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GNSS observations in mining tremors analysis

13-09-2020

Among earthquakes, natural and anthropogenic ones can be distinguished. The Republic of Poland is located in an intraplate area where natural earthquakes are very rare. On the other hand, areas with a high density of active underground mining are threatened with induced seismicity. Seismic tremors occur regularly in the underground mining areas, and there are several hundred events annually with magnitudes greater than 2, with maximum magnitudes reaching 4. As mining tremors are shallow and very frequent, they cause damage to infrastructure.

Mining tremors are mainly monitored with seismological instruments, however, the progress in the field of satellite observations allows to observe them also with the high-rate GNSS observations, which are more and more often used to observe vibrations during large earthquakes and in structural monitoring, e.g. bridge vibrations. In contrary to classical GNSS observations, in vibrations monitoring the observations’ sampling rate is up to 100 Hz, which are processed in kinematic mode, resulting in epoch-to-epoch positions. The infrastructure that is developed within the EPOS-PL project led us to record one of the biggest mining tremors on the LGOM area, that occurred on January 29, 2019, with magnitude 3.7. Due to the optimal localisation of GNSS stations co-located with seismological instruments we were able to analyse the agreement between observations recorded with both techniques. With noise filtering technique, the positions processed in the relative and absolute Precise Point Positioning approaches were compared with seismological displacements. The comparison between GPS and SM derived displacements exhibited a Pearson’s correlation value ranging from 0.61 to 0.94 for horizontal displacements and the peak ground displacements reached 16 mm, with the accuracy of determination of approx. 2 mm for the horizontal plane and 4 mm for the vertical plane.

This is one of the first studies to analyse mining tremor using the high-rate GNSS technique, here limited to GPS data. Other studies have concerned natural earthquake analysis with HR-GNSS, and if they addressed induced shocks, it was only in the area of long-term displacements. The published research results show that also small, shallow tremors might be registered with GNSS observations, which can be supplementary in the seismological analysis.


Figure 1: Time variability of Pearson’s correlation coefficient of band-pass filtered DD displacements (left) and PPP displacements (right) in comparison with seismological data for station KOMR/LES1.

The detailed research information is presented in the paper entitled “High-rate GPS positioning for tracing anthropogenic seismic activity: The 29 January 2019 mining tremor in Legnica- Głogów Copper District, Poland” by Iwona Kudłacik (1), Jan Kapłon (1), Grzegorz Lizurek (2), Mattia Crespi (3), Grzegorz Kurpiński (4), developed in cooperation of the Institute of Geodesy and Geoinformatics Wrocław University of Environmental and Life Sciences (1), Institute of Geophysics, Polish Academy of Sciences (2), Geodesy and Geomatics Division, DICEA-Sapienza University of Rome (3) and KGHM CUPRUM Sp. z.o.o. (4). The manuscript was published in Measurement: DOI:10.1016/j.measurement.2020.108396.

This work was carried out within EPOS – the European Plate Observing System, co-financed by the European Union from the funds of the European Regional Development Fund, POIR.04.02.00-14-A0003/ 16. GNSS data was partially provided courtesy of KGHM Cuprum Sp. z. o. o. and the University of Warmia and Mazury, co-financed by the National Centre for Research and Development, POIR.04.01.04-00-0056/17.