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Solid Earth An interactive open-access journal of the European Geosciences Union

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doi:10.5194/se-2016-90
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
12 Jul 2016
Review status
This discussion paper is under review for the journal Solid Earth (SE).
Structure of Suasselkä Postglacial Fault in northern Finland obtained by analysis of local events and ambient seismic noise
Nikita Afonin1, Elena Kozlovskaya2,3, Ilmo Kukkonen4, and DAFNE/FINLAND Working Group* 1Federal Centre for Integrated Arctic Research RAS, Arkhangelsk, Russia
2Oulu Mining School, POB - 3000, FIN - 90014, University of Oulu, Finland
3Geological Survey of Finland, P.O. Box 96, FI - 02151, Espoo, Finland
4Department of Physics, University of Helsinki, P.O. Box 64, FI-00014, Helsinki, Finland
*A full list of authors and their affiliations appears at the end of the paper .
Abstract. Understanding inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä post-glacial fault (SPGF) that was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised the area of about 20 to 100 km and consisted of 8 short-period and 4 broad-band 3-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September, 2011–May, 2013. Recordings of the array have being analyzed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä Gold Mine. As a result, we found several dozens of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green’s functions between pairs of stations in the frequency band of 0.1–1 Hz and to calculate correspondent surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curves inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low velocity region as a non-healed mechanically weak fault damage zone (FDZ) that remained after the last major earthquake that occurred after the last glaciation.

Citation: Afonin, N., Kozlovskaya, E., Kukkonen, I., and Working Group, D.: Structure of Suasselkä Postglacial Fault in northern Finland obtained by analysis of local events and ambient seismic noise, Solid Earth Discuss., doi:10.5194/se-2016-90, in review, 2016.
Nikita Afonin et al.
Nikita Afonin et al.
Nikita Afonin et al.

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