On 17 April 2015, the Wujek/Śląsk underground coal mine in Poland was struck by a strong induced tremor of magnitude M4.0. The event was followed by a massive rock burst and a collapse of tunnels in the vicinity of the hypocentre. The earthquake was widely felt in the densely populated surrounding area. In this paper, we describe a possible connection between seismological parameters, such as the seismic source location and the focal mechanism, and the ground deformation just above the collapsed tunnels a very short time after the event occurred. We have shown that joint seismological and satellite observation can be very valuable and important tools not only to improve the knowledge concerning mining rock bursts and tunnel collapses, but also to find their influences on the ground effects observed on the surface.

In rock mass disturbed by mining activity, distortions in the stress balance may lead to seismic energy being emitted in reactivated seismogenic structures. One way of increasing the imaging resolution of these seismically active structures is through relocation, which itself can be achieved using the cloud collapsing method. This method partially eliminates perturbations in the location of seismic energy sources concerning the actual positions of these sources. It enables events to be grouped into spatially ordered structures that may correspond to actual tectonic structures, such as fractures, fissures, or faults. We present the results of applying the collapsing method in mining seismology using a cloud of located events recorded during mining activity at one of the coalfaces in the Bobrek hard coal mine. The relocation procedure was applied to all the foci of events recorded during mining activity on face 3/503 between April 2009 and July 2010. In the relocated point cloud, two types of the linear structure responsible for generating events are automatically distinguished using the HDBSCAN algorithm: structures directly related to mining activity and structures associated with local tectonics. The location of the separated structures of the first type corresponds to the range of coalface 3/503 and the shafts delimiting earlier mined seams 507 and 509 located below. The isolated structures of the second type, with almost vertical orientation, are associated with existing zones of discontinuity that become seismically active as a result of mining activity. The identified structures lie near the biggest events recorded, which is evidence that these structures may correspond to real discontinuity zones.