Determination of Moho depth and dip beneath MEDNET station AQU by analysis of broadband receiver functions

Abstract

We applied the receiver function technique to retrieve Moho depth and dip beneath the MEDNET very-broadband seismographic station at l'Aquila, in the Central Apennines. Broadband data available for teleseismic events recorded in two years of operation were sufficient to delineate a rather simple structure consisting of a 32-34 km thick crust, in agreement with previous studies based on refraction seismics. In addition, the data show relatively large variation in the amplitude of the converted P-to-S phase generated at the crust-mantle interface as a function of azimuth. These variations are consistent with synthetic receiver functions generated for an incident P wave interacting with an interface dipping ~ 8° to the north. Observations of amplitude ratios of converted phases, polarity of first-motion in the SH directíon, and relative travel time delay are all consistent with a model assuming a Moho discontinuity about 33 km deep gently dipping towards north. The receiver function technique has shown to be an efficient tool for investigating deep crustal structure, giving localized but reliable information.