The effects of the local soil conditions on earthquake shaking are of ten quantified via an amplification factor, which is defined as the ratio of the ground motion at the soil surface to the ground motion at a rock site at the same location. Site amplification models are empirical equations that predict site amplification based on the general characteristics of the site. Most of the current site amplification models predict amplification based on the average shear wave velocity in the top 30 m (V S30 ). However, additional site parameters influence site amplification and should be included in site amplification models.
To identify site parameters beyond V S30 that influence site amplification and to develop an empirical site amplification model that includ es these parameters, site response analyses are performed for a large suite of shear wave velocity profiles. These analyses identified the parameter V ratio , defined as the ratio of the average shear wave velocity from 20 m and 30 m to the average shear wave velocity in the top 10 m, as an important site parameter that influences site amplification. An empirical site amplification model is developed based on the site response results that predicts amplification as a function of V s30, V ratio, spectral acceleration on rock, and depth to rock.
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