An estimated magnitude 8.7 earthquake causes a tsunami that damages more than 1,000 km (620 mi) of Chile's coastline.

The 1730 Valparaíso earthquake occurred at 04:45 local time on July 8. It had an estimated magnitude of 9.1–9.3 and triggered a major tsunami with an estimated magnitude of M_t  8.75, that inundated the lower parts of Valparaíso. The earthquake caused severe damage from La Serena to Chillan, while the tsunami affected more than 1,000 km (620 mi) of Chile's coastline.

A tsunami is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event.