HR: 0803h
AN: NS11D-0795    [Abstracts]
TI: Characterization of Active Faults in the Algarve
AU: * Carvalho, J G
EM: joao.carvalho@ineti.pt
AF: Inst. Nacional Eng. Tecn. Inovacao, Apartado 7586, Amadora, 2721-866, Portugal
AU: Ramalho, E C
EM: elsa.ramalho@ineti.pt
AF: Inst. Nacional Eng. Tecn. Inovacao, Apartado 7586, Amadora, 2721-866, Portugal
AU: Dias, R
EM: ruben.dias@ineti.pt
AF: Inst. Nacional Eng. Tecn. Inovacao, Apartado 7586, Amadora, 2721-866, Portugal
AU: Pinto, C C
EM: carlos.cancela@ineti.pt
AF: Inst. Nacional Eng. Tecn. Inovacao, Apartado 7586, Amadora, 2721-866, Portugal
AB: The Carcavai fault zone is a NE-SW trending outcropping structure extending between S. Brás de Alportel (North) and Quarteira (south), with a total length of about 20 km, presenting reverse fault geometry with left-lateral strike- slip component. It is located close to the city of Loulé, in the Algarve region, southern Portugal. The fault zone has a complex surface course with two different sectors. The northern sector is characterized by several faults with NE-SW to E-NE-E-SW segmented by NW-SE trending faults. In the southern sector, trending NE-SE, there are several evidences of neotectonic deformation in sediments of Pio-Quaternary age. It is therefore considered to be an active fault zone and a probable source of the 1856 Loulé earthquake (intensity of VIII -MM). The study of this structure is of great importance for a proper evaluation of seismic hazard of the region. The location of some sectors of the fault zone is still to be confirmed, as well as the vertical offsets of the structure. In order to estimate these parameters, segment lengths and study the geometry of the fault zone at depth, geophysical data were acquired, as well as new geological data. In areas where the location of the fault was more uncertain, EM and seismic reflection profiles with a coarse spatial sampling were carried out. After the detailed location of the fault zone, and in places where geological evidence suggested the presence of the structure, seismic reflection profiles with a tighter spatial resolution were acquired. A standard processing flow was applied to the data and the refraction interpretation of the first breaks was also performed. The integrated interpretation of the geological and geophysical data confirmed the presence of a large reverse fault zone. The total fault length is still unknown since its prolongation offshore is still being studied. Together with vertical offsets estimates obtained, this data set will allow an improvement of the seismic hazard of the area, namely providing more refined estimates of co-seismic rupture, maximum expected earthquake and return periods.
DE: 8002 Continental neotectonics (8107)
DE: 8107 Continental neotectonics (8002)
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting