The estimated moment magnitude 8.3–8.9 earthquake had an epicenter offshore in the Atlantic Ocean, and was felt in Lisbon at 00:40 local time.

Between the Strait of Gibraltar and Azores is where the African (Nubian), and Eurasian Plates meet along the Azores–Gibraltar Transform Fault.

Past estimates of the event have assigned a magnitude of between 6.7 and 7.6, with a macroseismic intensity of IV to VI at Lisbon and Seville.

On the Azores Islands, American historian William Hickley Prescott wrote in a letter that violent shaking continued for 3.5 minutes, seriously damaging homes and other structures.

[8] Much information and observations of the event in Lisbon is nonexistent due to the aftermath of the Napoleonic Wars, and the ongoing famine associated with the Year Without a Summer.