## 3 Methodology
### Tsunami Propagation and Simulation Assessment  
The town of Chafaral has an official tsunami inundation map [44]. For the elaboration of this map, a deterministic approach with an extreme event of magnitude Mw 8.6 was considered. This was based on a combination of two past earthquakes, namely the events of 1918 and 1922. The former had an estimated magnitude of Mw 7.5 [12], though there was no report of tsunami inundation at Chafaral. The latter had a magnitude of Mw 8.3 [45], with the tsunami at Chafaral beginning one hour after the earthquake and three large waves being observed, reaching up to 10 m above mean sea level [13]. Therefore, a combination of the two events would appear to be a conservative approach to estimate the hazard.  
Since the extreme river flood events in 2015 and 2017 generated significant coastal morphology changes and erosion, and the official tsunami inundation map dated from 2014, the present study included the results of tsunami numerical simulations to update the tsunami hazard map. These simulations took into account the coastal morphology changes, as presented by [PERSON] et al, (2018) [46]. The numerical simulations were run by means of the Non-hydrostatic Evolution of Ocean WAVEs model (NEOWAVE) [47; 48]. The model generates the initial sea surface deformation, propagation and inundation by means of several nested grids which also include co-seismic deformations. They used 5 nested grids, with the highest grid resolution being \(\sim\)10 m. The level 5 grid was derived from several bathymetry and topography sources, such as the nautical chart N\({}^{\circ}\) 2213, a post-2017 detailed bathymetry provided by the Ministry of Public Works, post-2015 Lidar Topography with a resolution of 1 m contour lines provided by the Municipality of Chafaral, and a topography survey carried out by the authors themselves during august 2017 along the beach [46].  
Figure 3: Comparison between the situation after the May 2017 floods (**left**), ©Agencia Uno, and the current conditions in Chafaral in August 2017 (**right**), photos taken by the authors.  
The tsunami scenario was assumed to be the same as the one used for drawing the previous hazard map, i.e. an earthquake of magnitude Mw 8.6 in front of the town of Chanaral. The source parameters were a rupture length of 380 km, a rupture width of 130 km and a uniform slip of 8 m. The tide level was defined as the maximum high tide of +1.0 m. Figure 4 shows the results of the tsunami numerical simulations, namely the tsunami inundation height and tsunami waveform at a location close to the coastline. The results of [PERSON] et al. [46], show that the maximum runup can reach up to 15 m and significant parts of the coastal community can be flooded by the tsunami (Figure 4a). It was also observed that the first tsunami wave can arrive within 15 min of the earthquake and that three large waves could strike the town, with the second one being the largest (Figure 4b). The maximum inundation given by the numerical simulation is similar to the inundation given by SHOA (Hydrographic and Oceanographic Service of the Chilean Navy, in its Spanish acronym) [44], prior to the 2015 river flooding. Therefore, the morphological changes that have taken place due to the flooding do not appear to have a significant effect on potential future tsunami inundation.