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Structural control on the directional amplification of seismic noise (Campo Imperatore, central Italy)
Author(s)
Language
English
Obiettivo Specifico
4T. Sismologia, geofisica e geologia per l'ingegneria sismica
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/471 (2017)
Pages (printed)
10-18
Issued date
2017
Abstract
Seismic signals propagating across a fault may yield information on the internal structure of the fault zone. Here we have assessed the amplification of seismic noise (i.e., ambient vibrations generated by natural or anthropogenic disturbances) across the Vado di Corno Fault (Campo Imperatore, central Italy). The fault zone is considered as an exhumed analogue of the normal faults activated during the L'Aquila 2009 earthquake sequence. Detailed structural geological survey of the footwall block revealed that the fault zone is highly anisotropic and is affected by a complex network of faults and fractures with dominant WNW–ESE strike. We measured seismic noise with portable seismometers along a ∼500 m long transect perpendicular to the average fault strike. Seismic signals were processed calculating the horizontal-to-vertical spectral ratios and performing wavefield polarization analyses. We found a predominant NE–SW to NNE–SSW (i.e., ca. perpendicular to the average strike of the fault-fracture network) amplification of the horizontal component of the seismic waves. Numerical simulations of earthquake-induced ground motions ruled out the role of topography in controlling the polarization and the amplitude of the waves. Therefore, the higher seismic noise amplitude observed in the fault-perpendicular direction was related to the measured fracture network and the resulting stiffness anisotropy of the rock mass. These observations open new perspectives in using measures of ambient seismic noise, which are fast and inexpensive, to estimate the dominant orientation of fracture networks within fault zones.
Type
article
File(s)
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Name
Earth and Planetary Science Letters 2017 Pischiutta.pdf
Size
2.55 MB
Format
Adobe PDF
Checksum (MD5)
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