1833 Sumatra earthquake
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| Date | November 25, 1833 |
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| Magnitude | 8.8–9.2 Mw |
| Epicenter | 2°30′S 100°30′E / 2.5°S 100.5°ECoordinates: 2°30′S 100°30′E / 2.5°S 100.5°E |
| Areas affected | Sumatra, Dutch East Indies |
| Casualties | unknown |
The 1833 Sumatra earthquake occurred on November 25 at about 22:00 local time, with an estimated magnitude in the range of 8.8–9.2 Mw. It caused a large tsunami that flooded the southwestern coast of the island. There are no reliable records of the loss of life, with the casualties being described only as 'numerous'. The magnitude of this event has been estimated using records of uplift taken from coral microatolls.
The island of Sumatra lies on the convergent plate boundary between the Indo-Australian Plate and the Eurasian Plate. The convergence between these plates is highly oblique near Sumatra, with the displacement being accommodated by near pure dip-slip faulting along the subduction zone, known as the Sunda megathrust, and near pure strike-slip faulting along the Great Sumatran fault. The major slip events on the subduction zone interface are typically of megathrust type. Historically, great or giant megathrust earthquakes have been recorded in 1797, 1833, 1861, 2004, 2005 and 2007, most of them being associated with devastating tsunamis. Smaller (but still large) megathrust events have also occurred in the small gaps between the areas that slip during the larger events, in 1935, 1984, 2000 and 2002.
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