A càrrec de Grant G. Buffet (Institut de Ciències de la Terra Jaume Almera - CSIC)
Seminaris de la Facultat de Geologia i l'Institut de Ciències de la Terra Jaume Almera

Universitat de Barcelona (UB)
Consell Superior d'Investigacions Científiques (CSIC)

Dia: dimecres 24 de març
Hora: 12.00 h
Lloc: sala d'actes de l'Institut Jaume Almera

Resum:
Seismic reflection profiling is an active source technique that has been used for decades to create detailed maps of the subsurface. It has been widely employed to image hydrocarbon traps, study plate tectonic processes, image the crust-mantle boundary or for other purely scientific endeavors. Seismic surveys over the oceans have also invariably recorded the comparably minute reflections from within the water column itself, having been largely ignored until recently. Indeed, the whole water column was generally considered 'noise' by seismologists in search of oil and gas or for an understanding of the interior workings of the Earth and was muted from the data before further analysis.

Of late, amidst the growing rhetoric of climate change, seismologists have realized the value of analyzing water column reflections for the information they contain about thermohaline finestructure. Whereas, in the solid earth, acoustic impedance contrasts are brought about by differences in lithology, in the oceans, variations of temperature and salinity are the cause. In this way, seismic reflection profiling can be used to map oceanic thermohaline finestructure with a horizontal resolution of about 10 m, some two orders of magnitude finer than traditional in-situ probing. The major advantage of seismic oceanography is in terms of flow visualization as it allows finestructure to be continuously mapped over hundreds of kilometers, creating a picture of large scale circulation in the oceans. It therefore has important implications for the understanding of the redistribution of the planet's heat and its consequential effect on climate.

I present results from analysis of seismic data in the coastal waters of the Iberian peninsula. Specifically, the variation in seismic amplitude downstream of the Mediterranean Undercurrent is presented as a proxy for temperature, oceanic finestructure scale lengths are remotely extracted through stochastic heterogeneity mapping and a video of moving seismic reflectivity shows internal wave fluctuations on a time scale of minutes.