation paths, multiple three-component stations were deemed necessary to exploit the higher S-phase amplitudes anticipated on the horizontal sensors. We demonstrate improved signal-to-noise ratios (SNRs) for S phases on horizontal beams for several events close to Novaya Zemlya. Horizontal component f-k analysis improves direction estimates and phase classification for low-SNR signals. We demonstrate secondary phases that are misidentified by vertical-only f-k analysis but which are correctly classified by three-component array processing. A significant problem with array processing at SPITS is the overlap in slowness space of regional P and S phases. Phase identification is improved greatly by comparing the coherence between vertical traces with the coherence between horizontal traces. Considerations in the routine array processing of SPITS data are reviewed, including the need for elevation corrections in slowness estimation and the need to take into account azimuth-dependent variation of apparent velocity estimates for regional phases.

DOI

https://doi.org/10.31223/osf.io/f6qpz

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Keywords

Seismology, seismic, Arctic, Seismic monitoring, Svalbard, Barents Sea, CTBT, 3-component stations, Array Processing, European Arctic, IMS, Novaya Zemlya, P-waves, Regional Seismic Monitoring, Seismic arrays, SPITS, Spitsbergen, S-waves

Dates

Published: 2017-11-09 19:57

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License

Academic Free License (AFL) 3.0

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