Seismic Ambient Noise Characterization of a New Permanent Broadband Ocean Bottom Seismometer Site offshore Catalonia (Northeastern Iberian Peninsula)

The scientific importance of long-term ocean-floor seismic observatories has been widely and internationally recognized by earth science communities. In addition to their usefulness in investigating global-scale geophysical processes, long-term ocean-floor observations are also required to better constrain regional tectonics. However, the implementation of ocean-floor seismic stations is a difficult task, and efforts have been made for more than two decades to resolve the technological and logistical issues associated with such deployments (Romanowicz et al. 2009; Suyehiro et al. 2006). Different programs in the United States and Canada ( e.g. , NEPTUNE Project, http://www.neptune.washington.edu), Japan ( e.g. , ARENA Project, Massion et al. (2004).), and in Europe ( e.g. , ESONET Project, http://www.oceanlab.abdn.ac.uk/research/esonet.php) have promoted ocean-floor observatories, most of them multidisciplinary. A review of seafloor observatory science can be found in Favali and Beranzoli (2006). The first initiative for long-term seafloor seismic monitoring in Spain was successfully realized on August 12, 2005, when a permanent broadband ocean-bottom seismometer (OBS) and a differential pressure gauge (DPG) were installed at about 50 km offshore of the region of Catalonia in the northeastern Iberian Peninsula (Figure 1). The ocean-floor station was completely integrated into the Catalan Seismic Network (CSN) in October 2007, when satellite transmission made it possible to have continuous and real-time data available at the network data center in Barcelona. The station, with geographical coordinates 40.71°N and 1.36°E, has the code COBS at the International Registry of Seismograph Stations of the International Seismological Centre. The project was initially designed with the main goal of improving the understanding of the seismicity of the surrounding region, which is densely populated and industrially very active. The presence of nuclear power plants and chemical and oil industry facilities in the area has major implications on the seismic risk assessment of the region. Moreover, the fact that some …