Mapping Moho depth variations in central Italy from PsMoho-P delay times: Evidence of an E-W transition in the Adriatic Moho at 42°N latitude

Along the Italian peninsula adjoin two crustal domains, peri-Tyrrhenian and Adriatic, whose
boundary is not univocal in central Italy. In this area, we attempt to map the extent of the Moho in the
two terrains from variations of the travel time difference between the direct P wave and the P-to-S wave
converted at the crust-mantle boundary, called PsMoho. We use teleseismic receiver functions computed
at 38 broad-band stations in this and previous studies, and assigned each of the recording sites to the
Adriatic or peri-Tyrrhenian terrains based on station location, geologic and geophysical data and
interpretation, and consistency of delays with the regional Moho trend. The results of the present study
show that the PsMoho arrival time varies from 2.3 to 4.1 s in the peri-Tyrrhenian domain and from 3.7 to
5.5 s in the Adriatic domain. As expected, the lowest time difference is observed along the Tyrrhenian
coastline and the largest values are observed in the axial zone of the Apennine chain. A key new result of
this study is a sharp E-W boundary in the Adriatic domain that separates a deeper Moho north of about
42 N latitude from a shallower Moho to the south. This feature is constrained for a length of about 40 km
by the observations available in this study. The E-W boundary requires a revision of prior mapping of the
Moho in central Italy and supports previous hypotheses of lithosphere segmentation.