1960 Valdivia earthquake
The 1960 Valdivia earthquake () or Great Chilean earthquake ("Gran terremoto de Chile") of 22 May is the most powerful earthquake ever recorded. Various studies have placed it at 9.4–9.6 on the moment magnitude scale. It occurred in the afternoon (19:11 GMT, 15:11 local time), and lasted approximately 10 minutes. The resulting tsunami affected southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia and the Aleutian Islands.
Grotta Gigante horizontal pendulums
The movements of the pendulums has contributed to identify the free oscillations of the Earth, and to show that the secular term tilting of the cave is towards the northwest. The marine tides of the Adriatic have a loading effect in the cave, as have also the underground carstic floods of the river Timavo that disappears at the Skocjanske Cave in Slovenia. The Grotta Gigante tiltmeters are the only existing instruments to have recorded four out of five greatest earthquakes in the recent 50 years, which are the earthquakes of Chile 1960 (the greatest earthquake ever instrumentally recorded) and Chile 2010 (the fifth in the scale of recorded worldwide mega-events) the tsunami-generating event of the Sumatra-Andaman islands of 2004 (third greatest event) and the event of Japan 2011 (fourth greatest event), allowing an absolute-amplitude comparison between these events.