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| Titel |
Cluster analysis and relative relocation of mining-induced seismicity using HAMNET data |
| VerfasserIn |
S. Wehling-Benatelli, D. Becker, M. Bischoff, W. Friederich, T. Meier |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250070434
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| Zusammenfassung |
| Longwall mining activity in the Ruhr-coal mining district leads to mining-induced seismicity.
For detailed studies seismicity of the single longwall panel S 109 beneath Hamm-Herringen
in the eastern Ruhr area was monitored between June 2006 and July 2007. More than 7000
seismic events with magnitudes -1.7 -¤ ML -¤ 2.0 are localized in this period.
70% of the events occur in the vicinity of the moving longwall face. Moreover,
the seismicity pattern shows spatial clustering of events in distances up to 500 m
from the panel which is related to remnant pillars of old workings and tectonic
features.
Two sources with common location and rock failure mechanism are expected to
show identical waveforms. Hence, similar waveforms suggest similarity of source
properties. Waveform similarity can be quantified by cross-correlation. Similarity
matrices have been established and build the basis of a cluster analysis presented
here.
We compare two approaches for cluster definition: a single-linkage approach and
excerpting clusters by visual inspection of the sorted similarity matrices. Clusters are found
as areas of high inter-event similarity in the depicted matrix. In contrast, the single-linkage
approach assigns an event to the cluster if the similarity threshold Ïsl = 0.9 is exceeded to at
least one other member. This method is more restrictive and, in general, leads to clusters with
less members than visual inspection.
Both methods exhibit clusters which show the same properties. The largest clusters are
built by low-magnitude events (around ML --0.6) directly at the longwall face at the
mining level. Other clusters include events with magnitudes as large as ML,max = 1.8. Their
locations tend to lie above or below the mining level in load-bearing sandstone layers. Mining
accompanying events show face-parallel near vertical fault planes whereas more
distant clusters have typical solutions of remnant pillar failure with a medium dip
angle.
Relative relocation of the events is done using lag times from the cross-correlation
procedure. The relative location accuracy within the clusters is increased to some meters. We
find that most of the seismicity within the longwall panel concentrates on two narrow bands. |
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