Crustal study of the pyrenees by refraction and wide-angle reflection using earthquakes as a natural seismic source

Abstract

In this study we analyse three wide-angle seismic profiles in the Pyrenees to provide new insights into their crustal structure. Several earthquakes with magnitudes greater than 2.5 that occurred in the vicinity of the analysed profiles have been used as the seismic source. We demonstrate the feasibility of using natural seismicity as the seismic source, which would allow using deployments of seismic stations designed for other objectives. We have analysed a total of three profiles in this study, two of them being located in the eastern Pyrenees (Cataluña) with N-S and E-O directions, and the third in the western Pyrenees (Navarra) with NE-SO orientation. All of them were originally deployed to record teleseisms for receiver function analysis. Profiles in the eastern Pyrenean edge constrain the top of the lower crust at a depth of 20 km. In the easternmost sector of the E-W profile, Moho has been imaged as an eastward rising ramp, with a depth decreasing from 35-40 km in the middle of the profile to a depth of 25 km in the eastern edge. The Navarra profile allowed us to constrain the crustal structure of the western Pyrenean edge in detail. The obtained model allowed the imaging of the mid-lower crustal indentation between the Iberian and European plates. The European Moho has been constrained at a depth of 30 km in a small region of the central part of the model, whereas the Iberian Moho has been imaged in its northernmost edge dipping northwards to a depth of 45-50 km.