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| Titel |
Seismicity from February 2006 to September 2007 at the Rwenzori Mountains, East African Rift: earthquake distribution, magnitudes and source mechanisms |
| VerfasserIn |
M. Lindenfeld, G. Rümpker, A. Batte, A. Schumann |
| 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 ; 3, no. 2 ; Nr. 3, no. 2 (2012-08-21), S.251-264 |
| Datensatznummer |
250000986
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| Publikation (Nr.) |
 copernicus.org/se-3-251-2012.pdf |
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| Zusammenfassung |
| We have analysed the microseismic activity within the Rwenzori Mountains
area in the western branch of the East African Rift. Seismogram recordings
from a temporary array of up to 27 stations reveal approximately 800 events
per month with local magnitudes ranging from –0.5 to 5.1. The earthquake
distribution is highly heterogeneous. The majority of located events lie
within faults zones to the east and west of the Rwenzoris with the highest
seismic activity observed in the northeastern area, where the mountains are
in contact with the rift shoulders. The hypocentral depth distribution
exhibits a pronounced peak of seismic energy release at 15 km depth. The
maximum extent of seismicity ranges from 20 to 32 km and correlates well
with Moho depths that were derived from teleseismic receiver functions. We
observe two general features: (i) beneath the rift shoulders, seismicity
extends from the surface down to ca. 30 km depth; (ii) beneath the rift
valley, seismicity is confined to depths greater than 10 km. From the
observations there is no indication for a crustal root beneath the Rwenzori
Mountains. The magnitude frequency distribution reveals a b-value of 1.1,
which is consistent with the hypothesis that part of the seismicity is
caused by magmatic processes within the crust. Fault plane solutions of 304
events were derived from P-polarities and SV/P amplitude ratios. More than
70 % of the source mechanisms exhibit pure or predominantly normal
faulting. T-axis trends are highly uniform and oriented WNW–ESE, which is
perpendicular to the rift axis and in good agreement with kinematic rift
models. At the northernmost part of the region we observe a rotation of the
T-axis trends to NEN–SWS, which may be indicative of a local perturbation of
the regional stress field. |
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