1746 Lima–Callao earthquake
 Lima
Arica
 |
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| Date | 28 October 1746 |
|---|---|
| Origin time | 03:30 UTC |
| Magnitude | 8.6–8.8 Mw |
| Epicenter | 11°21′S 77°17′W / 11.35°S 77.28°WCoordinates: 11°21′S 77°17′W / 11.35°S 77.28°W |
| Areas affected | Peru |
| Max. intensity | XI (Extreme) |
| Tsunami | Yes |
| Casualties | 5,941 |
The 1746 Lima–Callao earthquake occurred at 22:30 local time on 28 October with a moment magnitude of 8.6–8.8 and a maximum Mercalli intensity of XI (Extreme). The epicenter was located about 90 km (56 mi) north-northwest of the capital Lima, which was almost completely destroyed, and the subsequent tsunami devastated the port city of Callao. It was the deadliest earthquake in Peru’s history prior to the 1970 earthquake.
Peru lies above the convergent boundary where the Nazca Plate is subducting beneath the South American Plate at a rate of 61 mm per year. It has been the location for many large and damaging earthquakes since historical records began, most of which triggered devastating tsunamis. The southern segment of the Peruvian part of this plate boundary is affected by the presence of the Nazca aseismic ridge, on the downgoing plate. It also marks a major change in the subduction geometry between 'flat-slab' subduction to the northwest and normally dipping subduction to the southeast. The ridge appears to act as a barrier to rupture propagation, reducing the potential earthquake magnitude. The 1746 earthquake is interpreted to be a megathrust event that ruptured the whole of the northern segment of the plate interface within this zone.
The earthquake, with an estimated magnitude of 8.6–8.8 Mw, was the largest to strike central Peru in recorded history, and the second largest of all time, after the 1868 Arica earthquake in the south of the country. Significant damage from the earthquake affected an area of about 44,000 square kilometers and it was felt up to 750 km away. The estimated rupture length was 350 km. There were at least 200 aftershocks observed in the first 24 hours after the mainshock, out of a total of 1,700 recorded in the following 112 days, although they caused no further casualties or significant damage.
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