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 \(M_w = 7.5\) have occurred in the last 10 years, including the 2010 \(M_w = 8.8\) Maule, the 2014 \(M_w = 8.2\) Iquique, and the 2015 \(M_w = 8.3\) 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 (\(V_{S30}\)). The spectral accelerations prediction equations at short periods are generated using 114 records of intraslab earthquakes (\(M_w\) = 5.5–7.8) and 369 records of interface earthquakes (\(M_w\) = 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 (\(M_w > 8\)) 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.