Ground motion prediction equations for the Chilean subduction zone

Abstract

The Chilean subduction zone is one of the most active in the world. Six events of magnitude greater than Mw= 7.5 have occurred in the last 10 years, including the 2010 Mw= 8.8 Maule, the 2014 Mw= 8.2 Iquique, and the 2015 Mw= 8.3 Illapel earthquakes. These events have produced a considerable dataset to study interface thrust and intraslab intermediate depth earthquakes. In this paper, we present a database of strong motion records for Chilean subduction zone earthquakes and develop a ground motion prediction equation (GMPE) for peak ground acceleration and response spectral accelerations with 5% damping ratio for periods between 0.01 and 10 s. The dynamic soil amplification effects are considered in a new empirical model based on two parameters, the predominant period of the soil (T∗) and the average shear wave velocity down to 30 m depth (VS30). The spectral accelerations prediction equations at short periods are generated using 114 records of intraslab earthquakes (Mw = 5.5–7.8) and 369 records of interface earthquakes (Mw = 5.5–8.8); a reduced number of these records are used for longer periods. The proposed GMPE can predict the ground motion of large Chilean subduction earthquakes (Mw> 8) with no need of extrapolation from small-magnitude earthquake data. Intraslab earthquakes show a steeper attenuation slope than that of interface ones, which is consistent with other GMPE results derived from worldwide subduction zones data. Moreover, the Chilean interface earthquakes show a flatter attenuation slope relative to the Japanese ones.