Mw 8.0 Haida Gwaii (Queen Charlotte Islands)
updated 22 August 2021

On 22 August 1949 a great earthquake occurred at Haida Gwaii (formerly Queen Charlotte Islands) at a depth of 10 km. The seismic event occurred at 04:01:18 UTC and had an estimated moment magnitude (Mw) 8.0.

No planetary alignments preceded the earthquake, but Earth was close to Mars-Jupiter. As a result, the Moon aligned with both outer planets just hours apart a day after the moon had also lined up with Uranus. This resulted in a high lunar peak (index 18) on the 20th and 21st, after which the earthquake occurred. Note that there was some critical planetary geometry (red peaks) preceding the lunar peak.

Earth-Moon-Uranus         1949-08-20,  4:42:37   94°35'32"
Earth-Moon-Mars           1949-08-21,  7:55:05  109°55'57"
Moon-Earth-Jupiter        1949-08-21, 15:26:44  294°16'44"
SSGI chart
SSGI depiction of planetary (PG) and lunar (LG) geometry