A preliminary catalog of moment tensors for the Pyrenees

Using waveform data gathered from the different organizations that operate seismological networks in the Pyrenees, we have obtained a complete moment tensor catalog of Pyrenean earthquakes with magnitude larger than 3 covering the time period 2001–2011. Our moment tensor solutions are in good agreement with those previously reported by other institutions. We find absolutely no evidence for inverse faulting in the Pyrenees. On the opposite, almost all the events have extensional focal mechanisms, while only one event has a clear strike-slip mechanism. The T axes are consistently oriented along a NNE–SSW direction, giving further support for a currently active extensional regime of deformation in the Pyrenees. The scaling relation between moment magnitude and local magnitude has a slope close to unity. In contrast, the scaling between our moment magnitudes obtained by waveform inversion and the moment magnitudes determined by inversion of shear wave spectra from Drouet et al. (2010) has a slope of 1.31. Further work is thus required to identify the source of this discrepancy and to define a robust magnitude scale for the quantification of earthquakes in the Pyrenees.

► We report a moment tensor catalog for Mw > 3 events in the Pyrenees from 2001 to 2011.
► Focal mechanisms suggest a predominant extensional regime.
► The main direction of extension is perpendicular to the strike of the Pyrenean range.