Moho Depth in Peninsular Italy From Teleseismic Receiver Functions

We analyzed teleseismic data recorded in the past 4 years by the Italian National Seismic Network and MedNet to retrieve the Moho depth beneath Italy. To improve coverage in areas where the sampling is low, we added data recorded by temporary experiments carried out in the region during the last few years (i.e. Retreat, CatScan, and others). Our data-set comprises more than 8,000 teleseismic waveforms recorded at 165 broad-band stations. The stations were classified in five quality categories, according to the sharpness of the Ps converted phases and to the presence and continuity of multiple phases. We extracted first-order information about the crustal properties (i.e. Moho depth and Vp/Vs ratio) using the technique developed by Zhu and Kanamori (2000). We modified the original stacking method using three different crustal Vp values. Also, the definition of the quality level for each single station has been used to weight the stacking result. A first idea on the Moho geometry beneath the Italian peninsula comes from the distribution of the stations as a function of the quality level. The stations deployed along the Tyrrhenian side of peninsular Italy and above the Apulian platform are characterized by high quality ranking, while medium- to low-quality data can be found everywhere along the Apennines. Data-set coming from the Southern Apennines and the Calabrian arc display very low quality. The main reason for the decreased data quality in these areas is the presence of sharp velocity discontinuities at shallow depth, such as the Apulian carbonate platform below the Apenninic allochtonous cover in the southern Apennines, or the complex upper crustal structure in the Calabrian arc. In the regions of simple crustal structure, corresponding to high quality ranking, the technique allows to determine clearly the Moho depth and the mean Vp/Vs value in the crust: in the peri-Tyrrhenian region the crust is as thin as 20 km; in the Apulia foreland region we find a thicker crust (30-35 km); finally, the Apenninic belt exhibits highly variable values of crustal thichness, generally between 35 and 40 km. Other regions along peninsular Italy show a complex pattern, and a unique clear Moho is not easily identified.