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Published October 1969 | Published
Journal Article Open

Array data processing techniques applied to long-period shear waves at Fennoscandian seismograph stations


Array data processing is applied to long-period records of S waves at a network of five Fennoscandian seismograph stations (Uppsala, Umeå, Nurmijärvi, Kongsberg, Copenhagen) with a maximum separation of 1300 km. Records of five earthquakes and one underground explosion are included in the study. The S motion is resolved into SH and SV, and after appropriate time shifts the individual traces are summed, both directly and after weighting. In general, high signal correlation exists among the different stations involved resulting in more accurate time readings, especially for records which have amplitudes that are too small to be read normally. S-wave station residuals correlate with the general crustal type under each station. In addition, the Fennoscandian shield may have a higher SH/SV velocity ratio than the adjacent tectonic area to the northwest.SV-to-P conversion at the base of the crust can seriously interfere with picking the onset of Sin normal record reading. The study demonstrates that, for epicentral distances beyond about 30°, existing networks of seismograph stations can be successfully used for array processing of long-period arrivals, especially the S arrivals.

Additional Information

Copyright © 1969, by the Seismological Society of America. Manuscript received May 22, 1968. This work was done while the author was at the Seismological Institute, Uppsala, Sweden, with the support of Sweden-America Foundation and Fulbright-Hays grants. The research was partially sponsored by the Cambridge Research Laboratories of the Office of Aerospace Research, United States Air Force, through its European Office, as part of the Advanced Research Projects Agency's project VELA UNIFORM, under contract AF 61(052)-702. Professor Markus Båth suggested this project, and his support and advice throughout the work is greatly appreciated. Dr. Bo Jansson of the Swedish Defense Research Institute supplied helpful advice and some computer programs. The author wishes to thank the directors of the seismological institutes at Copenhagen, Denmark; Bergen, Norway; and Helsinki, Finland, for the use of seismic recordings and the Swedish Defense Research Institute in Stockholm for the use of their facilities. Records from UPP were made with instruments on loan from Lamont-Doherty Geological Observatory, Columbia University, as part of the IGY program. The author is currently receiving support from NASA Research Grant NGR 05-002-069 at the California Institute of Technology.

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