Soil Seismic Non-Linear Behavior Inferred by Analysis of Vertical Arrays Recordings

Date: 4/26/2019

Time: 02:00 PM

Room: Pine

Seismic ground motion is strongly dependent on the subsurface layers mechanical characteristics and geometry. This phenomenon must be considered in hazard assessment through the evaluation of the seismic soil response. This response is not only depending on the soil parameters but also on the level of the seismic solicitation. The non-linear behavior is especially important to consider when modeling strong ground motion. We analyzed this effect using seismological data recorded by the Japanese Kiban Kyoshin Network (Kik-net). We use recordings from boreholes instrumented with two 3-components accelerometers, one located at surface and the other in depth. From these data, we are estimating the transfer functions by the computation of borehole spectral ratios (BSR) and are taking the advantage of the large database to study the variability of theseBSRwith the level of seismic solicitation.

The main effect of the soil non-linear behavior on the transfer function is a shift of the amplification peaks towards lower frequencies and a decrease of the amplification level. We propose thus to characterize this non-linear behavior by quantifying those changes in the BSR. This work results in site-dependent relationships between the intensity of the ground motion and the modifications in the BSR. The presentation will show the procedure used for correcting surface ground motion of the non-linear behavior of the soil. The results obtained on several cases demonstrates that this procedure better predict strong motion and thus an attempt to take it into account in semi-empirical ground motion prediction is presented.

Presenting Author: Etienne Bertrand

Authors