The effects of the November 1, 1755 “Lisbon” earthquake in Morocco

Abstract

The “Lisbon” earthquake of November 1, 1755, the effects of which have been described at length in the Iberian Peninsula, was likewise strongly felt in Morocco, especially on the Atlantic coast, which was laid waste not only through the direct agency of seismic waves, but also through that of a formidable tsunami. The study of these effects in Morocco, based on a critical analysis of European and Arab sources entailing, whenever possible, a consultation of the original sources, has lead to the hypothesis that two distinct destructive earthquakes would have followed the main shock of November 1; one, on November 18, 1755, was probably an aftershock of the November 1 event and originated in the Gorringe Bank; the other, on November 27, 1755, was located in the Meknes area and is supposed to have destroyed that town. The values of intensities interpreted from the observations of the November 1 event have been compared with the values derived from the attenuation laws obtained from the recent earthquake of February 28, 1969 originating at the same source, the Moroccan isoseismals of which are well established. Extrapolated isoseismals for the effects of the November 1, 1755 event in Morocco as derived from this study are then assigned