EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Evaluation of the effect of depth to bedrock on seismic amplification phenomena

gaetano falcone1, giuseppe naso2, stefania fabozzi1, federico mori1, massimiliano moscatelli1, edoardo peronace1, and gino romagnoli1
gaetano falcone et al.
  • 1Istituto di Geologia Ambientale e Geoingegneria, Consiglio Nazionale delle Ricerche, Roma, Italy (,,,,, gino
  • 2Dipartimento della Protezione Civile, Roma, Italy (

When an earthquake occurs, the propagation of the seismic waves is conditioned by local conditions, e.g., depth to seismic bedrock and impedance ratio between soft soil and seismic bedrock. Bearing in mind that the maximum depth of site prospections generally does not extend up to seismic bedrock depth, a parametric study was carried out with reference to ideal case studies in order to investigate the effect on local seismic amplification of the depth to bedrock.

The results are presented in terms of charts of amplification factors (i.e., ratio of integral quantities referred to free-field and reference response spectra) and minimum depth to investigate vs building type. These charts will allow defining the thickness of the cover deposit that should be characterised in terms of geophysical and geotechnical parameters in order to perform seismic site response analysis according to a precautionary approach, in areas where depth to seismic bedrock is higher than conventional maximum depth of site surveys.

How to cite: falcone, G., naso, G., fabozzi, S., mori, F., moscatelli, M., peronace, E., and romagnoli, G.: Evaluation of the effect of depth to bedrock on seismic amplification phenomena, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5848,, 2020

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Presentation version 1 – uploaded on 26 Apr 2020
  • CC1: Comment on EGU2020-5848, Hans-Balder Havenith, 03 May 2020

    Dear Gaetano,

    a simple rule .. for designing seismic prospection applied to site effect analysis could be ..

    first shallow seismics are completed to see which is the near surface Vs (or Vs30) level ...100m/s ... 500m/s ...

    and the higher Vs in the near surface layers .. the deeper should be the prospection target.

    This is actually the rule that we generally apply as relevant resonance frequencies (0.5-5 Hz) are dependent on the VS/H ratio (exactly Vs/4h).

    Very low Vs (100 m/s)  .. will produce resonance frequencies only above 0.5 Hz .. if the depth is less than 50 m. (easy to be reached with seismics) .. while for Vs of 500 m/s .. 250 m need to be reached... that's more or less what you show, no?

    ..for the chat.