On 21 May 1960 a great earthquake occurred in Bio-Bio, Chile at a depth of 25 km. The seismic event occurred at 10:02:57 UTC and had an estimated moment magnitude (Mw) 8.1. It was followed a day later by a mega-thrust earthquake (Mw 9.5) in the same region.
On 17 May the planetary conjunction Mercury-Sun-Earth occurred, which was followed several hours later by the Sun's 90° with Mercury and Mars. An initial seismic increase occurred at the Ryukyu Islands, Japan (Mw 6.5) and Mauritius-Reunion Region (Mw 6.1). On the 20th the planetary conjunction Venus-Sun-Neptune occurred, immediately followed by a lunar peak, which resulted in a strong earthquake at Norfolk Island, Australia Region (Mw 6.5). The planetary conjunction with Venus was followed a day later by Mars-Mercury-Uranus while the Moon conjuncted Mars several hours earlier. This geometry is comparable to 1964. The great earthquake occurred around the same time. After Venus' 90° with Earth and Uranus and the planetary conjunction Mercury-Sun-Jupiter early on the 22nd, strong to major tremors followed in the region ranging from Mw 6.8 to Mw 7.8, which finally led to a mega-thrust earthquake (Mw 9.5), also known as the great Chilean or Valdivia earthquake.
Mercury-Sun-Neptune 1960-05-14, 11:55:39 218°25'22" Mercury-Sun-Earth 1960-05-17, 15:04:11 237°15'07" Venus-Sun-Neptune 1960-05-20, 12:29:24 218°27'30" Mars-Mercury-Uranus 1960-05-21, 15:05:56 141°42'49" Mercury-Sun-Jupiter 1960-05-22, 8:32:19 266°57'27" Mercury: Earth-Uranus 1960-05-15, 2:42:36 90°00'00" Sun: Mercury-Mars 1960-05-18, 3:47:35 90°00'00" Venus: Earth-Uranus 1960-05-22, 4:16:55 90°00'00" Earth-Moon-Jupiter 1960-05-14, 1:59:31 273°17'27" Earth-Moon-Saturn 1960-05-15, 3:06:44 288°44'08" Moon-Earth-Uranus 1960-05-17, 3:55:48 137°43'14" Earth-Moon-Mars 1960-05-20, 22:49:12 7°53'36" Moon-Earth-Neptune 1960-05-23, 7:58:55 217°39'49"