Crustal structure at colliding plates boundary from receiver functions analysis: A close look beneath the northern Apennines (Italy)

Abstract

Teleseismic receiver functions from a seismic experiment in a small area of the northern Apennines, Italy, reveal strong crustal structure variations across the mountain chain. Receiver functions imaging and full waveform inversion technique are used to constrain the S‐wave velocity profile in the crust and to reconstruct the geometry of the main seismic discontinuities at depth. We highlight the presence of the main mode‐converting discontinuities in the study area. Most importantly, we identify the crust‐mantle transition which is represented, almost everywhere in the study area, by a sharp S‐wave velocity increase (over 4 km/s) at depth between 35 and 40 km. However, farther west, the S‐wave velocity reaches values typical for the sub‐crustal mantle at about 54 km depth, possibly marking the locus where the subducting Adriatic plate starts to dip into the mantle. Here the presence of a shallower discontinuity at about 36 km depth, with S‐velocity values around 4 km/s, can be interpreted as the Moho signature of the overriding Tyrrhenian plate.