Collapsing method for detailed recognition of seismogenic structures
activated during underground mining.
Abstract
In rock mass disturbed by mining activity, distortions in the stress
balance may lead to seismic energy being emitted in rejuvenated
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 phenomena
to be grouped into spatially ordered structures that can correspond to
actual tectonic structures, such as fractures, fissures or faults. The
article presents results of applying the collapsing method in mining
seismology using cloud of tremors 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 tremors recorded during mining activity
on face 3/503 between 04.2009 and 07.2010. In the relocated point cloud
two types of linear structure responsible for generating tremors are
distinguished: 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 tremors
recorded, which is evidence that these structures may correspond to real
discontinuity zones.