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| Titel |
Indications for different types of brittle failure due to active coal mining using waveform similarities of induced seismic events |
| VerfasserIn |
S. Wehling-Benatelli, D. Becker, M. Bischoff, W. Friederich, T. Meier |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 4, no. 2 ; Nr. 4, no. 2 (2013-10-31), S.405-422 |
| Datensatznummer |
250084942
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| Publikation (Nr.) |
 copernicus.org/se-4-405-2013.pdf |
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| Zusammenfassung |
Longwall mining activity in the Ruhr coal mining district leads to
mining-induced seismicity. For detailed studies the seismicity of a single
longwall panel beneath the town of Hamm-Herringen in the eastern Ruhr area
was monitored between June 2006 and July 2007 with a dense temporary network
of 15 seismic stations. More than 7000 seismic events with magnitudes between
–1.7 ≤ ML ≤ 2.0 were detected and localized in this period.
Most of the events occurred in the vicinity of the moving longwall face.
In order to find possible differences in the brittle failure types of these
events an association of the events to distinct clusters is performed based
on their waveform characteristics. This task is carried out using a new
clustering algorithm utilizing a network similarity matrix which is created
by combining all available 3-component single station similarity matrices.
The resultant network matrix is then sorted with respect to the similarity of
its rows leading to a sorted matrix immediately indicating the clustering of
the event catalogue. Finally, clusters of similar events are extracted by
visual inspection.
This approach results in the identification of several large clusters which
are distinct with respect to their spatial and temporal characteristics as
well as their frequency magnitude distributions. Comparable clusters are also
found with a conventional single linkage approach, however, the new routine
seems to be able to associate more events to specific clusters without
merging the clusters.
The nine largest observed clusters can be tentatively divided into three
different groups that indicate different types of brittle failure. The first
group consists of the two largest clusters which constitute more than half of
all recorded events. Results of a relative relocation using cross-correlation
data suggest that these events are confined to the extent of the mined out
longwall and cluster close to the edges of the active longwall at the depth
of active mining. These events occur in lockstep with the longwall advance
and exhibit a high b value of the Gutenberg–Richter relation (GR) of about
1.5 to 2.5 and consist of small magnitude events. Thus, these events
represent the immediate energy release adjacent to the mined out area.
The second group consists of clusters located either slightly above or below
the depth of active mining and occurring at the current position of the
longwall face within the confines of the longwall. They consist of generally
stronger events and do not follow GR. This activity might be linked to the
failure of more competent layers above and below the mined out seam resulting
in larger magnitude events.
Finally, one cluster represents seismic activity with a rather low b value
below 1 and events located partly towards the north of the longwall which
are delayed with respect to the advance of the longwall face. These events
are interpreted as brittle failure on pre-existing tectonic structures
reactivated by the mining activity. |
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