Vertical ground motion model for PGA and spectral accelerations for the Chilean subduction zone

We present a ground motion model for computing medians and standard deviations of peak ground accelerations and 5%-damped spectral accelerations for vibration periods between 0.05s and 10s in the vertical component within the Chilean subduction zone. The model is derived from a database of 4760 ground motion records obtained by 300 strong-motion stations during 3595 interface and 1165 inslab events. This database includes records of megathrust earthquakes such as the M _w 8.8 2010 Maule Earthquake, the M _w 8.2 2014 Iquique Earthquake, and the M _w 8.4 2015 Illapel Earthquake. Median values are computed as a function of the type of event (interface or inslab), moment magnitude, focal depth, source-to-site distance, and the time-averaged shear wave velocity in the upper 30 m of the site. The resulting standard deviation is similar to those of previously developed models for horizontal 5%-damped spectral accelerations within the Chilean subduction zone. Using the proposed model for the vertical component and previous models for the horizontal component, the median vertical-to-horizontal ratio varies between 0.4 and 0.9, depending on the period.