2024-03-28T19:36:43Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/198722020-05-29T11:09:37Zcom_10261_82com_10261_8col_10261_335
urn:hdl:10261/19872
Seismicity analysis at the Prestige oil-tanker wreck area (Galicia Margin, NW of Iberia)
Diaz, J.
Gallart Muset, Josep
Gaspà Rebull, Oriol
Córdoba, Diego
Regional seismicity
Galicia Margin
NW Iberia
OBS and land seismic networks
Local seismicity
Seismic pulses and harmonic tremors
An evaluation of the geological hazard related to the sinking of the Prestige oil-tanker in November 2002 in the Galicia margin,
NW of Iberia, was supported by the Spanish research agency. It included a specific seismic study of the local activity and of the
regional seismicity in this margin, results of which are presented here. Published global catalogues show that diffuse seismicity of
moderate magnitude (events up to 5.6 mb) can be associated with the Northern flank of the Galicia Margin, with a roughly E–W
distribution. However, event locations in this area are poorly constrained due to the inappropriate geometry of permanent seismic
networks. We collected and analyzed new data from a dense deployment of 10 OBS around the wreck site and from a network of
12 land stations at the NW corner of Iberia. During a 7 months operation period, the land network permitted location of 120 events
with magnitudes ranging from 1.6 to 4.8, more than 30% of which were not reported by the Spanish permanent array, confirming
the existence of a moderate seismicity in this area. Five new focal solutions have been obtained for events on-land, providing
additional information about the active faults in the region. The OBS network ran for 1 month and allowed the location of three
earthquakes of magnitude≤2.5 near the sinking site. Four more events have been identified, with just a rough determination of
their epicenters based on polarization of the P-wave arrivals. Besides these earthquakes, the OBS data recorded numerous seismic
events of different types. They include: i) groups of very short and regularly spaced pulses that can be explained as acoustic calls
generated by finback whales; ii) a large number of short-duration seismic events (2–3 s long) identified only at individual OBS;
iii) local intense monochromatic signals lasting for up to 4 h that can be described as harmonic tremors. These last two types of
seismic events might be related to hydrothermal activity within the uppermost sediments and deserve additional studies to
appropriately establish the seismic hazard of this area.
2008-03
artículo
Marine Geology 249(1-2): 150-165(2008)
0025-3227
10261/19872
10.1016/j.margeo.2007.09.015
eng
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