Historical and geological sources for ancient earthquakes in the Iberian Peninsula

A critical review on the quality and quantity of historical and geological sources for ancient earthquakes in Spain is done. Recent critical reviews of the macroseismic catalogue for historical earthquakes of the Spanish National Geographic Institute (IGN; 2002) evidence a fragile reliability on the historical sources for the most ancient earthquakes in the Iberian Peninsula. In fact, after these criticisms the most recent review of the on-line IGN Spanish Catalogue during the year 2017, totally removed all the earthquakes occurred "Before the Common Era" (BCE) and most of those reported during de first millennia (< 1000 CE). For this last time-span only the Sagunto Earthquake (348 CE) and those documented by Arabic sources in the Cordoba Caliphate after 800 CE remained (9 events). The reasons for this removal is that most of the ancient earthquakes catalogued in Spain are originally documented in Cronica general de Espana written by the historian Florian de Ocampo in 1543, during the kingdom of Carlos I of Spain, who did not refer to older historic documents. However, the research developed for this paper clearly indicates that the work of Ocampo is based on the previous chronicles, such as Estoria de Espana written by the King of Castilla Alphonso X in c. 1280 CE, in turn based on a series of medieval chronicles (881-1236 CE) and on Greco-Roman writers. On the other hand, the seismic history of Spain with only 9 events cataloged before 1000 CE strongly contrast with the growing amount of geological and archaeological data evidencing strong seismic events during the antiquity and roman times. To contrast these different data-sources, ancient key events of the Spanish Catalogue are discussed here, such those occurred in the Pyrenees (880 and 500 BCE), the earthquake-tsunami event in the gulf of Cadiz in 218 BCE) and two earthquakes occurred during the end of the first millennium in Cordoba (881 CE) and northwest of the Iberian Peninsula (939 CE). The virtual absence of earthquakes in Spain before 1000 CE provide an unreal macroseismic scenario for the antiquity. This nearly aseismic scenario contrasts with the about 150 earthquakes (felt) per year catalogued for the period 1500-1800 CE, but also with the growing number of geoamhaeological data on ancient earthquakes in Spain published during the last years.