BUSCADOR RECOLECTA

EVENT-SHELF Cruise (29GD20080906) carried out on the Research Vessel García del Cid in 2008, Integration of new technologies in paleosismology: General aims:Characterization of seismogenic and tsunamigenic faults in South Iberia.a) to characterize the seismic potential of the Eastern Betics Shear Zone; 2) to adapt the paleoseismological methodology to the analysis of slow moving faults,and 3) training young researchers in onshore-offshore paleoseismology. Specific works: To achieve the main objectives of the EVENT-SHELF cruise in the Eastern Betics Shear Zone (EBSZ) area, we carried out a geophysical exploration (swath bathymetry, acoustic backscatter and high-resolution single-channel sparker seismics) of the Adra/Carboneras, Palomares and Bajo Segura fault zones on the shelf areas. During the cruise we have adapted high resolution- low penetration geophysics to the paleoseismological analysis of the EBSZ fault terminations located on the continental shelf, often difficult to image with conventional low-resolution systems. Major destructive events occurred in some of the areas investigated during the cruise, such as the 1522 Almería (EMS IX Intensity), the 1829 Torrevieja (EMS X Intensity) and the 1910 Adra earthquakes (EMS VIII Intensity) (IGN, 2005). Most of the acquired profiles were oriented perpendicular to the fault orientation and other few profiles were acquired to explore the structure of deep-coral mounds in the Chella Bank [11]. Moreover, ROV and towed camera transects were carried out along some of the coral-mound to obtain visual groundtruthing of the acoustic data. Methods The following methodology was used during the EVENT-SHELF cruise: • High resolution seismics. During the EVENT-SHELF cruise we used a high-resolution single seismic system on board the B/O García del Cid able to acquire data with a 30 cm of resolution at 1.5 km depth. The source, a sparker GEO-SPARK 6kJ from GEO-RESOURCES BV (www.geo-resources.com), is specially designed to favour high frequencies . The receiver consisted on a 9 m long, 24 channel, streamer. Part of the data was processed on board with the specific software Geotrace supplied by the company. • Bathymetric survey. Simultaneously with the seismic survey, we acquired information regarding seafloor morphology (bathymetry and backscatter) with the double frequency (180-50 kHz) Elac Nautik SeaBeam 1050D available in the B/O García del Cid and managed by the Unidad de Tecnología Marina (UTM, CSIC). Only data with less than 350 m depth were acquired due to technical acquisition problems in the echo-sounder (50 kHz low frequency MB not functioning). • Visual groundtruthing. Visual inspections was carried out in the deep- coral mounds area of the Chella Bank. Video transects allowed to visualize and record seafloor images, helpful to calibrate backscatter and seismic data in areas where deep coral mounds occur, and to detect and recognize the benthic assemblages present in the seamounts of the Almería Margin. The remotely operated vehicle (ROV) SPY-ICM Mariscope (provided by ICM-CSIC) was used for the shallowest transects (100-200 m), whereas the deep towed video-camera DTS6000 Seatronics was used in the deepest mounds of the Chella Bank (200-400 m) • Sediment sampling. A 25 l Van Veen dredge was also deployed to collect sediment samples in a subaqueous dune field and in a coral rubble area identified in the Chella Bank