Cavola experiment site: geophysical investigations and deployment of a dense seismic array on a landslide

Abstract

Geophysical site investigations have been performed in association with deployment of a dense array of 95 3-component seismometers on the Cavola landslide in the Northern Apennines. The aim of the array is to study propagation of seismic waves in the heterogeneous medium through comparison of observation and modelling. The small-aperture array (130 m×56 m) operated continuously for three months in 2004. Cavola landslide consists of a clay body sliding over mudstone-shale basement, and has a record of historical activity, including destruction of a small village in 1960. The site investigations include down-hole logging of P-and S-wave travel times at a new borehole drilled within the array, two seismic refraction lines with both P-wave profiling and surface-wave analyses, geo-electrical profiles and seismic noise measurements. From the different approaches a consistent picture of the depths and seismic velocities for the landslide has emerged. Their estimates agree with resonance frequencies of seismic noise, and also with the logged depths to basement of 25 m at a new borehole and of 44 m at a pre-existing borehole. Velocities for S waves increase with depth, from 230 m/s at the surface to 625 m/s in basement immediately below the landslide.

Investigating the Influence of a Pre-Existing Shear Band on the Seismic Response of Ideal Step-like Slopes Subjected to Weak Motions: Preliminary Results

“…Therefore, the propagation of seismic waves into a slope could be potentially affected by the presence of a weakened shear band, which may modify the response at the ground surface even during weak earthquake motions. Furthermore, some studies have shown the characteristic directivity of the slope dynamic response to seismic shaking on the basis of geological, geophysical and in situ investigations (e.g., [51][52][53][54][55]). Moreover, a sloping surface can generate a parasitic vertical component of acceleration even for input motions characterised by horizontally polarised waves due to the reflection of the incoming waves from the inclined slope surface [19,56].…”