Mapping the Moho Across the Northern and Central Apennine Chain and Eastern Sicily - The Teleseismic Receiver Functions Method

Abstract

Waveforms of seismic events occurred at epicentral distances ranging from 30 to 90 , and recorded by 3-component stations installed in peninsular Italy and in eastern Sicily, were analyzed using the receiver function technique. Receiver functions are time series where the arrivals of P-to-S waves converted at marked velocity contrasts beneath a seismometer are enhanced. Teleseismic receiver functions are frequently used to identify waves converted at the Moho discontinuity to infer crustal thickness. Across the northern Apennines, receiver functions show that west of this chain (i.e. beneath the Elba island and Tuscany) the Moho is flat and shallow, while it deepens from the eastern coast of the peninsula toward the chain. Two Ps conversions are observed at a station located in the Tiberina valley, indicating the presence of the Moho at depths of about 20 and 52 km. More to the south, across the central Apennines, the Moho is shallower beneath the Tyrrhenian margin of the peninsula than beneath the Adriatic margin, and deepens from both sides toward the Apennines. The largest crustal thickness is inferred in the area of highest topography. The Moho depths estimated with the receiver function technique are in agreement with the interpretation of active seismic data in the western margin of peninsular Italy and along the Adriatic coast, while they are significantly larger beneath the Apennines. Results of an ongoing study in eastern Sicily show that Moho depth increases from north to south. In this area, the northernmost stations show a also a later Ps converted by a lower interface.