Mining-triggered seismicity governed by a fold hinge zone.
Recently, the paper dealing with mining-triggered seismic event mechanisms governed by a fold hinge zone of Bytom Syncline has appeared in the Engineering Geology.
The researchers from the Institute of Earth Science, FNS US (dr Maciej Mendecki, dr Jacek Szczygieł and prof. dr hab. Lesław Teper) and the Institute of Geophysics PAS (dr hab. Grzegorz Lizurek) studied more than forty strong mining tremor mechanisms which were observed during the mining of panel 3, Bobrek mine. The character of those atypical events and their relatively deep locations suggested that they were not a representation of typically induced seismicity associated with mining.
Comparison of geophysical, geological and tectonic studies indicated that the observed tremors are the triggered events. Usually, the accumulated stress level on natural discontinuities is not high enough to release a tremor. Mining can disturb stress distribution and lead to transfer stress from mine to deeper structures resulting in the stress level increase and triggering the seismic event. In the case of the studied area, three clusters with specific seismic events were distinguished. The first cluster represented an initial state of stress release produced by the activation of sub-vertical normal faults associated with the local fault system. Next, ahead of the Bytom Syncline Hinge, stress transfer activated all discontinuities in the rock mass. In this zone, the second cluster was indicated which was dominated by the strike-slip mechanism. The last cluster was represented by the seismic events with reverse mechanisms which occurred in the fold axis. The discussed results allowed to investigate and reveal the history of stress variation and seismicity in the studied area.
The calculations and analysis were conducted in the IS-EPOS platform using the data from Episode: BOBREK. The IS-EPOS platform is the e-tool allowing for multidisciplinary study related to the anthropogenic hazards, including mining seismicity.
The article details: https://doi.org/10.1016/j.enggeo.2020.105728
IS-EPOS web site: https://tcs.ah-epos.eu/
