Peru has been the location for many large and damaging earthquakes since historical records began, most of which triggered devastating tsunamis.
The country lies above the convergent boundary where the Nazca Plate is subducting beneath the South American Plate at a rate of sixty-one millimeters per year.
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 on the moment magnitude scale, is 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.
The earthquake completely destroys the city of Lima in three to four minutes, also destroying Callao and everything else along the central Peruvian coast from Chancay in the north to Cañete in the south.
In Lima, all offices and all seventy-four churches are either damaged or destroyed leaving just twenty-five of the original three thousand houses standing.
Only eleven hundred and forty-one out of the population of sixty thousand die in Lima from the earthquake shaking, despite the amount of damage.
This is attributed to the intensity of the shaking increasing as the earthquake went on, giving the inhabitants the chance to escape.
The total number of casualties, including those from the tsunami, is almost six thousand, although some chroniclers give higher figures for Lima, partly due to the inclusion of the effects of subsequent epidemics.
Significant damage from the earthquake affects an area of about forty-four thousand square kilometers and it is felt up to seven hundred and fifty kilometers away.
The estimated rupture length is three hundred and fifty kilometers.
There are at least two hundred aftershocks observed in the first twenty-four hours after the main shock, out of a total of seventeen hundred recorded in the following one hundred and twelve days, although they cause no further casualties or significant damage.