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| Titel |
Multiplet focal mechanisms from polarities and relative locations: The Iznajar earthquake swarm (S- Spain) |
| VerfasserIn |
E. Carmona, D. Stich, G. Saccorotti, J. Ibañez |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025767
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| Zusammenfassung |
| In April 1998, a swarm of ~1800 microearthquakes near the village of Iznajar (S-Spain) was
recorded at the Granada basin short period seismic network. Focal mechanisms from P-wave
polarity readings are poorly constrained and cannot characterize the seismotectonics of the
series. Here, we propose to resolve ambiguities of first motion mechanisms by using the local
strike and dip inferred from multiplet relocation as an additional constraint on source
orientation. We use waveform cross correlation on P- and S-arrivals to identify events with
highly similar seismograms, group our detections into multiplet clusters, and invert the cross
correlation time delays to obtain precise relative locations within our largest multiplet
clusters. Relative locations have errors of several 10s of meters horizontally and vertically,
and define strike and dip of active fault patches with an accuracy of typically ~20-30Ë . We
introduce the multiplet fault plane orientations and their confidence limits to restrict the
parameter range for focal mechanism grid search, yielding mostly well-constrained
solutions, in addition resolving the nodal plane symmetry of the point source focal
mechanism. We observe mainly N-S left-lateral strike slip faulting and a few NNW-SSE
normal faulting solutions, highlighting the kinematic complexity of the swarm, and
pointing to an overall deformation style different from the nearby Granada basin. |
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