  We propose a critical analysis of the moment tensor solutions of the major
seismic events that affected northern Italy in 2012. Inverting full waveforms
at regional distance using the non-linear method named INPAR, we investigate
period dependent resolution that affects in particular the solutions of shallow
events. This is mainly due to the poor resolution of Mzx and Mzy components of
the seismic tensor when inverting signals whose wavelengths significantly
exceed the source depth. As a consequence, instability affects both source
depth and fault plane solution retrieval, and spurious large Compensated Linear
Vector Dipole components arise. The inversion performed at cutoff periods
shorter than 20 s reveals in many cases different details of the rupture
process, that are not resolved inverting at longer cutoff periods. Thus we
conclude that inversion of full waveforms at cutoff period as short as possible
should be preferred.
