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| Titel |
Spatial variation of Lg-wave attenuation in the Iberian Peninsula |
| VerfasserIn |
Raquel Noriega, Arantza Ugalde, Antonio Villaseñor, Maria Jose Jurado |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250086293
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| Publikation (Nr.) |
 EGU/EGU2014-127.pdf |
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| Zusammenfassung |
| Within a global context, the Iberian Peninsula is a region where low to moderate (Mw < 5.5)
earthquakes occur, most of them at shallow depths (h < 40 km). Seismicity concentrates
mainly around the Pyrenean Range, the northwestern part of the peninsula, and the southern
deformation zone that includes the Betics, the Alborán Sea and the Gulf of Cádiz. In recent
years, considerable improvements in seismic data quality and geographic coverage have been
made by the deployment of new permanent and portable broadband seismic stations in
the Iberian Peninsula. The dense accumulation of seismic data has allowed us to
investigate lateral variation of crustal seismic attenuation to develop the first regional
2D Lg-wave attenuation model for the entire Iberian Peninsula and its frequency
dependence.
Seismic data used consist of 71 events with magnitudes 3 -¤ mbLg -¤ 5.4 focal depths less
than 30 km and epicentral distances from 100 to 1000 km which were recorded by 343
seismic stations between January 2008 and October 2013. To avoid confusion with
fundamental-mode Love-wave energy on the transverse components, we only analyzed
vertical component recordings.
Among all the methods proposed to measure Lg attenuation, we considered the reliable
Two-Station Method that allows removing the common source term by taking the ratio of
Lg amplitudes recorded at two different stations along the same great-circle path
from the same event. It requires, however, strict source-station configuration and
dense event and station coverage. The spectral ratios collected over high-quality
interstation paths were used to determine 1 Hz Lg Q (Q0) and its frequency dependence
η. Then, the lateral variations of the attenuation parameters were mapped using
inversion.
Lg-wave propagation was found to be inefficient or blocked for most of the paths crossing
the Mediterranean Sea, the western Alborán Sea and the Strait of Gibraltar. Our results reflect
large variations in Q0 values across the Iberian Peninsula which is in accordance with the
different geotectonic characteristics present in the region. Low Lg Q0 values (high
attenuation) were found in the Pyrenean Range and in the southern area whereas the most
stable western part of Iberia showed high Lg Q0. The obtained Lg η spatial variation
map show that intermediate η values characterize most of the analyzed region. |
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