Largest events on the USGS list
The USGS table ranks the 22 May 1960 Valdivia earthquake at M9.5, epicenter 38.14°S, 73.41°W, time 19:11 UTC. That is number one on the list of the 20 largest earthquakes since 1900. The same table includes later and earlier events along the South American coast. Magnitudes and coordinates below are copied from that table.
| Earthquake | Mag | Time (UTC) | Epicenter |
|---|---|---|---|
| 1960 M9.5 Valdivia, Chile | 9.5 | 1960-05-22 19:11 UTC | -38.14, -73.41 |
| 2010 M8.8 Maule, Chile | 8.8 | 2010-02-27 06:34 UTC | -36.12, -72.9 |
| 1922 M8.5 Atacama, Chile | 8.5 | 1922-11-11 04:33 UTC | -28.29, -69.85 |
Two other South American rows on that USGS list are not Chilean-margin events. The 2001 M8.4 Arequipa, Peru earthquake and the 1906 M8.8 Ecuador–Colombia earthquake are on the Peru and northern Andes page.
Volcanoes on the same margin
Villarrica is in the Southern Andean Volcanic Arc in the Smithsonian snapshot. Cotopaxi is in the Northern Andean Volcanic Arc. Both fall in this site’s South America rectangle (latitude −56 to 5, longitude −85 to −65). The 1906 M8.8 epicenter near the Ecuador–Colombia coast is a different point from Cotopaxi’s summit coordinate. Use the distance tool if you want the kilometer gap. The gap is not a coupling factor and not a forecast.
What “Chile trench” means here
Searchers use “Chile trench” for the subduction margin where these great earthquakes occurred. This page uses the USGS locations and the Smithsonian volcano rows. It does not digitize the trench. A trench is a seafloor feature. An epicenter is a point estimate for one earthquake. A volcano is a catalog point. Mixing them into one line would look more precise than the sources are.