Characterization of the earthquake differential ground-motion in the near field

Title : Characterization of the earthquake differential ground-motion in the near field

Laboratory : ISTerre

Supervisors : Cécile CORNOU
Mathieu CAUSSE

Phone : 04.76.63.51.73

Key words : seismic hazard, earthquake ground-motion modeling.

Objectives :

Predicting earthquake ground-motion is fundamental to design structures and estimate potential damages. Ground-motion is classically defined in terms of translational motion. Nevertheless it has long been recognized that the small-scale spatial variability of ground-motion (differential ground-motion and spatial variability at a few tens of meter scale) can induce significant structural damage due to torsional and rocking effects, and hereafter affect extended lifelines such as bridges and pipelines. Such spatial variability results from different contributions : wave passage effects, spatial soil heterogeneity, waves scattering and seismic rupture mechanism. The data collected so far at dense array sites is however still to sparse to provide in-depth understanding and accurate estimates of the spatial variability, especially in the near-field.
This work will aim to better quantify the small-scale spatial variability of near-fault ground-motion and to capture the underlying main physical mechanisms by means of ground motion modeling at dense arrays surrounding the fault. Especially the source contribution (source mechanism, source heterogeneity and directivity effects) will be carefully investigated. Numerical simulations will be mainly based on the 2003 Bam (Iran) earthquake (M = 6.6) so as to get realistic estimates of the ground-motion spatial variability. This earthquake is a typical example of a strike slip event that was recorded in the city center, which was massively destroyed.