# ETAS Space-Time Modeling of Chile Triggered Seismicity Using Covariates: Some Preliminary Results
## 2 Description of the Datasets
### The Seismic Catalog and Chilean Seismicity  
The Chilean catalog has been provided by the Chilean National Seismological Center of the University of Chile ([[http://sismologia.cl](http://sismologia.cl)]([http://sismologia.cl](http://sismologia.cl)) (accessed on 10 February 2021)). It contains the ordinary seismic variables, such as latitude, longitude, magnitude (on the Richter scale), depth, and time of occurrence of each seismic event (year, month, day, hour, minute, and seconds). From Figure 1, it is observed that the largest number of seismic events occurred in the years 2010, 2014, and 2015, which coincide with the occurrence of the highest magnitude earthquakes, of magnitudes 8.8, 8.2 and 8.4 on the Richter scale, respectively. The relationship between month and magnitude is explicitly represented in Figure 2. From this figure it is also observed that the original seismic data are normally collected with a threshold in the minimum magnitudes, since very low magnitudes are difficult to be detected. Some summary statistics, related to the historical seismic activities in Chile in the last 21 years, are reported in Table 1. This table shows that 2010 has the maximum number of events (second column) and the maximum magnitude (third column) as well. In the years 2000 and 2011, two seismic events, with the maximum magnitude in two different spatio-temporal locations, occurred. Since the seismicity has a different behavior along the coast of Chile, due to the different velocity that the Nazca Plate (Figure 3, left panel) is being subducted beneath South America (see, [22]), we considered two distinct areas (see Figure 3, right panel). In addition, the considered areas include the major earthquakes of the last 30 years. The Northern area includes the M8.2 Iquique earthquake (2 April 2014) and the second area includes the 2010 Chile earthquake of 8.8 magnitude occurred off the coast of central Chile on Saturday, 27 February 2010, which provoked a rupture of more than 1000 km length, and the M8.4 Coquimbo earthquake occurred on 16 September 2015. We consider only events with depths less than 70 km in both areas (Figures 4 and 5). Earthquakes deeper than 70 km, which occur within the subducted oceanic lithosphere [8], are excluded in our analysis for both areas. The reason is that the largest earthquakes occur at shallow depths down to 50 km and near the limit of the intermediate-depth seismic segment at 60-70 km [1], beneath the forearc section of the convergent margin. Additionally, most seismic events in Chile occur at depths between 30 and 40 km (Figures 4 and 5). These are mainly due to the deformations generated by the convergence between the Nazca Plate and the continental plate. These deformations caused the rise of the Andes Mountains, and they can reach magnitudes greater than 7 [22]. Figure 1: Distribution of number of events by month in Chile. Figure 2: Magnitude distribution by month; the green lines are the monthly minima and maxima, the red lines are the first and third monthly quartiles, while the black line is the monthly median. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Year** & **n.Events** & **Max Magn.** & **Lat.** & **Lon** & **Date** \\  & & & & **of the Yearly Largest Events** & \\ \hline
2000 & 648 & 5.0 & \(-\)29.79 & \(-\)72.08 & 2000-02-21 \\  & & & \(-\)32.68 & \(-\)71.88 & 2000-03-26 \\  
\hline \hline \end{tabular}
\end{table} 
Table 1: Summary statistics of the Chilean seismic events from 2000 to 2020. Figure 3: Left panel: Satellite image of the Southern America, with the evidence of the borders of Chile (in blue) and the tectonic plates (in gray); right panel: seismic events occurred in Chile from 2000 to 2020 in the two studied areas; in green, events in the Northern area and in red, events in the Southern area.