March 30, 1761 Earthquake: Lisbon, Porto, Portugal

Earthquake at Lisbon, Portugal occurred at 12:01 a.m. local time. Baptista et al. (Reference #3952) concluded after their study of historical documents and data, that this earthquake's epicenter was located about 34.5 deg N and 13 deg W. They give the magnitude as 8.5. Lander et al. (Reference #537) locates the event further north at 37 deg N and 10 deg W, and estimates an intensity of IX.

Mallet and Mallet (Reference #1897) report the earthquake was felt: "At Lisbon, Setuval, Oporto, and all along the coast of Portugal; at Madrid, Aranjuez, etc. in Spain. Some vessels at sea off Lisbon...experienced the shocks. At Santa Cruz in Barbary; at Bayonne, Bordeaus, and Roussillon in France; at Amsterdam in Holland; at Cork in Ireland; at Funchal and throughout the island of Maderia; and at the Azores."

March 31, 1761, Lisbon, Portugal, intensity IX. (ref #1093)

March 31, 1761, 12:01 (local time), W. Cabo San Vicente, Portugal, 37 N, 10 W. (ref #1193)

March 31, 1761. With the exception of the earthquake of 1755, this was probably the strongest of the whole series. Though violent in Lisbon, there was little, if any, loss of life there, a few old houses were shattered or thrown down and the walls of some new ones cracked.

The shock is said to have been felt at Oporto and all along the coast of at Portugal, in Spain at Madrid and Aranjuez, in France at Bayonne, Bordeaus and Rousillon, and even so far as Amsterdam, Cork, Funchal and through Madeira, the Azores and the Canary Islands. Little confidence can be placed in reports from such outlying places. Possibly, the epicentre lay some distance to the west of Lisbon, an inference that seems supported by the clearly great extent of the disturbed area (of, say, half a million or a million sq. miles), the comparatively slight intensity of the shock there, and the small number of recorded aftershocks.

The earthquake occurred at 0.5 p.m., and, as in that of 1755, it was of great estimated duration-5 min. at Lisbon, 3 min. at Aranjuez and Bayonne, and 23 min. at Madrid.

The effects of the earthquake were manifest far beyond the bounds of the disturbed area, but were much less widely noticed than in 1755. At Fort Augustus, at about a p.m., the surface of Loch Ness rose suddenly about 2 ft. and continued to rise and fall for 45 min. According to another account from the same place, the movements began between noon and 1 p.m. and lasted half an hour, the rise in the level being nearly 30 in. In Amsterdam, the chandelier in one church was seen to vibrate at some time between 1 and 2 p.m., that in another moved about a foot from the vertical line through the point of support.

The number of aftershocks felt in Lisbon must have been small, and this points to a considerable distance between the city and the epicentral area. Several shocks were felt during the next three days, all of them slight but one, a severe shock, on Apr. 3 at 2 a.m.

(above from ref #516)

a strong earthquake that affected the Iberian Peninsula without serious damage, although in Lisbon it was stronger and some buildings collapsed. (ref #12938)

Although with a lower intensity than the 1755 earthquake, it destroyed many of the ruins from the previous catastrophe (Borlase [1762] 1830). The earthquake was felt with violence throughout the Portuguese mainland, in the Azores and Madeira archipelagos and even as far as Madrid (Spain), Cork (Ireland), Amsterdam (Netherlands), the Canary islands and Barbados (Borlase [1762] 1830; Perrey 1847; Mallet and Mallet 1858; Milne 1899). Nevertheless, this event is not reported by any of the contemporary Portuguese chroniclers, according to Borlase ([1762] 1830), as a consequence of the terror that dominated the country following the recent 1755 catastrophe. (ref #13057)

25 deaths, magnitude 6.7 Mw (ref#12773)