EMPHASIZING THE RECENT TECTONIC ACTIVITY OF BLIND THRUSTS USING NATURAL SEISMIC NOISE: THE CASE OF THE FERRARA ARC,ITALY

摘要

During the seismic crisis of May-June 2012,that strongly affected the central sector of the Ferrara Arc(Italy),relevant coseismic effects were observed,such as ground deformations and amplification phenomena due to the low quality of the mechanical characteristics in the shallow subsurface(i.e.few hundreds of meters).We exploited seismic noise-based strategies as a low cost tool to gain insight on the subsurface.We carried out several single-station and array measurements(i.e.ESAC,ReMi,and HVSR),across some of the major tectonic structures of the eastern Po Plain,belonging to the most advanced buried sector of the Northern Apennines,the”Ferrara Arc”.Such investigations were performed along two profiles,about 27 km-long,almost perpendicular to the regional trend of the structures.Our results clearly document lateral shear wave velocity variations and the occurrence of resonance phenomena between 0.52 and 0.85 Hz.Additionally,we were able to infer the depth of the resonant interface(s)and to associate them with the major known stratigraphic discontinuities,thus emphasizing effects connected to the recent tectonic activity of the blind thrusts affecting this sector of the Ferrara Arc.