Preparation of subduction Earthquakes : Slow, Deep, Large-scale trigger. DeepTrigger is a project funded by the European Research Council. The aim of the project is to study the preparation of subduction earthquakes in the Chile/Peru subduction area. The seismological network deployed in Chile (XZ network) is composed of 25 stations medium-band velocimeter (Guralp CMG40-60s and Nanometrics Trillium-Compact-PostHole-20s). Those 25 stations will be deployed during ~3 years in middle area of Chile (Network code XZ) from mid-2021 to mid-2024. The targeted area in North-Central Chile (27°S-30°S) is located just north of the 2015 Illapel rupture. It is a recognized ‘seismic gap’, where the last earthquakes of Mw8.5+ occurred in1819 and 1922, and where a future large event is to be expected. The area is characterized by an interseismic coupling that evolves from low in the south to high in the north (Métois et al., 2018), and where deep slow slip events have been recently discovered (Klein et al., 2018). This is therefore an excellent target to study the preparation of a future large earthquake, the lateral interactions between large seismic ruptures, and the link between slow slip and the seismic response to slow slip. The installed seismological network will provide key data to investigate these questions. Precise catalogues of seismicity will be generated, in which swarm, repeaters and clusters will be identified and analysed. LFEs and tremors will also be systematically scanned, catalogued and analysed.