Mw 9.3 Near West Coast of Northern Sumatra, Indonesia
updated 5 May 2022

On 26 December 2004 a great earthquake occurred near the West coast of Northern Sumatra, Indonesia at a depth of 10 km. The seismic event occurred at 00:58:50 UTC and had an estimated moment magnitude (Mw) 9.3 according to the EMSC. The USGS estimated a magnitude 9.1. It was the second/third largest earthquake in recorded history, surpassed only by the great Valdivia earthquake (Mw 9.5) in 1960 and arguably the great Alaska earthquake (Mw 9.2) in 1964. The great earthquake on 26 December 2004 is also referred to as the Boxing Day earthquake. It ruptured a fault length of 1300 km between Northern Sumatra and the Andaman Islands and caused major tsunamis in several countries around the Northeastern Indian Ocean, including Sumatra, Thailand, Sri Lanka and India. The total number of fatalities is estimated to be around 230,000.

Planetary geometry became critical on 19 December when Mercury aligned with the Sun and Neptune, converging with a high lunar peak (index 18). On the 23rd Mercury also aligned with the Sun and Uranus during the next lunar peak, partially due to the Moon-Earth-Mars alignment. Most critical was the Sun-Venus-Mars alignment early on the 26th that followed on the Mercury alignments (compare with the great Sanriku earthquake of 869). In addition, critical geometry involving Mercury and Venus occurred on the 24th, which is more obvious on the SUM graph below.


Mercury-Sun-Neptune       2004-12-19, 16:43:04  314°44'13"
Mercury-Sun-Uranus        2004-12-23, 20:55:24  336°00'46"
Sun-Venus-Mars            2004-12-26,  1:49:20  219°36'28"
Venus-Mercury-Earth       2004-12-28, 17:56:53   74°58'31"

Moon-Earth-Jupiter        2004-12-20,  3:12:25  195°55'20"
Moon-Earth-Mars           2004-12-23, 13:30:06  238°29'55"
Moon-Earth-Venus          2004-12-24, 11:42:28  249°38'58"
Moon-Earth-Mercury        2004-12-24, 15:58:45  251°47'05"
Moon-Earth-Sun            2004-12-26, 14:56:14  275°07'32"
SSGI chart
SSGI COMMON graph of critical planetary (PG) and lunar (LG) geometry

SSGI chart
SSGI SUM graph of critical planetary (PG) geometry